CN102790253A - Directional coupler - Google Patents

Directional coupler Download PDF

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CN102790253A
CN102790253A CN2011101281831A CN201110128183A CN102790253A CN 102790253 A CN102790253 A CN 102790253A CN 2011101281831 A CN2011101281831 A CN 2011101281831A CN 201110128183 A CN201110128183 A CN 201110128183A CN 102790253 A CN102790253 A CN 102790253A
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silicon
directional coupler
column
coupling
crystal structure
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CN102790253B (en
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王曦
杨志峰
武爱民
甘甫烷
林旭林
李�浩
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Shanghai Institute of Microsystem and Information Technology of CAS
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Shanghai Institute of Microsystem and Information Technology of CAS
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Abstract

The invention discloses a directional coupler which uses an auto-collimation effect of a two-dimensional rectangular lattice columnar photonic crystal to achieve directional coupling, belonging to the optical technical field of a semiconductor. A certain number of coupling columns of the same dimension are introduced between long sides of two adjacent rows of silicon columns by the directional coupler, so that an auto-collimation light beam broadcasting in one row of columns is coupled to the other row of columns to continuously carry out auto-collimation transmission by the introduced middle columns; the transmission power proportion of the auto-collimation light beams in the two rows of columns can be controlled by controlling the number of the middle columns, so that optical coupling between the two adjacent rows of silicon columns is achieved. Compared with a traditional directional coupler, the photonic crystal directional coupler provided by the invention can control the coupling length of the device to be within 10 microns or shorter, so that the length of the overall device is greatly shortened, and the structure is more compact. Simultaneously, the transmission power proportion of the auto-collimation light beams in the two rows of columns can be controlled by controlling the quantity of the middle columns, thereby flexibly controlling the coupling efficiency.

Description

Directional coupler
Technical field
The present invention relates to a kind of directional coupler that is applied to fields such as optical communication, photometry calculation, light sensing and optical measurement, particularly a kind of photonic crystal directional coupling structure based on the SOI substrate belongs to the semiconductor optical technical field.
Background technology
Traditional directional coupler adopts two parallel fiber waveguides to carry out lateral usually, and is as shown in Figure 1.
According to the light wave coupled wave theory, the coupling between the waveguide need be satisfied coupledwave equation:
da 1 ( z ) dz = - iβ a 1 ( z ) + ia 2 ( z ) K 21
da 2 ( z ) dz = - iβ a 2 ( z ) + i a 1 ( z ) K 12
Wherein, K 21And K 12Be coupling coefficient, a (z) is a coupled wave.Situation for the multimode coupling all has coupling between each pattern, coupling coefficient is corresponding to be increased, and equational number is also corresponding to be increased.
According to coupledwave equation, can obtain the power expression that transmits in two waveguides:
P 1＝|a 1(0)| 2cos 2δz
P 2 = | a 2 ( 0 ) | 2 ( K 12 K 21 ) sin 2 δz
Can find out that by above two formulas the power of propagating in the waveguide changes with transmission range, so; Coupling state and coupling length between two waveguides are closely related, in practical application, for realizing higher coupling efficiency; Usually need long coupling length; Make that the integral device size is bigger, simultaneously, along with the increase of coupling length; Scale error between two parallel optical waveguides reaches the loss of bringing owing to the interface roughness of semiconductor fabrication process introducing, and all the coupling efficiency to directional coupler has produced adverse effect.
Summary of the invention
The technical problem that the present invention will solve is: a kind of directional coupling structure is provided, the size of coupler is dwindled greatly, and can control coupling efficiency flexibly.
For solving the problems of the technologies described above, directional coupler provided by the invention realizes that based on the two-dimentional rectangular lattice column photon crystal structure of SOI substrate this directional coupler comprises: input waveguide, output waveguide, coupling cylinder.Wherein, The long edge lengths b of the rectangular lattice arrangement of column photon crystal structure is at least 4 times of silicon column radius r in the column photonic crystal; Input waveguide and output waveguide are adjacent two row's silicon posts in the rectangular lattice column photonic crystal, and input, outbound course are all along rectangular lattice short side direction; The coupling column body is positioned in the middle of said adjacent two row's silicon posts, and it is aliging with the cylinder of adjacent two row's silicon posts along rectangular lattice long side direction, and with adjacent two arrange the silicon posts distance equate.
Further, the coupling cylinder radius with the height with the column photon crystal structure in the silicon post radius and equate that highly respectively the height of the two is the thickness of SOI substrate top layer silicon.
Further, the ratio beta scope of the long edge lengths b of the rectangular lattice arrangement of column photon crystal structure, bond