CA2346733C - Omnidirectional reflective multilayer device for confining electromagnetic radiation - Google Patents
Omnidirectional reflective multilayer device for confining electromagnetic radiation Download PDFInfo
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- PORWMNRCUJJQNO-UHFFFAOYSA-N tellurium atom Chemical compound [Te] PORWMNRCUJJQNO-UHFFFAOYSA-N 0.000 claims description 7
- 230000001419 dependent effect Effects 0.000 claims description 6
- 239000011521 glass Substances 0.000 claims description 5
- 229910052732 germanium Inorganic materials 0.000 claims description 3
- GNPVGFCGXDBREM-UHFFFAOYSA-N germanium atom Chemical compound [Ge] GNPVGFCGXDBREM-UHFFFAOYSA-N 0.000 claims description 3
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Classifications
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- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
- G02B6/02—Optical fibres with cladding with or without a coating
- G02B6/02295—Microstructured optical fibre
- G02B6/023—Microstructured optical fibre having different index layers arranged around the core for guiding light by reflection, i.e. 1D crystal, e.g. omniguide
- G02B6/02304—Core having lower refractive index than cladding, e.g. air filled, hollow core
-
- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
- G02B6/10—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings of the optical waveguide type
- G02B6/102—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings of the optical waveguide type for infrared and ultraviolet radiation
Abstract
A device having at least one dielectric inner core region in which electromagnetic radiation is confined, and at least two dielectric outer regions surrounding the inner core region, each with a distinct refractive index. The outer regions confine electromagnetic radiation within the inner core region. The refractive indices, the number of outer regions, and thickness of the outer regions result in a reflectivity for a planar geometry that is greater than 95 % for angles of incidence ranging from 0° to at least 80°
for all polarizations for a range of wavelengths of the electromagnetic radiation. In exemplary embodiments, the inner core region is made of a low dielectric material, and the outer regions include alternating layers of low and high dielectric materials. In one aspect of the invention, the device is a waveguide, and in another aspect the device is a microcavity. One embodiment describes a polystyrene-tellurium multilayer coating for the infrared and it is used on a hollow waveguide.
for all polarizations for a range of wavelengths of the electromagnetic radiation. In exemplary embodiments, the inner core region is made of a low dielectric material, and the outer regions include alternating layers of low and high dielectric materials. In one aspect of the invention, the device is a waveguide, and in another aspect the device is a microcavity. One embodiment describes a polystyrene-tellurium multilayer coating for the infrared and it is used on a hollow waveguide.
Description
OMNIDIRECTIONAL REFLECTIVE MULTILAYER DEVICE FOR CONFINING
ELECTROMAGNETIC RADIATION
BACKGROUND OF THE INVENTION
The invention relates to the field of optical waveguiding, and in particular to an omnidirectional multilayered device for enhanced waveguiding of electromagnetic radiation.
Mirrors are probably the most prevalent of optical devices. Known to the ancients and used by them as objects of worship and beauty, mirrors are currently employed for imaging, solar energy collection and in laser cavities. Their intriguing optical properties have captured the imagination of scientists as well as artists and writers.
One can distinguish between two types of mirrors, the age-old metallic, and more recent dielectric. Metallic mirrors reflect light over a broad range of frequencies incident from arbitrary angles, i.e., omnidirectional reflectance. However, at infrared and optical frequencies, a few percent of the incident power is typically lost due to absorption.
Multilayer dielectric mirrors are used primarily to reflect a narrow range of frequencies incident from a particular angle or particular angular range. Unlike their metallic counterparts, dielectric reflectors can be extremely low loss.
The ability to reflect light of arbitrary angle of incidence for all-dielectric structures has been associated with the existence of a complete photonic bandgap, which can exist only in a system with a dielectric function that is periodic along three orthogonal directions. In fact, a recent theoretical analysis predicted that a sufficient condition for the achievement of omnidirectional reflection in a periodic system with an interface is the existence of an overlapping bandgap regime in phase space above the light cone of the ambient media.
The theoretical analysis is now extended to provide experimental realization of a multilayer omnidirectional reflector operable in infrared frequencies.
The structure is made of thin layers of materials with difference dielectric constants (polystyrene and tellurium) and combines characteristic features of both the metallic and dielectric mirrors.
It offers metallic-like omnidirectional reflectivity together with frequency selectivity and low-loss behaviour typical of multilayer dielectrics.
ELECTROMAGNETIC RADIATION
BACKGROUND OF THE INVENTION
The invention relates to the field of optical waveguiding, and in particular to an omnidirectional multilayered device for enhanced waveguiding of electromagnetic radiation.
Mirrors are probably the most prevalent of optical devices. Known to the ancients and used by them as objects of worship and beauty, mirrors are currently employed for imaging, solar energy collection and in laser cavities. Their intriguing optical properties have captured the imagination of scientists as well as artists and writers.
One can distinguish between two types of mirrors, the age-old metallic, and more recent dielectric. Metallic mirrors reflect light over a broad range of frequencies incident from arbitrary angles, i.e., omnidirectional reflectance. However, at infrared and optical frequencies, a few percent of the incident power is typically lost due to absorption.
Multilayer dielectric mirrors are used primarily to reflect a narrow range of frequencies incident from a particular angle or particular angular range. Unlike their metallic counterparts, dielectric reflectors can be extremely low loss.
The ability to reflect light of arbitrary angle of incidence for all-dielectric structures has been associated with the existence of a complete photonic bandgap, which can exist only in a system with a dielectric function that is periodic along three orthogonal directions. In fact, a recent theoretical analysis predicted that a sufficient condition for the achievement of omnidirectional reflection in a periodic system with an interface is the existence of an overlapping bandgap regime in phase space above the light cone of the ambient media.
The theoretical analysis is now extended to provide experimental realization of a multilayer omnidirectional reflector operable in infrared frequencies.
The structure is made of thin layers of materials with difference dielectric constants (polystyrene and tellurium) and combines characteristic features of both the metallic and dielectric mirrors.
It offers metallic-like omnidirectional reflectivity together with frequency selectivity and low-loss behaviour typical of multilayer dielectrics.
SUMMARY OF THE INVENTION
According to one aspect of the invention, there is provided a device comprising: a dielectric inner core surrounded by an outer dielectric region comprising a plurality of alternating layers of high-index and low-index dielectric materials, the outer dielectric region confining electromagnetic radiation to the inner core region, wherein the refractive indices of the dielectric materials, the number of the alternating layers in the outer dielectric regions, and the thicknesses of the alternating layers result in a reflectivity that is greater than 95% for all angles of incidence from the inner core region to the outer dielectric region ranging from 0° to at least 80° for all polarizations for at least one range of frequencies of the electromagnetic radiation, the at least one range of frequencies dependent on the refractive indices of the dielectric materials and the thicknesses of the alternating layers, and wherein sin-' ( n~ I n y )< tan-' ( n, l n, ), no < n, , and n~ <
n, where no is the I S refractive index of the dielectric inner core, n, is the refractive index of the high-index dielectric material layer, and n, is the refractive index of the low-index dielectric material layer.
According to another aspect of the invention, there is provided a waveguide which exhibits omnidirectional reflection, comprising: a dielectric inner core region surrounded by an outer dielectric region comprising a plurality of alternating layers of high-index and low-index dielectric materials, the outer dielectric region confining electromagnetic radiation to the inner core region, wherein the refractive indices of the dielectric materials, the number of the alternating layers in the outer dielectric regions, and the thicknesses of the alternating layers result in a reflectivity that is greater than 95% for all angles of incidence from the inner core region to the outer dielectric region ranging from 0°
to at least 80° for all polarizations for at least one range of frequencies of the electromagnetic radiation, the at least one range of frequencies dependent on the refractive indices of the dielectric materials and the thicknesses of the alternating layers, and wherein sin' ( n~ /n, )< tan-' ( n, l n2 ), n~ < n, , and no < n, , where no is the refractive index of the dielectric inner core, n, is the refractive index of the high-index dielectric material layer, and n, is the refractive index of the low-index dielectric material layer.
-2a-According to another aspect of the invention, there is provided a device comprising: a dielectric inner core region surrounded by an outer dielectric region comprising a plurality of alternating layers of high-index and low-index dielectric materials, the outer dielectric region confining electromagnetic radiation to the inner core region, wherein the layers in the outer dielectric layer define a refractive index variation that produce a range of frequencies for which there is omnidirectional reflection for electromagnetic radiation incident on the dielectric outer region from the dielectric inner core region, the range of frequencies for which there is omnidirectional reflection being defined from above by an upper frequency denoted as ~h corresponding to a photonic band edge for normally incident electromagnetic radiation and from below by a lower frequency denoted as ~, corresponding to an intersection between a photonic band edge for TM
electromagnetic radiation and a light line defined by the dielectric inner core region, wherein coi, and con are dependent on the refractive indices of the dielectric material and the thicknesses of the alternating layers, and wherein sin-' ( no /n, )< tan-' ( n, l n, ), n~ < n, , and no < n, , where n~ is the refractive index of the dielectric inner core, n, is the refractive index of the high-index dielectric material layer, and n, is the refractive index of the low-index dielectric material layer.
According to another aspect of the invention, there is provided a device comprising: a dielectric inner core region surrounded by an outer dielectric region comprising a plurality of alternating layers of high-index and low-index dielectric materials, the outer dielectric region confining electromagnetic radiation to the inner core region, wherein the refractive index of the dielectric inner core regions is n~ , the refractive indices of the high-index and low-index materials are n, and n, , respectively, the thicknesses of the high-index and low-index layers are h, and h, , respectively, and n, > n, > no , wherein the indices satisfy sin-' ( no /n2 )< tan-' ( n, l n, ), and wherein the indices and thicknesses are selected so as to satisfy, ~,, > ~, , where w,, and ~, are two predetermined frequencies given by the respective expressions:
-2b-2c _, n, - n2 cos , h2nz + h, n, n, + n2 2c cos-' n' nz n° n2 n? no h2 n2 - no + h~ n; - no n; n2 - no + n2 n; - no whereby the outer dielectric region reflects the electromagnetic radiation for all angles of incidence within a predetermined angle range when the frequency of the electromagnetic radiation cv is in the range from coi to coh.
According to another aspect of the invention, there is provided a device for confining electromagnetic radiation, comprising: a dielectric inner core region in which the electromagnetic radiation is to be confined, the inner core region having a refractive index no , an outer dielectric region surrounding the inner core region to confine the electromagnetic radiation within the inner core region, the outer dielectric region including a plurality of alternating layers of high-index and low-index dielectric materials surrounding the core region, wherein the refractive indices of the high-index and low-index materials are n, and n, , respectively, the thicknesses of the high-index and low-index layers are h, and h, , respectively, and n, > n, > no , wherein the refractive indices and thicknesses are selected so as to satisfy, ~,, > ~, , where ~,, and r.~, are two predetermined frequencies given by the respective expressions:
2c _, n, - nz cos , and hZn2 + h,n, n, + n2 2c cos-' n' n2 n° n2 n' no h2 n2 - no + h, n; - no n; n2 - no + n2 n; - no to provide a range of frequencies between the predetermined frequencies co, to co,, for which the alternating layers provide omnidirectional reflectivity for electromagnetic radiation incident on the alternating layers from the inner core region, and wherein the number of -2 c-alternating layers are sufficient to cause omnidirectional reflectivity to be greater than 95%
electromagnetic radiation incident on the alternating layers from the inner core region at all angles ranging from 0° to 80° and all polarizations for all frequencies in the omindirectional range of frequencies between co, to co,,.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a simplified block diagram of an exemplary embodiment of a multilayer periodic dielectric film structure in accordance with the invention;
FIG. 2A is a graph of the projected band structure of a multilayer film with a light line and Brewster line, exhibiting a reflectivity range of limited angular acceptance;
FIG. 2B is a graph of the projected band structure of a multilayer film together with the light line and Brewster line, showing an omnidirectional reflectance range at the first and second harmonic;
FIG. 3 is a graph of the range to midrange ratio for the fundamental frequency range of omnidirectional reflection plotted as contours;
FIG. 4 is a series of graphs showing the calculated (solid line) and measured (dashed line) reflectance (%) as a function of wavelength for TM and TE modes at normal, 45°, and 80° angles of incidence, thus showing an omnidirectional reflectivity band;
FIG. 5 is a table showing that ~ is a monotonically increasing function of the incident angle for the TM mode of an omnidirectional reflector;
FIG. 6A is a simplified block diagram cross section of an exemplary structure FIG. 6B is a corresponding cross section radial index of refraction profile of the struchu~e in FIG. 6A; and FIG. 7 is a cross section of a simplified schematic diagram of a coextrusion assembly in accordance with the invention.
DETAILED DESCRIPTION OF THE INVENTION
FIG. 1 is a simplified block diagram of an exemplary embodiment of a muitilayer periodic dielectric film structure 100 in accordance with the invention. The structure is made of an array of alternating dielectric layers 102,104 coupled to a homogeneous medium, characterized by no (such as air with no = 1 ), at the interfaces.
Electromagnetic waves are incident upon the multilayer film from the homogeneous medium. The possibility of omnidirectional reflectivity for such a system has now been recognized. h, and h2 are the layer thickness , and n, and n_ are the indices of refraction of the respective layers 104 and 102.
An exemplary incident wave has a wave vector k = kxex + kyey and frequency of w = c~k~ . The wave vector together with the normal to the periodic structure 100 defines a minor plane of symmetry that allows distinguishing between two independent electromagnetic modes: transverse electric (TE) modes and transverse magnetic (TM) 2 0 modes. For the TE mode, the electric field is perpendicular to the plane, as is the magnetic field for the TM mode. The distribution of the electric field of the TE mode (or the magnetic field in the TM mode) in a particular layer within the stratified structure can be written as a sum of two plane waves traveling in opposite directions. The amplitudes of the two plane waves in a particular layer a of one cell are related to the amplitudes in the same layer of an adjacent cell by a unitary 2x2 translation matrix U~"~
General features of the transport properties of the finite structure can be understood when the properties of the infinite structure are elucidated. In a structure with infinite number of layers, translational symmetry along the direction perpendicular to the layers leads to Bloch wave solutions of the form iKx ikry E,~ ~x, y) = E,~ (x~ a , where Ex (x) is periodic, with a period of length a, and K is the Bloch wave number given by K= aln ~Tr(U~°~)~ 4(Tr(U~°~)Z -1)l (2) where Tr denotes the trace operation, which yields the sum of the diagonal matrix elements.
Solutions of the infinite system can be propagating or evanescent, corresponding to real or imaginary Bloch wave numbers, respectively. The solution of Eq. 2 defines the band structure for the infinite system, cu (K,ky).
It is convenient to display the solutions of the infinite structure by projecting the w (K,ky) function onto the w - ky plane. FIGs. 2A and 2B are examples of such projected structures.
FIG. 2A is a graph of the projected band structure of a multilayer film with a light line 200 and Brewster line 202, exhibiting a reflectivity range of limited angular acceptance with n1 = 2.2 and n2 = 1.7, and a thickness ratio of h2 / hl = 2.2 / 1.7.
FIG. 2B is a graph of the projected band structure of a multilayer film together with the light line 204 and Brewster line 206, showing an omnidirectional reflectance range at the first and second harmonic. The film parameters are n1 = 4.6 and n2 = 1.6 with a thickness ratio of h2 / hl = 1.6 / 0.8. These parameters are similar to the actual polymer-tellurium film parameters measured in the experiment.
The area 208 and 210 (light gray) highlight phase space where K is strictly real, i.e., regions of propagating states. The area 212 (white) represents regions containing evanescent states. The areas 214 and 216 represent omnidirectional reflectance ranges.
The shape of the projected band structures for the multilayer film structure can be understood intuitively. At ky = 0 the bandgap for waves travelling normal to the layers is recovered. For ky > 0, the bands curve upward in frequency. As ky ~
oo , the modes become largely confined to the slabs with the high index of refraction and do not ~5 rrnmla llPtWlP! n lavPre ~an~l arP thPrPfnrP mrlananrlPnt of lrxl -4a-For a finite structure, the translational symmetry in the directions parallel to the layers is preserved, hence ky remains a conserved quantity. In the direction perpendicular to the layers, the translational symmetry no longer exists. Nevertheless, the K
number, as defined in Eq. 2, is still relevant, because it is determined purely by the dielectric and structural property of a single bilayer. In regions where K is imaginary, the electromagnetic field is strongly attenuated. As the number of layers is increased, the transmission coefficient _________ __________~:_»__ ___tm_ n__ __n__~:__:~__ _~___.._t_.. __~:4_.
According to one aspect of the invention, there is provided a device comprising: a dielectric inner core surrounded by an outer dielectric region comprising a plurality of alternating layers of high-index and low-index dielectric materials, the outer dielectric region confining electromagnetic radiation to the inner core region, wherein the refractive indices of the dielectric materials, the number of the alternating layers in the outer dielectric regions, and the thicknesses of the alternating layers result in a reflectivity that is greater than 95% for all angles of incidence from the inner core region to the outer dielectric region ranging from 0° to at least 80° for all polarizations for at least one range of frequencies of the electromagnetic radiation, the at least one range of frequencies dependent on the refractive indices of the dielectric materials and the thicknesses of the alternating layers, and wherein sin-' ( n~ I n y )< tan-' ( n, l n, ), no < n, , and n~ <
n, where no is the I S refractive index of the dielectric inner core, n, is the refractive index of the high-index dielectric material layer, and n, is the refractive index of the low-index dielectric material layer.
According to another aspect of the invention, there is provided a waveguide which exhibits omnidirectional reflection, comprising: a dielectric inner core region surrounded by an outer dielectric region comprising a plurality of alternating layers of high-index and low-index dielectric materials, the outer dielectric region confining electromagnetic radiation to the inner core region, wherein the refractive indices of the dielectric materials, the number of the alternating layers in the outer dielectric regions, and the thicknesses of the alternating layers result in a reflectivity that is greater than 95% for all angles of incidence from the inner core region to the outer dielectric region ranging from 0°
to at least 80° for all polarizations for at least one range of frequencies of the electromagnetic radiation, the at least one range of frequencies dependent on the refractive indices of the dielectric materials and the thicknesses of the alternating layers, and wherein sin' ( n~ /n, )< tan-' ( n, l n2 ), n~ < n, , and no < n, , where no is the refractive index of the dielectric inner core, n, is the refractive index of the high-index dielectric material layer, and n, is the refractive index of the low-index dielectric material layer.
-2a-According to another aspect of the invention, there is provided a device comprising: a dielectric inner core region surrounded by an outer dielectric region comprising a plurality of alternating layers of high-index and low-index dielectric materials, the outer dielectric region confining electromagnetic radiation to the inner core region, wherein the layers in the outer dielectric layer define a refractive index variation that produce a range of frequencies for which there is omnidirectional reflection for electromagnetic radiation incident on the dielectric outer region from the dielectric inner core region, the range of frequencies for which there is omnidirectional reflection being defined from above by an upper frequency denoted as ~h corresponding to a photonic band edge for normally incident electromagnetic radiation and from below by a lower frequency denoted as ~, corresponding to an intersection between a photonic band edge for TM
electromagnetic radiation and a light line defined by the dielectric inner core region, wherein coi, and con are dependent on the refractive indices of the dielectric material and the thicknesses of the alternating layers, and wherein sin-' ( no /n, )< tan-' ( n, l n, ), n~ < n, , and no < n, , where n~ is the refractive index of the dielectric inner core, n, is the refractive index of the high-index dielectric material layer, and n, is the refractive index of the low-index dielectric material layer.
According to another aspect of the invention, there is provided a device comprising: a dielectric inner core region surrounded by an outer dielectric region comprising a plurality of alternating layers of high-index and low-index dielectric materials, the outer dielectric region confining electromagnetic radiation to the inner core region, wherein the refractive index of the dielectric inner core regions is n~ , the refractive indices of the high-index and low-index materials are n, and n, , respectively, the thicknesses of the high-index and low-index layers are h, and h, , respectively, and n, > n, > no , wherein the indices satisfy sin-' ( no /n2 )< tan-' ( n, l n, ), and wherein the indices and thicknesses are selected so as to satisfy, ~,, > ~, , where w,, and ~, are two predetermined frequencies given by the respective expressions:
-2b-2c _, n, - n2 cos , h2nz + h, n, n, + n2 2c cos-' n' nz n° n2 n? no h2 n2 - no + h~ n; - no n; n2 - no + n2 n; - no whereby the outer dielectric region reflects the electromagnetic radiation for all angles of incidence within a predetermined angle range when the frequency of the electromagnetic radiation cv is in the range from coi to coh.
According to another aspect of the invention, there is provided a device for confining electromagnetic radiation, comprising: a dielectric inner core region in which the electromagnetic radiation is to be confined, the inner core region having a refractive index no , an outer dielectric region surrounding the inner core region to confine the electromagnetic radiation within the inner core region, the outer dielectric region including a plurality of alternating layers of high-index and low-index dielectric materials surrounding the core region, wherein the refractive indices of the high-index and low-index materials are n, and n, , respectively, the thicknesses of the high-index and low-index layers are h, and h, , respectively, and n, > n, > no , wherein the refractive indices and thicknesses are selected so as to satisfy, ~,, > ~, , where ~,, and r.~, are two predetermined frequencies given by the respective expressions:
2c _, n, - nz cos , and hZn2 + h,n, n, + n2 2c cos-' n' n2 n° n2 n' no h2 n2 - no + h, n; - no n; n2 - no + n2 n; - no to provide a range of frequencies between the predetermined frequencies co, to co,, for which the alternating layers provide omnidirectional reflectivity for electromagnetic radiation incident on the alternating layers from the inner core region, and wherein the number of -2 c-alternating layers are sufficient to cause omnidirectional reflectivity to be greater than 95%
electromagnetic radiation incident on the alternating layers from the inner core region at all angles ranging from 0° to 80° and all polarizations for all frequencies in the omindirectional range of frequencies between co, to co,,.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a simplified block diagram of an exemplary embodiment of a multilayer periodic dielectric film structure in accordance with the invention;
FIG. 2A is a graph of the projected band structure of a multilayer film with a light line and Brewster line, exhibiting a reflectivity range of limited angular acceptance;
FIG. 2B is a graph of the projected band structure of a multilayer film together with the light line and Brewster line, showing an omnidirectional reflectance range at the first and second harmonic;
FIG. 3 is a graph of the range to midrange ratio for the fundamental frequency range of omnidirectional reflection plotted as contours;
FIG. 4 is a series of graphs showing the calculated (solid line) and measured (dashed line) reflectance (%) as a function of wavelength for TM and TE modes at normal, 45°, and 80° angles of incidence, thus showing an omnidirectional reflectivity band;
FIG. 5 is a table showing that ~ is a monotonically increasing function of the incident angle for the TM mode of an omnidirectional reflector;
FIG. 6A is a simplified block diagram cross section of an exemplary structure FIG. 6B is a corresponding cross section radial index of refraction profile of the struchu~e in FIG. 6A; and FIG. 7 is a cross section of a simplified schematic diagram of a coextrusion assembly in accordance with the invention.
DETAILED DESCRIPTION OF THE INVENTION
FIG. 1 is a simplified block diagram of an exemplary embodiment of a muitilayer periodic dielectric film structure 100 in accordance with the invention. The structure is made of an array of alternating dielectric layers 102,104 coupled to a homogeneous medium, characterized by no (such as air with no = 1 ), at the interfaces.
Electromagnetic waves are incident upon the multilayer film from the homogeneous medium. The possibility of omnidirectional reflectivity for such a system has now been recognized. h, and h2 are the layer thickness , and n, and n_ are the indices of refraction of the respective layers 104 and 102.
An exemplary incident wave has a wave vector k = kxex + kyey and frequency of w = c~k~ . The wave vector together with the normal to the periodic structure 100 defines a minor plane of symmetry that allows distinguishing between two independent electromagnetic modes: transverse electric (TE) modes and transverse magnetic (TM) 2 0 modes. For the TE mode, the electric field is perpendicular to the plane, as is the magnetic field for the TM mode. The distribution of the electric field of the TE mode (or the magnetic field in the TM mode) in a particular layer within the stratified structure can be written as a sum of two plane waves traveling in opposite directions. The amplitudes of the two plane waves in a particular layer a of one cell are related to the amplitudes in the same layer of an adjacent cell by a unitary 2x2 translation matrix U~"~
General features of the transport properties of the finite structure can be understood when the properties of the infinite structure are elucidated. In a structure with infinite number of layers, translational symmetry along the direction perpendicular to the layers leads to Bloch wave solutions of the form iKx ikry E,~ ~x, y) = E,~ (x~ a , where Ex (x) is periodic, with a period of length a, and K is the Bloch wave number given by K= aln ~Tr(U~°~)~ 4(Tr(U~°~)Z -1)l (2) where Tr denotes the trace operation, which yields the sum of the diagonal matrix elements.
Solutions of the infinite system can be propagating or evanescent, corresponding to real or imaginary Bloch wave numbers, respectively. The solution of Eq. 2 defines the band structure for the infinite system, cu (K,ky).
It is convenient to display the solutions of the infinite structure by projecting the w (K,ky) function onto the w - ky plane. FIGs. 2A and 2B are examples of such projected structures.
FIG. 2A is a graph of the projected band structure of a multilayer film with a light line 200 and Brewster line 202, exhibiting a reflectivity range of limited angular acceptance with n1 = 2.2 and n2 = 1.7, and a thickness ratio of h2 / hl = 2.2 / 1.7.
FIG. 2B is a graph of the projected band structure of a multilayer film together with the light line 204 and Brewster line 206, showing an omnidirectional reflectance range at the first and second harmonic. The film parameters are n1 = 4.6 and n2 = 1.6 with a thickness ratio of h2 / hl = 1.6 / 0.8. These parameters are similar to the actual polymer-tellurium film parameters measured in the experiment.
The area 208 and 210 (light gray) highlight phase space where K is strictly real, i.e., regions of propagating states. The area 212 (white) represents regions containing evanescent states. The areas 214 and 216 represent omnidirectional reflectance ranges.
The shape of the projected band structures for the multilayer film structure can be understood intuitively. At ky = 0 the bandgap for waves travelling normal to the layers is recovered. For ky > 0, the bands curve upward in frequency. As ky ~
oo , the modes become largely confined to the slabs with the high index of refraction and do not ~5 rrnmla llPtWlP! n lavPre ~an~l arP thPrPfnrP mrlananrlPnt of lrxl -4a-For a finite structure, the translational symmetry in the directions parallel to the layers is preserved, hence ky remains a conserved quantity. In the direction perpendicular to the layers, the translational symmetry no longer exists. Nevertheless, the K
number, as defined in Eq. 2, is still relevant, because it is determined purely by the dielectric and structural property of a single bilayer. In regions where K is imaginary, the electromagnetic field is strongly attenuated. As the number of layers is increased, the transmission coefficient _________ __________~:_»__ ___tm_ n__ __n__~:__:~__ _~___.._t_.. __~:4_.
Since the primary interest is in waves originating from the homogeneous medium external to the periodic structure, the focus will be only on the portion of phase space lying above the light line. Waves originating from the homogeneous medium satisfy the condition w >_ cky l no, where no is the refractive index of the homogeneous medium, and therefore they must reside above the light line. States of the homogeneous medium with ky = 0 are normal incident, and those lying on the w = cky l no line with kx =
0 are incident at an angle of 90°.
The states in FIG. 2A that are lying in the restricted phase space defined by the light line 200 and that have a (w , k y ) corresponding to the propagating solutions (gray areas 208) of the structure can propagate in both the homogeneous medium and in the structure. These waves will partially or entirely transmit through the film.
Those with (w, ky) in the evanescent regions (white areas 212) can propagate in the homogeneous medium, but will decay in the structure. Waves corresponding to this portion of phase space will be reflected off the structure.
The multilayer system leading to FIGS. 2A represents a structure with a limited reflectivity cone since for any frequency one can always find a ky vector for which a wave at that frequency can propagate in the structure, and hence transmit through the film.
For example, a wave with w = 0.285 2~cla (dashed horizontal line 218) will be reflected for a range of ky values ranging from 0 (normal incidence) to 0.285 2n/a (90° incidence) 2 0 in the TE mode, while in the TM mode it begins to transmit at a value of ky = 0.187 2~/a ('41° incidence). The necessary and sufficient criterion for omnidirectional reflectivity at a given frequency is that there exist no transmitting states of the structure inside the Light cone. This criterion is satisfied by frequency ranges 214 and 216 in FIG. 2B. In fact, the system leading to FIG. 2B exhibits two omnidirectional reflectivity ranges.
A necessary condition for omnidirectional reflectivity is that light from outside of the structure cannot be allowed to access the Brewster angle 6 B = tan-' (n, l n2 ) of the multilayer structure because at this angle, the TM mode will be transmitted through. This condition is met when the Brewster line lies outside of the light line, or, terms of the refractive indices of the layers, siu-' (»o / n?) < AB . A sufficient condition is the existence 3 0 of a particular frequency at which no propagating mode within the crystal exists between ky =Oand ky =wlc.
0 are incident at an angle of 90°.
The states in FIG. 2A that are lying in the restricted phase space defined by the light line 200 and that have a (w , k y ) corresponding to the propagating solutions (gray areas 208) of the structure can propagate in both the homogeneous medium and in the structure. These waves will partially or entirely transmit through the film.
Those with (w, ky) in the evanescent regions (white areas 212) can propagate in the homogeneous medium, but will decay in the structure. Waves corresponding to this portion of phase space will be reflected off the structure.
The multilayer system leading to FIGS. 2A represents a structure with a limited reflectivity cone since for any frequency one can always find a ky vector for which a wave at that frequency can propagate in the structure, and hence transmit through the film.
For example, a wave with w = 0.285 2~cla (dashed horizontal line 218) will be reflected for a range of ky values ranging from 0 (normal incidence) to 0.285 2n/a (90° incidence) 2 0 in the TE mode, while in the TM mode it begins to transmit at a value of ky = 0.187 2~/a ('41° incidence). The necessary and sufficient criterion for omnidirectional reflectivity at a given frequency is that there exist no transmitting states of the structure inside the Light cone. This criterion is satisfied by frequency ranges 214 and 216 in FIG. 2B. In fact, the system leading to FIG. 2B exhibits two omnidirectional reflectivity ranges.
A necessary condition for omnidirectional reflectivity is that light from outside of the structure cannot be allowed to access the Brewster angle 6 B = tan-' (n, l n2 ) of the multilayer structure because at this angle, the TM mode will be transmitted through. This condition is met when the Brewster line lies outside of the light line, or, terms of the refractive indices of the layers, siu-' (»o / n?) < AB . A sufficient condition is the existence 3 0 of a particular frequency at which no propagating mode within the crystal exists between ky =Oand ky =wlc.
FIG. 2A is an example of a structure, which does not have an omnidirectional reflectivity range even though its Brewster crossing is inaccessible to light coming from the homogeneous medium (the Brewster crossing lies outside of the light cone). This is due to the large group velocity of modes in the lower band edge of the TM
mode which allow every frequency to couple to a propagating state in the crystal. This should be contrasted with FIG 2B, which exhibits an omnidirectional reflectivity (area 214).
The high indices of refraction actually allow for the opening of an additional omnidirectional reflectivity range (area 216) in the higher harmonic as well.
The omnidirectional range is defined from above by the normal incidence band edge ~h ~kx = ~ l a, ky = 0~ (point 220), and below by the intersection of the top of the TM allowed band edge with the light line ~~ ~kx = ~ l a, ky = noc~, l c~
(point 222). The exact expression for the band edges is 1 2n cos~kX'~h, + k~z~hz )+ 1 2n cos~kx'~h, - kXZ~hz ~+ 1= 0, (3) s where kx"~ = pvna l c)2 - ky ~a = l, 2) and _1 k~2~ k~'~
2 k~'~ + k~z~ TE
x x _1 nzk~2~ nZk~'~ ~4) x z x TM.
2 nZk~'~ + n2k~2~
2 x 1 x -6a-A dimensionless parameter used to quantify the extent of the omnidirectional reflection range is the range to midrange ratio defined as ~~h - to, ~l ~ ~r~h + to, ~.
FIG. 3 is a plot of this ratio as a function of n2 / n, and n, l n° where r,~h and w, are determined by solutions of Eq. 3 with quarter wave layer thickness, and n2 )n, . The contours in this figure represent various equi-omnidirectional ranges for different material index parameters and could be useful for design purposes. The ratio for the exemplary materials is approximately 45% ~n, l n2 = 2.8?5, n2 ! n° =1.6~, and it is located at the intersection of the dashed lines at point 300.
It may also be usefi~l to have an approximate analytical expression for the extent of the gap, where the "gap" is the frequency range between the edges of the allowed bands. This can be obtained by setting cos~kx'~h, - kxz~h2 ~ ~ 1 in Eq. 3. It is found that for a ~...us.~ .w..:~7.....4 ......'1.. ~ 41.... ..._."...,_._~....~._ __.:.14L ~~
L~.._~___~-__ _-_'7_ 0~~90 ) = 2c cos-' n + 1 - cos-' n + 1 ~ ~5) z z ~ z z-nzsi z8 h~ n~ - no stn Io + hz nz ° n o At normal incidence there is no distinction between TM and TE modes. At increasingly oblique angles the gap of the TE mode increases, whereas the gap of the TM
mode decreases. In addition, the center of the gap shifts to higher frequencies.
Therefore, the criterion for the existence of omnidirectional reflectivity can be restated as the occurrence of a frequency overlap between the gap at normal incidence and the gap of the TM
mode at 90° . Analytic expressions for the range to midrange ratio can be obtained by setting 2c _, n, - nz toh = cos , hznz + h,n, n1 + nz (6) - 2c cos-' n' nz n° nz n' no hz n2 no + h, n; no n; n2 no + ni n~ no Moreover, the maximum range width is attained for thickness values that are not equal to the quarter wave stack though the increase in bandwidth gained by deviating from the quarter wave stack is typically only a few percent.
In general, the TM mode defines the lower frequency edge of the omnidirectional range. An example can be seen in FIG. 2B for a particular choice of the indices of refraction. This can be proven by showing that a~ ~ a~
ax ax Y TM y TE
-7a-in the region that resides inside the light line. The physical reason for Eq.
mode which allow every frequency to couple to a propagating state in the crystal. This should be contrasted with FIG 2B, which exhibits an omnidirectional reflectivity (area 214).
The high indices of refraction actually allow for the opening of an additional omnidirectional reflectivity range (area 216) in the higher harmonic as well.
The omnidirectional range is defined from above by the normal incidence band edge ~h ~kx = ~ l a, ky = 0~ (point 220), and below by the intersection of the top of the TM allowed band edge with the light line ~~ ~kx = ~ l a, ky = noc~, l c~
(point 222). The exact expression for the band edges is 1 2n cos~kX'~h, + k~z~hz )+ 1 2n cos~kx'~h, - kXZ~hz ~+ 1= 0, (3) s where kx"~ = pvna l c)2 - ky ~a = l, 2) and _1 k~2~ k~'~
2 k~'~ + k~z~ TE
x x _1 nzk~2~ nZk~'~ ~4) x z x TM.
2 nZk~'~ + n2k~2~
2 x 1 x -6a-A dimensionless parameter used to quantify the extent of the omnidirectional reflection range is the range to midrange ratio defined as ~~h - to, ~l ~ ~r~h + to, ~.
FIG. 3 is a plot of this ratio as a function of n2 / n, and n, l n° where r,~h and w, are determined by solutions of Eq. 3 with quarter wave layer thickness, and n2 )n, . The contours in this figure represent various equi-omnidirectional ranges for different material index parameters and could be useful for design purposes. The ratio for the exemplary materials is approximately 45% ~n, l n2 = 2.8?5, n2 ! n° =1.6~, and it is located at the intersection of the dashed lines at point 300.
It may also be usefi~l to have an approximate analytical expression for the extent of the gap, where the "gap" is the frequency range between the edges of the allowed bands. This can be obtained by setting cos~kx'~h, - kxz~h2 ~ ~ 1 in Eq. 3. It is found that for a ~...us.~ .w..:~7.....4 ......'1.. ~ 41.... ..._."...,_._~....~._ __.:.14L ~~
L~.._~___~-__ _-_'7_ 0~~90 ) = 2c cos-' n + 1 - cos-' n + 1 ~ ~5) z z ~ z z-nzsi z8 h~ n~ - no stn Io + hz nz ° n o At normal incidence there is no distinction between TM and TE modes. At increasingly oblique angles the gap of the TE mode increases, whereas the gap of the TM
mode decreases. In addition, the center of the gap shifts to higher frequencies.
Therefore, the criterion for the existence of omnidirectional reflectivity can be restated as the occurrence of a frequency overlap between the gap at normal incidence and the gap of the TM
mode at 90° . Analytic expressions for the range to midrange ratio can be obtained by setting 2c _, n, - nz toh = cos , hznz + h,n, n1 + nz (6) - 2c cos-' n' nz n° nz n' no hz n2 no + h, n; no n; n2 no + ni n~ no Moreover, the maximum range width is attained for thickness values that are not equal to the quarter wave stack though the increase in bandwidth gained by deviating from the quarter wave stack is typically only a few percent.
In general, the TM mode defines the lower frequency edge of the omnidirectional range. An example can be seen in FIG. 2B for a particular choice of the indices of refraction. This can be proven by showing that a~ ~ a~
ax ax Y TM y TE
-7a-in the region that resides inside the light line. The physical reason for Eq.
7 lies in the vectorial nature of the electric field. In the upper portion of the first band the electric field concentrates its energy in the high dielectric regions.
Away from normal incidence the electric field in the TM mode has a component in the direction of periodicity. This component forces a larger portion of the electric field into the low dielectric regions. The group velocity of the TM
mode is therefore enhanced. In contrast, the electric field of the TE mode is always perpendicular to the direction of periodicity and can concentrate its energy primarily in the high dielectric 1 d region.
A polystyrene-tellurium (PS-Te) materials system was chosen to demonstrate omnidirectional reflectivity. Tellurium has a high index of refraction and low loss _g_ characteristics in the frequency range of interest. In addition, its relatively low latent heat of condensation together with the high glass transition temperature of the PS
minimizes diffusion of Te into the polymer layer. The choice of PS, which has a series of absorption peaks in the measurement range, demonstrates the competition between reflectivity and absorption that occurs when an absorption peak is located in the evanescent state region.
The Te(0.8pm) and PS (1.65pm) films were deposited sequentially to create a nine-layer film.
A 0.8 ~ 0.09pm thick layer of tellurium (99.99 + %, Strem Chemicals) was vacuum evaporated at 10-6 torr and 7A (Ladd Industries 30000) onto a NaCI 25mm salt substrate (polished NaCI window, Wilmad Glass). The layer thickness and deposition rate were monitored in-situ using a crystal thickness monitor (Sycon STM100). A 10%
solution of polystyrene (Goodyear PS standard, 110,OOOg/mol) in toluene was spin cast at 1000RPM onto the tellurium coated substrate and allowed to dry for a few hours, the polymer layer thickness is 1.65 ~ 0.09qm. The nine layer film sequence was Te/PS/Te/PS/Te/PS/Te/PS/Te.
The optical response of this particular multilayer film was designed to have a high reflectivity region in the 10 to 15~m range for any angle of incidence (in the experiment we measure from 0° to 80°). The optical response at oblique angles of incidence was measured using a Fourier Transform Infrared Spectrometer (Nicolet 860) fitted with a polarizer (ZnS SpectraTech) and an angular reflectivity stage (VeeMax by SpectraTech). At normal incidence, the reflectivity was measured using a Nicolet Infrared Microscope. A freshly evaporated aluminum mirror was used as a background for the reflectance measurements.
FIG. 4 is a series of graphs showing the calculated (solid line) and measured (dashed line) reflectance (%) as a function of wavelength for TM and TE modes at normal, 45°, and 80° angles of incidence, thus showing an omnidirectional reflectivity band. FIG. 4 illustrates the good agreement between the calculated and measured reflectance spectra. The calculations were done using the transfer matrix method described in F. Abeles, Ann. De Physique 5, 706 (1950).
The regimes of high reflectivity at the different angles of incidence overlap, thus forming a reflective range of frequencies for light of any angle of incidence. The frequency location of the omnidirectional range is determined by the layer thickness and can be tuned to meet specifications. The range is calculated from Eq. 6 to be 5.6 ~,m and the center wavelength is 12.4 ~m corresponding to a 45% range to midrange ratio shown in dashed lines in FIG. 3 for the experimental index of refraction parameters.
These values are in agreement with the measured data. The calculations are for lossless media and therefore do not predict the PS absorption band at ~ 13 and 14 microns. The PS
absorption peak is seen to increase at larger angles of incidence for the TM mode, and decrease for the TE
mode.
The physical basis for this phenomena lies in the relation between the penetration depth and the amount of absorption. The penetration length is ~ oc Im (1 / K), with K the Bloch wave number. It can be shown that ~ is a monotonically increasing function of the incident angle for the TM mode of an omnidirectional reflector, and is relatively constant for the TE mode. Thus, the TM mode penetrates deeper into the structure at increasing angles of incidence and is more readily absorbed, as is shown in the table of FIG. 5. The magnitude of the imaginary part of the Bloch wave number for a mode lying in the gap is related to its distance from the band edges. This distance increases in the TE mode due to the widening of the gap at increasing angles of incidence and decreases in the TM mode due to the shrinking of the gap.
The PS-Te structure does not have a complete photonic bandgap. Its 2 0 omnidirectional reflectivity is due instead to the restricted phase space available to the propagating states of the system. The materials and processes were chosen for their low cost and applicability to large area coverage. In addition to omnidirectionality, the measurements show that a polymer, while lossy in the infrared, can still be used for -9a-reflection applications without a considerable sacrifice of performance. The possibility of achieving omnidirectional reflectivity itself is not associated with any particular choice of material and can be applied to many wavelengths of interest. The structure of the invention offers metallic-like omnidirectional reflectivity for a wide range of frequencies, and at the same time is of low loss. In addition, it allows the flexibility of frequency selection.
In accordance with the invention, the confinement of light in cavities and wave guides using an omnidirectional multilayer film will now be described.
The multilayer film structure has been described in commonly owned U.S. Patent No. 6,130,780, issued October 10, 2000. Specifically, a method is presented for creating low loss broad band optical fibers, which are capable of transmitting around sharp bids.
In addition, a design is presented for improving the delivering power of a near field optical fiber tip.
FIG. 6A is a simplified block diagram cross section of an exemplary structure 600.
FIG. 6B is a corresponding cross section radial index of refiaction profile of the structure 600. The structure consists of concentric cylindrical layers 604-616 with alternating indices of refraction n,, n2 centered on a core 602 of low dielectric material no , such as air. The radius of the core is ha and the layer thicknesses are h" hz . Note that an exemplary embodiment would involve each layer consisting of different material and corresponding different layer thickness. 1fie parameters of the multilayer film are chosen such that light from any incident angle and polarization is completely reflected by the multilayer for the range of signal frequencies.
For example, for values of no, n,, n~, h,, and hZ as in FIG. 2B, light can be guided for any frequency within the two broadband omnidirectional reflection ranges 214 and 216. As is generally the case, the electromagnetic radiation will be mufti-mode or singie mode depending an the size of the region in which it is confined. Thus, within each broadband range the electromagnetic radiation can be mufti-mode or single mode depending on the size of the inner core region. For large core radii, the light will be mufti-mode and for very small radii the light will be single mode.
Conventional optical fibers confine a propagating EM pulse by total internal reflection where the electromagnetic (EM) wave travels through a high index fiber core surrounded by low-index cladding. In accordance with the invention, the method of confinement in the OmniguideT"' waveguide structure is the polarization independent omnidirectional reflectance of EM waves at the walls of the hollow fiber. The advantages of this mode of confinement are numerous.
There is very low loss associated with material absorption since the wave travels essentially through air, which is extremely low loss when compared with any dense medium. This enables low loss propagation which is of importance in basically every device that involves light guiding for communication, lasers and more.
3 0 Conventional optical communication fibers need amplification to compensate for absorption losses in the material, and to this end, the fiber is periodically doped with erbium. The use of erbium severely limits the bandwidth of the fiber. Since the structure of the invention is very low loss and does not need amplification, orders of magnitude increase in the usable bandwidth is possible. In addition, the omnidirectional multilayer structure provides a strong confinement mechanism and will propagate signals around very sharp bends as demonstrated in other systems with strong confinement mechanisms.
Such a multilayer coated fiber will also be important for improving the delivering power of a fiber tip in a near-field scanning optical microscope. The tip is used to deliver optical power with a spot size far smaller than the wavelength of light. Metal coattng is currently employed in order to confine light to such a small length scale.
Metal coatings have material absorption losses, which in this case limits the maximum delivery power.
The fiber tip with a multilayer coating overcomes this problem since it is essentially 1 0 lossless.
The ultimate goal is to create a hollow structure with walls made of a multilayer coating in accordance with the structure described heretofore. The structure may be of, but is not limited to, a cylindrical geometry. One method to produce such a structure is to take a thin wall hollow fiber made of glass or polymer and coat it with alternating layers of dielectrics. The layers could be made of a polymer or glass as the low refiactive index component, and Germanium or Tellurium as the high index material. One would then take the fiber and evaporate a layer of prescribed thickness using a thermal evaporator or sputtering device. The subsequent low index layer would be deposited by dipping the fiber in a dilute solution of the polymer, or by evaporating a monomer 2 0 followed by a rapid polymerization.
Another exemplary method would be the coextrusion of the entire structure using a combination of immiscible polymers, one loaded with a high index component in a fine powder form the other without additives as in FIG. 7. FIG. 7 is a cross section of a simplified schematic diagram of a coextrusion assembly 700 in accordance with the invention. An extruding device 702 provides a structure 704 of alternating layers of high and low index polymer surrounding an air core 706.
Although the present invention has been shown and described with respect to several preferred embodiments thereof, various changes, omissions and additions to the form and detail thereof, may be made therein, without departing from the spirit and scope of the invention.
What is claimed is:
Away from normal incidence the electric field in the TM mode has a component in the direction of periodicity. This component forces a larger portion of the electric field into the low dielectric regions. The group velocity of the TM
mode is therefore enhanced. In contrast, the electric field of the TE mode is always perpendicular to the direction of periodicity and can concentrate its energy primarily in the high dielectric 1 d region.
A polystyrene-tellurium (PS-Te) materials system was chosen to demonstrate omnidirectional reflectivity. Tellurium has a high index of refraction and low loss _g_ characteristics in the frequency range of interest. In addition, its relatively low latent heat of condensation together with the high glass transition temperature of the PS
minimizes diffusion of Te into the polymer layer. The choice of PS, which has a series of absorption peaks in the measurement range, demonstrates the competition between reflectivity and absorption that occurs when an absorption peak is located in the evanescent state region.
The Te(0.8pm) and PS (1.65pm) films were deposited sequentially to create a nine-layer film.
A 0.8 ~ 0.09pm thick layer of tellurium (99.99 + %, Strem Chemicals) was vacuum evaporated at 10-6 torr and 7A (Ladd Industries 30000) onto a NaCI 25mm salt substrate (polished NaCI window, Wilmad Glass). The layer thickness and deposition rate were monitored in-situ using a crystal thickness monitor (Sycon STM100). A 10%
solution of polystyrene (Goodyear PS standard, 110,OOOg/mol) in toluene was spin cast at 1000RPM onto the tellurium coated substrate and allowed to dry for a few hours, the polymer layer thickness is 1.65 ~ 0.09qm. The nine layer film sequence was Te/PS/Te/PS/Te/PS/Te/PS/Te.
The optical response of this particular multilayer film was designed to have a high reflectivity region in the 10 to 15~m range for any angle of incidence (in the experiment we measure from 0° to 80°). The optical response at oblique angles of incidence was measured using a Fourier Transform Infrared Spectrometer (Nicolet 860) fitted with a polarizer (ZnS SpectraTech) and an angular reflectivity stage (VeeMax by SpectraTech). At normal incidence, the reflectivity was measured using a Nicolet Infrared Microscope. A freshly evaporated aluminum mirror was used as a background for the reflectance measurements.
FIG. 4 is a series of graphs showing the calculated (solid line) and measured (dashed line) reflectance (%) as a function of wavelength for TM and TE modes at normal, 45°, and 80° angles of incidence, thus showing an omnidirectional reflectivity band. FIG. 4 illustrates the good agreement between the calculated and measured reflectance spectra. The calculations were done using the transfer matrix method described in F. Abeles, Ann. De Physique 5, 706 (1950).
The regimes of high reflectivity at the different angles of incidence overlap, thus forming a reflective range of frequencies for light of any angle of incidence. The frequency location of the omnidirectional range is determined by the layer thickness and can be tuned to meet specifications. The range is calculated from Eq. 6 to be 5.6 ~,m and the center wavelength is 12.4 ~m corresponding to a 45% range to midrange ratio shown in dashed lines in FIG. 3 for the experimental index of refraction parameters.
These values are in agreement with the measured data. The calculations are for lossless media and therefore do not predict the PS absorption band at ~ 13 and 14 microns. The PS
absorption peak is seen to increase at larger angles of incidence for the TM mode, and decrease for the TE
mode.
The physical basis for this phenomena lies in the relation between the penetration depth and the amount of absorption. The penetration length is ~ oc Im (1 / K), with K the Bloch wave number. It can be shown that ~ is a monotonically increasing function of the incident angle for the TM mode of an omnidirectional reflector, and is relatively constant for the TE mode. Thus, the TM mode penetrates deeper into the structure at increasing angles of incidence and is more readily absorbed, as is shown in the table of FIG. 5. The magnitude of the imaginary part of the Bloch wave number for a mode lying in the gap is related to its distance from the band edges. This distance increases in the TE mode due to the widening of the gap at increasing angles of incidence and decreases in the TM mode due to the shrinking of the gap.
The PS-Te structure does not have a complete photonic bandgap. Its 2 0 omnidirectional reflectivity is due instead to the restricted phase space available to the propagating states of the system. The materials and processes were chosen for their low cost and applicability to large area coverage. In addition to omnidirectionality, the measurements show that a polymer, while lossy in the infrared, can still be used for -9a-reflection applications without a considerable sacrifice of performance. The possibility of achieving omnidirectional reflectivity itself is not associated with any particular choice of material and can be applied to many wavelengths of interest. The structure of the invention offers metallic-like omnidirectional reflectivity for a wide range of frequencies, and at the same time is of low loss. In addition, it allows the flexibility of frequency selection.
In accordance with the invention, the confinement of light in cavities and wave guides using an omnidirectional multilayer film will now be described.
The multilayer film structure has been described in commonly owned U.S. Patent No. 6,130,780, issued October 10, 2000. Specifically, a method is presented for creating low loss broad band optical fibers, which are capable of transmitting around sharp bids.
In addition, a design is presented for improving the delivering power of a near field optical fiber tip.
FIG. 6A is a simplified block diagram cross section of an exemplary structure 600.
FIG. 6B is a corresponding cross section radial index of refiaction profile of the structure 600. The structure consists of concentric cylindrical layers 604-616 with alternating indices of refraction n,, n2 centered on a core 602 of low dielectric material no , such as air. The radius of the core is ha and the layer thicknesses are h" hz . Note that an exemplary embodiment would involve each layer consisting of different material and corresponding different layer thickness. 1fie parameters of the multilayer film are chosen such that light from any incident angle and polarization is completely reflected by the multilayer for the range of signal frequencies.
For example, for values of no, n,, n~, h,, and hZ as in FIG. 2B, light can be guided for any frequency within the two broadband omnidirectional reflection ranges 214 and 216. As is generally the case, the electromagnetic radiation will be mufti-mode or singie mode depending an the size of the region in which it is confined. Thus, within each broadband range the electromagnetic radiation can be mufti-mode or single mode depending on the size of the inner core region. For large core radii, the light will be mufti-mode and for very small radii the light will be single mode.
Conventional optical fibers confine a propagating EM pulse by total internal reflection where the electromagnetic (EM) wave travels through a high index fiber core surrounded by low-index cladding. In accordance with the invention, the method of confinement in the OmniguideT"' waveguide structure is the polarization independent omnidirectional reflectance of EM waves at the walls of the hollow fiber. The advantages of this mode of confinement are numerous.
There is very low loss associated with material absorption since the wave travels essentially through air, which is extremely low loss when compared with any dense medium. This enables low loss propagation which is of importance in basically every device that involves light guiding for communication, lasers and more.
3 0 Conventional optical communication fibers need amplification to compensate for absorption losses in the material, and to this end, the fiber is periodically doped with erbium. The use of erbium severely limits the bandwidth of the fiber. Since the structure of the invention is very low loss and does not need amplification, orders of magnitude increase in the usable bandwidth is possible. In addition, the omnidirectional multilayer structure provides a strong confinement mechanism and will propagate signals around very sharp bends as demonstrated in other systems with strong confinement mechanisms.
Such a multilayer coated fiber will also be important for improving the delivering power of a fiber tip in a near-field scanning optical microscope. The tip is used to deliver optical power with a spot size far smaller than the wavelength of light. Metal coattng is currently employed in order to confine light to such a small length scale.
Metal coatings have material absorption losses, which in this case limits the maximum delivery power.
The fiber tip with a multilayer coating overcomes this problem since it is essentially 1 0 lossless.
The ultimate goal is to create a hollow structure with walls made of a multilayer coating in accordance with the structure described heretofore. The structure may be of, but is not limited to, a cylindrical geometry. One method to produce such a structure is to take a thin wall hollow fiber made of glass or polymer and coat it with alternating layers of dielectrics. The layers could be made of a polymer or glass as the low refiactive index component, and Germanium or Tellurium as the high index material. One would then take the fiber and evaporate a layer of prescribed thickness using a thermal evaporator or sputtering device. The subsequent low index layer would be deposited by dipping the fiber in a dilute solution of the polymer, or by evaporating a monomer 2 0 followed by a rapid polymerization.
Another exemplary method would be the coextrusion of the entire structure using a combination of immiscible polymers, one loaded with a high index component in a fine powder form the other without additives as in FIG. 7. FIG. 7 is a cross section of a simplified schematic diagram of a coextrusion assembly 700 in accordance with the invention. An extruding device 702 provides a structure 704 of alternating layers of high and low index polymer surrounding an air core 706.
Although the present invention has been shown and described with respect to several preferred embodiments thereof, various changes, omissions and additions to the form and detail thereof, may be made therein, without departing from the spirit and scope of the invention.
What is claimed is:
Claims (42)
1. A device comprising:
a dielectric inner core surrounded by an outer dielectric region comprising a plurality of alternating layers of high-index and low-index dielectric materials, the outer dielectric region confining electromagnetic radiation to said inner core region, wherein the refractive indices of the dielectric materials, the number of the alternating layers in the outer dielectric regions, and the thicknesses of the alternating layers result in a reflectivity that is greater than 95% for all angles of incidence from the inner core region to the outer dielectric region ranging from 0° to at least 80° for all polarizations for at least one range of frequencies of said electromagnetic radiation, the at least one range of frequencies dependent on the refractive indices of the dielectric materials and the thicknesses of the alternating layers, and wherein sin-1 (n0 /n2) < tan-1 (n1/n2), n0 < n1, and n0 < n2 where n0 is the refractive index of the dielectric inner core, n1 is the refractive index of the high-index dielectric material layer, and n2 is the refractive index of the low-index dielectric material layer.
a dielectric inner core surrounded by an outer dielectric region comprising a plurality of alternating layers of high-index and low-index dielectric materials, the outer dielectric region confining electromagnetic radiation to said inner core region, wherein the refractive indices of the dielectric materials, the number of the alternating layers in the outer dielectric regions, and the thicknesses of the alternating layers result in a reflectivity that is greater than 95% for all angles of incidence from the inner core region to the outer dielectric region ranging from 0° to at least 80° for all polarizations for at least one range of frequencies of said electromagnetic radiation, the at least one range of frequencies dependent on the refractive indices of the dielectric materials and the thicknesses of the alternating layers, and wherein sin-1 (n0 /n2) < tan-1 (n1/n2), n0 < n1, and n0 < n2 where n0 is the refractive index of the dielectric inner core, n1 is the refractive index of the high-index dielectric material layer, and n2 is the refractive index of the low-index dielectric material layer.
2. The device of claim 1, wherein said device comprises a circular cross section.
3. The device of claim 1, wherein said device comprises a rectangular cross section.
4. The device of claim 1, wherein said device comprises a triangular cross section.
5. The device of claim 1, wherein said device comprises a hexagonal cross section.
6. The device of any one of claims 1 to 5, wherein said inner core region comprises a low dielectric material.
7. The device of claim 6, wherein said inner core region comprises a gas.
8. The device of claim 7, wherein said inner core region comprises air.
9. The device of any one of claims 1 to 8, wherein said low dielectric material comprises a polymer or a glass.
10. The device of any one of claims 1 to 9, wherein said high dielectric material comprises germanium or tellurium.
11. The device of any one of claims 1 to 10, wherein the outer regions comprise alternating layers of dielectric and thin metal materials.
12. The device of any one of claims 1 to 11, wherein said device is utilized to guide high power electromagnetic radiation.
13. The device of any one of claims 1 to 11, wherein said device is utilized to guide high power electromagnetic radiation around bends.
14. The device of any one of claims 1 to 11, wherein said device is utilized as a microcavity to confine electromagnetic radiation.
15. A waveguide which exhibits omnidirectional reflection, comprising:
a dielectric inner core region surrounded by an outer dielectric region comprising a plurality of alternating layers of high-index and low-index dielectric materials, the outer dielectric region confining electromagnetic radiation to said inner core region, wherein the refractive indices of the dielectric materials, the number of the alternating layers in the outer dielectric regions, and the thicknesses of the alternating layers result in a reflectivity that is greater than 95% for all angles of incidence from the inner core region to the outer dielectric region ranging from 0° to at least 80° for all polarizations for at least one range of frequencies of said electromagnetic radiation, the at least one range of frequencies dependent on the refractive indices of the dielectric materials and the thicknesses of the alternating layers, and wherein sin-1 (n0 /n2) < tan-1 (n1/n2), n0 < n1, and n0 < n2, where n0 is the refractive index of the dielectric inner core, n1 is the refractive index of the high-index dielectric material layer, and n2 is the refractive index of the low-index dielectric material layer.
a dielectric inner core region surrounded by an outer dielectric region comprising a plurality of alternating layers of high-index and low-index dielectric materials, the outer dielectric region confining electromagnetic radiation to said inner core region, wherein the refractive indices of the dielectric materials, the number of the alternating layers in the outer dielectric regions, and the thicknesses of the alternating layers result in a reflectivity that is greater than 95% for all angles of incidence from the inner core region to the outer dielectric region ranging from 0° to at least 80° for all polarizations for at least one range of frequencies of said electromagnetic radiation, the at least one range of frequencies dependent on the refractive indices of the dielectric materials and the thicknesses of the alternating layers, and wherein sin-1 (n0 /n2) < tan-1 (n1/n2), n0 < n1, and n0 < n2, where n0 is the refractive index of the dielectric inner core, n1 is the refractive index of the high-index dielectric material layer, and n2 is the refractive index of the low-index dielectric material layer.
16. A device comprising:
a dielectric inner core region surrounded by an outer dielectric region comprising a plurality of alternating layers of high-index and low-index dielectric materials, the outer dielectric region confining electromagnetic radiation to said inner core region, wherein the layers in the outer dielectric layer define a refractive index variation that produce a range of frequencies for which there is omnidirectional reflection for electromagnetic radiation incident on the dielectric outer region from the dielectric inner core region, the range of frequencies for which there is omnidirectional reflection being defined from above by an upper frequency denoted as .omega. h corresponding to a photonic band edge for normally incident electromagnetic radiation and from below by a lower frequency denoted as .omega. corresponding to an intersection between a photonic band edge for TM electromagnetic radiation and a light line defined by the dielectric inner core region, wherein .omega.h and .omega.h are dependent on the refractive indices of the dielectric material and the thicknesses of the alternating layers, and wherein sin-1 (n0/n2) < tan-1(n1/n2), n0 < n1, and n0 < n2, where n0 is the refractive index of the dielectric inner core, n1 is the refractive index of the high-index dielectric material layer, and n2 is the refractive index of the low-index dielectric material layer.
a dielectric inner core region surrounded by an outer dielectric region comprising a plurality of alternating layers of high-index and low-index dielectric materials, the outer dielectric region confining electromagnetic radiation to said inner core region, wherein the layers in the outer dielectric layer define a refractive index variation that produce a range of frequencies for which there is omnidirectional reflection for electromagnetic radiation incident on the dielectric outer region from the dielectric inner core region, the range of frequencies for which there is omnidirectional reflection being defined from above by an upper frequency denoted as .omega. h corresponding to a photonic band edge for normally incident electromagnetic radiation and from below by a lower frequency denoted as .omega. corresponding to an intersection between a photonic band edge for TM electromagnetic radiation and a light line defined by the dielectric inner core region, wherein .omega.h and .omega.h are dependent on the refractive indices of the dielectric material and the thicknesses of the alternating layers, and wherein sin-1 (n0/n2) < tan-1(n1/n2), n0 < n1, and n0 < n2, where n0 is the refractive index of the dielectric inner core, n1 is the refractive index of the high-index dielectric material layer, and n2 is the refractive index of the low-index dielectric material layer.
17. The device of claim 16, wherein the refractive index variation produces a frequency range to midrange ratio, defined as (.omega.h-.omega.l)/[(1/2)(.omega.h+.omega.l)], that is greater than or equal to 10%.
18. The device of claim 16, wherein the refractive index variation produces a frequency range to midrange ratio, defined as (.omega.h-.omega.l)/[(1/2)(.omega.h+.omega.l)], that is greater than or equal to 20%.
19. The device of claim 16, wherein the refractive index variation produces a frequency range to midrange ratio, defined as (.omega.h-.omega.l)/[(1/2)(.omega.h+.omega.l)] that is greater than or equal to 30%.
20. The device of claim 16, wherein the refractive index variation produces a frequency range to midrange ratio, defined as (.omega.h_.omega.l)/[(1/2)(.omega.h+.omega.l)], that is greater than or equal to 40%.
21. The device of claim 1 or claim 16, wherein the dielectric inner core region extends along a waveguide axis and the outer dielectric region surrounds the waveguide axis.
22. A device comprising:
a dielectric inner core region surrounded by an outer dielectric region comprising a plurality of alternating layers of high-index and low-index dielectric materials, the outer dielectric region confining electromagnetic radiation to said inner core region, wherein the refractive index of the dielectric inner core regions is n0 , the refractive indices of the high-index and low-index materials are n1 and n2, respectively, the thicknesses of the high-index and low-index layers are h1 and h2, respectively, and n1 > n2 > n0, wherein the indices satisfy sin-1 (n0/n2) < tan-1(n1/n2), and wherein the indices and thicknesses are selected so as to satisfy, .omega.h >
.omega.l, where .omega.h, and .omega.l are two predetermined frequencies given by the respective expressions:
whereby the outer dielectric region reflects the electromagnetic radiation for all angles of incidence within a predetermined angle range when the frequency of the electromagnetic radiation .omega. is in the range from .omega.1 to .omega.h.
a dielectric inner core region surrounded by an outer dielectric region comprising a plurality of alternating layers of high-index and low-index dielectric materials, the outer dielectric region confining electromagnetic radiation to said inner core region, wherein the refractive index of the dielectric inner core regions is n0 , the refractive indices of the high-index and low-index materials are n1 and n2, respectively, the thicknesses of the high-index and low-index layers are h1 and h2, respectively, and n1 > n2 > n0, wherein the indices satisfy sin-1 (n0/n2) < tan-1(n1/n2), and wherein the indices and thicknesses are selected so as to satisfy, .omega.h >
.omega.l, where .omega.h, and .omega.l are two predetermined frequencies given by the respective expressions:
whereby the outer dielectric region reflects the electromagnetic radiation for all angles of incidence within a predetermined angle range when the frequency of the electromagnetic radiation .omega. is in the range from .omega.1 to .omega.h.
23. The device of claim 22, wherein the dielectric inner core region extends along a waveguide axis and the outer dielectric region surrounds the waveguide axis.
24. A device for confining electromagnetic radiation, comprising:
a dielectric inner core region in which the electromagnetic radiation is to be confined, the inner core region having a refractive index n0, an outer dielectric region surrounding the inner core region to confine the electromagnetic radiation within the inner core region, the outer dielectric region including a plurality of alternating layers of high-index and low-index dielectric materials surrounding the core region, wherein the refractive indices of the high-index and low-index materials are n1 and n2, respectively, the thicknesses of the high-index and low-index layers are h1 and h2, respectively, and n1 > n2 > n0, wherein the refractive indices and thicknesses are selected so as to satisfy, .omega.h, > .omega.l, where .omega.h and .omega.l are two predetermined frequencies given by the respective expressions:
to provide a range of frequencies between the predetermined frequencies .omega.l to .omega.h for which the alternating layers provide omnidirectional reflectivity for electromagnetic radiation incident on the alternating layers from the inner core region, and wherein the number of alternating layers are sufficient to cause omnidirectional reflectivity to be greater than 95% electromagnetic radiation incident on the alternating layers from the inner core region at all angles ranging from 0° to 80° and all polarizations for all frequencies in the omindirectional range of frequencies between .omega.1 to .omega.h.
a dielectric inner core region in which the electromagnetic radiation is to be confined, the inner core region having a refractive index n0, an outer dielectric region surrounding the inner core region to confine the electromagnetic radiation within the inner core region, the outer dielectric region including a plurality of alternating layers of high-index and low-index dielectric materials surrounding the core region, wherein the refractive indices of the high-index and low-index materials are n1 and n2, respectively, the thicknesses of the high-index and low-index layers are h1 and h2, respectively, and n1 > n2 > n0, wherein the refractive indices and thicknesses are selected so as to satisfy, .omega.h, > .omega.l, where .omega.h and .omega.l are two predetermined frequencies given by the respective expressions:
to provide a range of frequencies between the predetermined frequencies .omega.l to .omega.h for which the alternating layers provide omnidirectional reflectivity for electromagnetic radiation incident on the alternating layers from the inner core region, and wherein the number of alternating layers are sufficient to cause omnidirectional reflectivity to be greater than 95% electromagnetic radiation incident on the alternating layers from the inner core region at all angles ranging from 0° to 80° and all polarizations for all frequencies in the omindirectional range of frequencies between .omega.1 to .omega.h.
25. The device of claim 24, wherein the frequency range to midrange ratio is greater than or equal to 20%.
26. The device of claim 24, wherein the frequency range to midrange ratio is greater than or equal to 30%.
27. The device of claim 24, wherein the frequency range to midrange ratio is greater than or equal to 40%.
28. The device of claim 24, wherein said inner core region comprises a gas.
29. The device of claim 28, wherein said inner core region comprises air.
30. The device of claim 24, wherein said low dielectric material comprises a polymer or a glass.
31. The device of claim 30, wherein said high dielectric material comprises germanium or tellurium.
32. The device of claim 24, wherein said inner core region has dimensions on the order of the wavelength of the electromagnetic radiation in the omnidirectional range of frequencies.
33. The device of claim 24, wherein said inner core region has dimensions larger than the wavelength of the electromagnetic radiation in the omnidirectional range of frequencies.
34. The device of any one of claims 24 to 33, wherein the inner core region extends along a waveguide longitudinal axis and the alternating layers surround the inner core region about the waveguide axis to guide the electromagnetic radiation along the waveguide axis.
35. The device of claim 34, wherein said device comprises a circular cross section with respect to the waveguide axis.
36. The device of claim 34, wherein said device comprises a rectangular cross section with respect to the waveguide axis.
37. The device of claim 34, wherein said device comprises a triangular cross section with respect to the waveguide axis.
38. The device of claim 34, wherein said device comprises a hexagonal cross section with respect to the waveguide axis.
39. The device of claim 34, wherein said device is utilized to guide high power electomagnetic radiation.
40. The device of claim 34, wherein said device is utilized to guide high power electromagnetic radiation around bends.
41. The device of claim 34, wherein said device is utilized to guide electromagnetic radiation in an additional range of plurality of broadband regions.
42. The device of any one of claims 24 to 33, wherein the device is utilized as a microcavity to confine electromagnetic radiation.
Applications Claiming Priority (3)
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| US60/104,153 | 1998-10-14 | ||
| PCT/US1999/023833 WO2000022466A1 (en) | 1998-10-14 | 1999-10-14 | Omnidirectional multilayer device for optical waveguiding |
Publications (2)
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| CA2346733A1 CA2346733A1 (en) | 2000-04-20 |
| CA2346733C true CA2346733C (en) | 2007-01-02 |
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| CA002346733A Expired - Lifetime CA2346733C (en) | 1998-10-14 | 1999-10-14 | Omnidirectional reflective multilayer device for confining electromagnetic radiation |
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| US (2) | US6463200B2 (en) |
| EP (1) | EP1121614B1 (en) |
| JP (1) | JP3643774B2 (en) |
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Families Citing this family (82)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP3654836B2 (en) | 1998-02-19 | 2005-06-02 | マサチューセッツ インスティテュート オブ テクノロジー | Photonic crystal omnidirectional reflector |
| DE69926774T2 (en) | 1998-10-14 | 2006-06-01 | Massachusetts Institute Of Technology, Cambridge | DEVICE WITH MULTILAYER FOR DETERMINING ELECTROMAGNETIC RADIATION REFLECTING IN ANY DIRECTION |
| GB9907655D0 (en) * | 1999-04-01 | 1999-05-26 | Secr Defence | A photonic crystal fibre and a method for its production |
| US6606440B2 (en) * | 2000-05-15 | 2003-08-12 | Sumitomo Electric Industries, Ltd. | Microstructured optical fiber |
| US6909729B2 (en) * | 2000-10-26 | 2005-06-21 | Massachusetts Institute Of Technology | Dielectric waveguide with transverse index variation that support a zero group velocity mode at a non-zero longitudinal wavevector |
| EP1366383A1 (en) | 2001-01-25 | 2003-12-03 | Omniguide Communications Inc. | Photonic crystal optical waveguides having tailored dispersion profiles |
| AU2002240145B2 (en) * | 2001-01-25 | 2006-06-29 | Omniguide, Inc. | Low-loss photonic crystal waveguide having large core radius |
| JP2004521379A (en) | 2001-01-31 | 2004-07-15 | オムニガイド コミュニケーションズ インコーポレイテッド | Electromagnetic mode conversion of photonic crystal multimode waveguide |
| US6624945B2 (en) * | 2001-02-12 | 2003-09-23 | Massachusetts Institute Of Technology | Thin film filters using omnidirectional reflectors |
| WO2002084345A1 (en) | 2001-04-12 | 2002-10-24 | Omniguide Communications | High index-contrast fiber waveguides and applications |
| US7272285B2 (en) | 2001-07-16 | 2007-09-18 | Massachusetts Institute Of Technology | Fiber waveguides and methods of making the same |
| CN1559012A (en) | 2001-07-16 | 2004-12-29 | ��ʡ��ѧԺ | Method of forming reflecting dielectric mirrors |
| EP1436652A2 (en) | 2001-10-19 | 2004-07-14 | NKT Research & Innovation A/S | Integrated photonic crystal structure and method of producing same |
| AUPR858401A0 (en) * | 2001-10-30 | 2001-11-29 | University Of Sydney, The | A methodof designing a waveguide |
| JP2005515422A (en) * | 2002-01-19 | 2005-05-26 | アジレント・テクノロジーズ・インク | Gas-filled optical fiber for wavelength calibration or measurement |
| US20040041742A1 (en) * | 2002-01-22 | 2004-03-04 | Yoel Fink | Low-loss IR dielectric material system for broadband multiple-range omnidirectional reflectivity |
| US20040061863A1 (en) * | 2002-08-20 | 2004-04-01 | Digonnet Michel J.F. | Fiber optic sensors with reduced noise |
| US7738109B2 (en) * | 2002-08-20 | 2010-06-15 | The Board Of Trustees Of The Leland Stanford Junior University | Fiber optic sensor using a Bragg fiber |
| EP1567893A4 (en) * | 2002-11-22 | 2007-09-19 | Omniguide Inc | Dielectric waveguide and method of making the same |
| US7321712B2 (en) | 2002-12-20 | 2008-01-22 | Crystal Fibre A/S | Optical waveguide |
| US7346249B2 (en) | 2003-03-21 | 2008-03-18 | Crystal Fibre A/S | Photonic bandgap optical waveguide with anti-resonant core boundary |
| US7361171B2 (en) | 2003-05-20 | 2008-04-22 | Raydiance, Inc. | Man-portable optical ablation system |
| GB2403816A (en) * | 2003-07-11 | 2005-01-12 | Fujitsu Ltd | Optical device with radial discontinuities in the refractive index |
| US7023533B2 (en) | 2003-08-01 | 2006-04-04 | Lucent Technologies Inc. | System and method for determining propagation characteristics of photonic structures |
| US8921733B2 (en) | 2003-08-11 | 2014-12-30 | Raydiance, Inc. | Methods and systems for trimming circuits |
| US20050065502A1 (en) * | 2003-08-11 | 2005-03-24 | Richard Stoltz | Enabling or blocking the emission of an ablation beam based on color of target |
| US8173929B1 (en) | 2003-08-11 | 2012-05-08 | Raydiance, Inc. | Methods and systems for trimming circuits |
| US9022037B2 (en) | 2003-08-11 | 2015-05-05 | Raydiance, Inc. | Laser ablation method and apparatus having a feedback loop and control unit |
| KR100543708B1 (en) * | 2003-12-17 | 2006-01-20 | 삼성전자주식회사 | Mode converter device using omnidirectional reflectors |
| US7167622B2 (en) | 2004-04-08 | 2007-01-23 | Omniguide, Inc. | Photonic crystal fibers and medical systems including photonic crystal fibers |
| US7310466B2 (en) * | 2004-04-08 | 2007-12-18 | Omniguide, Inc. | Photonic crystal waveguides and systems using such waveguides |
| US7331954B2 (en) * | 2004-04-08 | 2008-02-19 | Omniguide, Inc. | Photonic crystal fibers and medical systems including photonic crystal fibers |
| US7349589B2 (en) | 2004-04-08 | 2008-03-25 | Omniguide, Inc. | Photonic crystal fibers and medical systems including photonic crystal fibers |
| US7231122B2 (en) | 2004-04-08 | 2007-06-12 | Omniguide, Inc. | Photonic crystal waveguides and systems using such waveguides |
| US7333705B2 (en) | 2004-12-03 | 2008-02-19 | Searete Llc | Photonic crystal energy converter |
| US7787734B2 (en) * | 2004-12-03 | 2010-08-31 | The Invention Science Fund I, Llc | Photonic crystal energy converter |
| US7499619B2 (en) * | 2004-12-03 | 2009-03-03 | Searete | Photonic crystal energy converter |
| CN100360961C (en) * | 2004-12-31 | 2008-01-09 | 燕山大学 | Omnidirectional image reflector |
| US20070147752A1 (en) * | 2005-06-10 | 2007-06-28 | Omniguide, Inc. | Photonic crystal fibers and systems using photonic crystal fibers |
| US7450808B2 (en) * | 2005-07-08 | 2008-11-11 | Nuffern | Optical fiber article and methods of making |
| US8135050B1 (en) | 2005-07-19 | 2012-03-13 | Raydiance, Inc. | Automated polarization correction |
| US7239786B2 (en) * | 2005-09-13 | 2007-07-03 | National Central University | Hollow optical waveguide by omni-directional reflectors |
| US7099533B1 (en) | 2005-11-08 | 2006-08-29 | Chenard Francois | Fiber optic infrared laser beam delivery system |
| US8232687B2 (en) | 2006-04-26 | 2012-07-31 | Raydiance, Inc. | Intelligent laser interlock system |
| US8189971B1 (en) | 2006-01-23 | 2012-05-29 | Raydiance, Inc. | Dispersion compensation in a chirped pulse amplification system |
| US7444049B1 (en) | 2006-01-23 | 2008-10-28 | Raydiance, Inc. | Pulse stretcher and compressor including a multi-pass Bragg grating |
| US7529454B2 (en) * | 2006-03-17 | 2009-05-05 | Searete Llc | Photonic crystal surface states |
| US7529456B2 (en) * | 2006-03-17 | 2009-05-05 | Searete Llc | Photonic crystal surface states |
| US20090196561A1 (en) * | 2006-03-17 | 2009-08-06 | Searete Llc, A Limited Liability Corporation Of The State Of Delaware | Photonic crystal surface states |
| US7822347B1 (en) | 2006-03-28 | 2010-10-26 | Raydiance, Inc. | Active tuning of temporal dispersion in an ultrashort pulse laser system |
| WO2008003071A2 (en) * | 2006-06-29 | 2008-01-03 | The Board Of Trustees Of The Leland Stanford Junior University | Fiber optic sensor using a bragg fiber |
| US20080177257A1 (en) * | 2007-01-23 | 2008-07-24 | Smith Ronald T | Thermally robust illumination probe tip |
| CN101861655A (en) * | 2007-06-18 | 2010-10-13 | 益科博能源设备（三亚）有限公司 | Methods and apparatuses for waveguiding luminescence generated in a scattering medium |
| US9612369B2 (en) | 2007-08-12 | 2017-04-04 | Toyota Motor Engineering & Manufacturing North America, Inc. | Red omnidirectional structural color made from metal and dielectric layers |
| US9739917B2 (en) | 2007-08-12 | 2017-08-22 | Toyota Motor Engineering & Manufacturing North America, Inc. | Red omnidirectional structural color made from metal and dielectric layers |
| US10870740B2 (en) | 2007-08-12 | 2020-12-22 | Toyota Jidosha Kabushiki Kaisha | Non-color shifting multilayer structures and protective coatings thereon |
| US9229140B2 (en) | 2007-08-12 | 2016-01-05 | Toyota Motor Engineering & Manufacturing North America, Inc. | Omnidirectional UV-IR reflector |
| US9063291B2 (en) | 2007-08-12 | 2015-06-23 | Toyota Motor Engineering & Manufacturing North America, Inc. | Omnidirectional reflector |
| US10048415B2 (en) | 2007-08-12 | 2018-08-14 | Toyota Motor Engineering & Manufacturing North America, Inc. | Non-dichroic omnidirectional structural color |
| US8323391B2 (en) | 2007-08-12 | 2012-12-04 | Toyota Motor Engineering & Manufacturing North America, Inc. | Omnidirectional structural color paint |
| US10788608B2 (en) | 2007-08-12 | 2020-09-29 | Toyota Jidosha Kabushiki Kaisha | Non-color shifting multilayer structures |
| US10690823B2 (en) | 2007-08-12 | 2020-06-23 | Toyota Motor Corporation | Omnidirectional structural color made from metal and dielectric layers |
| CN101803275B (en) * | 2007-10-31 | 2012-07-25 | 朗讯科技公司 | Method for generating a real time billing information in a packet switching based network and network element |
| US20090284983A1 (en) * | 2008-05-16 | 2009-11-19 | Bart Levine | Intrinsically-safe system for mineshaft illumination |
| US8125704B2 (en) | 2008-08-18 | 2012-02-28 | Raydiance, Inc. | Systems and methods for controlling a pulsed laser by combining laser signals |
| WO2011075442A1 (en) | 2009-12-15 | 2011-06-23 | Omniguide, Inc. | Two-part surgical waveguide |
| US8200854B2 (en) * | 2010-08-05 | 2012-06-12 | Verizon Patent And Licensing Inc. | Smart card driven device configuration changes |
| US8554037B2 (en) | 2010-09-30 | 2013-10-08 | Raydiance, Inc. | Hybrid waveguide device in powerful laser systems |
| CN102522299A (en) * | 2011-12-28 | 2012-06-27 | 东南大学 | Electromagnetic band gap structure, electromagnetic band gap high-impedance substrate and planar travelling wave tube |
| US9664832B2 (en) | 2012-08-10 | 2017-05-30 | Toyota Motor Engineering & Manufacturing North America, Inc. | Omnidirectional high chroma red structural color with combination semiconductor absorber and dielectric absorber layers |
| US9678260B2 (en) | 2012-08-10 | 2017-06-13 | Toyota Motor Engineering & Manufacturing North America, Inc. | Omnidirectional high chroma red structural color with semiconductor absorber layer |
| US9658375B2 (en) | 2012-08-10 | 2017-05-23 | Toyota Motor Engineering & Manufacturing North America, Inc. | Omnidirectional high chroma red structural color with combination metal absorber and dielectric absorber layers |
| US10492876B2 (en) | 2012-09-17 | 2019-12-03 | Omniguide, Inc. | Devices and methods for laser surgery |
| US9980775B2 (en) | 2013-03-15 | 2018-05-29 | Omniguide, Inc. | Waveguide locks and counterbalances for waveguide conduits |
| WO2015153043A1 (en) | 2014-04-01 | 2015-10-08 | Toyota Motor Engineering & Manufacturing North America, Inc. | Non-color shifting multilayer structures |
| WO2016044640A1 (en) | 2014-09-18 | 2016-03-24 | Omniguide, Inc. | Laparoscopic handpiece for waveguides |
| US9212912B1 (en) | 2014-10-24 | 2015-12-15 | Honeywell International Inc. | Ring laser gyroscope on a chip with doppler-broadened gain medium |
| US9810824B2 (en) | 2015-01-28 | 2017-11-07 | Toyota Motor Engineering & Manufacturing North America, Inc. | Omnidirectional high chroma red structural colors |
| US20160299291A1 (en) * | 2015-04-13 | 2016-10-13 | Ziva Corporation | Plasmonic waveguides and waveguiding methods |
| EP3245971A1 (en) | 2016-05-16 | 2017-11-22 | Omniguide Inc. | Multi-function handpieces for energy-based surgery |
| US10578797B2 (en) * | 2018-01-24 | 2020-03-03 | Stc.Unm | Hollow core optical fiber with light guiding within a hollow region based on transverse anderson localization of light |
| CN115016052B (en) * | 2022-06-29 | 2023-07-28 | 华中科技大学 | Laser omnidirectional reflecting film and application thereof in wearable laser protection field |
Family Cites Families (36)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE3271976D1 (en) | 1981-03-06 | 1986-08-21 | Hitachi Ltd | Infrared optical fiber |
| US4688893A (en) * | 1985-03-18 | 1987-08-25 | Laakmann Electro-Optics, Inc. | Hollow waveguide having plural layer dielectric |
| IL81287A0 (en) | 1986-01-18 | 1987-08-31 | Sumitomo Electric Industries | High power optical fiber |
| US4852968A (en) | 1986-08-08 | 1989-08-01 | American Telephone And Telegraph Company, At&T Bell Laboratories | Optical fiber comprising a refractive index trench |
| US5261016A (en) | 1991-09-26 | 1993-11-09 | At&T Bell Laboratories | Chromatic dispersion compensated optical fiber communication system |
| US5185827A (en) | 1991-09-26 | 1993-02-09 | At&T Bell Laboratories | Apparatus for compensating chromatic dispersion in optical fibers |
| US5333090A (en) * | 1992-10-13 | 1994-07-26 | Coherent, Inc. | Optical coating for reflecting visible and longer wavelength radiation having grazing incidence angle |
| US5448674A (en) | 1992-11-18 | 1995-09-05 | At&T Corp. | Article comprising a dispersion-compensating optical waveguide |
| DE69430361D1 (en) | 1993-01-08 | 2002-05-16 | Massachusetts Inst Technology | LOW-LOSS OPTICAL AND OPTOELECTRONIC INTEGRATED CIRCUITS |
| US5814367A (en) | 1993-08-13 | 1998-09-29 | General Atomics | Broadband infrared and signature control materials and methods of producing the same |
| US5882774A (en) | 1993-12-21 | 1999-03-16 | Minnesota Mining And Manufacturing Company | Optical film |
| US6101032A (en) * | 1994-04-06 | 2000-08-08 | 3M Innovative Properties Company | Light fixture having a multilayer polymeric film |
| GB2288469B (en) * | 1994-04-15 | 1997-10-22 | Hitachi Cable | Optical hollow waveguide, method for fabricating the same, and laser transmission apparatus using the same |
| US5894537A (en) | 1996-01-11 | 1999-04-13 | Corning Incorporated | Dispersion managed optical waveguide |
| AU693329B2 (en) | 1995-04-13 | 1998-06-25 | Corning Incorporated | Dispersion managed optical waveguide |
| US6080467A (en) | 1995-06-26 | 2000-06-27 | 3M Innovative Properties Company | High efficiency optical devices |
| US5641956A (en) | 1996-02-02 | 1997-06-24 | F&S, Inc. | Optical waveguide sensor arrangement having guided modes-non guided modes grating coupler |
| US5661839A (en) | 1996-03-22 | 1997-08-26 | The University Of British Columbia | Light guide employing multilayer optical film |
| US5999679A (en) | 1997-07-14 | 1999-12-07 | Corning Incorporated | Dispersion compensating single mode waveguide |
| JP3299477B2 (en) | 1997-02-07 | 2002-07-08 | 光信 宮城 | Manufacturing method of hollow waveguide |
| GB9713422D0 (en) | 1997-06-26 | 1997-08-27 | Secr Defence | Single mode optical fibre |
| US6043914A (en) | 1998-06-29 | 2000-03-28 | Mci Communications Corporation | Dense WDM in the 1310 nm band |
| US20010008693A1 (en) | 1998-03-16 | 2001-07-19 | Yoel Fink | Polymer-inorganic multilayer dielectric film |
| US6339665B1 (en) | 1998-03-26 | 2002-01-15 | Lasercomm Inc. | Apparatus and method for compensation of chromatic dispersion in optical fibers |
| US6404952B1 (en) | 1998-03-26 | 2002-06-11 | Lasercomm Inc. | Optical communication system with chromatic dispersion compensation |
| JP3456143B2 (en) | 1998-05-01 | 2003-10-14 | 信越半導体株式会社 | Laminated materials and optical functional devices |
| US6404966B1 (en) | 1998-05-07 | 2002-06-11 | Nippon Telegraph And Telephone Corporation | Optical fiber |
| JP3072842B2 (en) | 1998-05-07 | 2000-08-07 | 日本電信電話株式会社 | Single mode optical fiber |
| US6222673B1 (en) | 1998-08-18 | 2001-04-24 | Coherent, Inc. | Group-delay-dispersive multilayer-mirror structures and method for designing same |
| US6175671B1 (en) | 1998-10-01 | 2001-01-16 | Nortel Networks Limited | Photonic crystal waveguide arrays |
| DE69926774T2 (en) | 1998-10-14 | 2006-06-01 | Massachusetts Institute Of Technology, Cambridge | DEVICE WITH MULTILAYER FOR DETERMINING ELECTROMAGNETIC RADIATION REFLECTING IN ANY DIRECTION |
| US6389197B1 (en) | 1999-02-10 | 2002-05-14 | California Institute Of Technology | Coupling system to a microsphere cavity |
| WO2000051268A1 (en) | 1999-02-23 | 2000-08-31 | Lasercomm, Inc. | High order spatial mode transmission system |
| US6301421B1 (en) | 1999-05-27 | 2001-10-09 | Trw Inc. | Photonic crystal fiber lasers and amplifiers for high power |
| US6434311B1 (en) | 1999-06-10 | 2002-08-13 | Lasercomm Inc. | Reducing mode interference in transmission of a high order mode in optical fibers |
| JP3200629B2 (en) | 1999-08-11 | 2001-08-20 | 独立行政法人通信総合研究所 | Optical modulator using photonic bandgap structure and optical modulation method |
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- 1999-10-14 WO PCT/US1999/023833 patent/WO2000022466A1/en active IP Right Grant
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- 1999-10-14 US US09/418,344 patent/US6463200B2/en not_active Expired - Lifetime
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2002
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| US20020025130A1 (en) | 2002-02-28 |
| US6603911B2 (en) | 2003-08-05 |
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| JP2002527788A (en) | 2002-08-27 |
| EP1121614B1 (en) | 2005-08-17 |
| CA2346733A1 (en) | 2000-04-20 |
| US20020191929A1 (en) | 2002-12-19 |
| US6463200B2 (en) | 2002-10-08 |
| JP3643774B2 (en) | 2005-04-27 |
| WO2000022466A1 (en) | 2000-04-20 |
| DE69926774D1 (en) | 2005-09-22 |
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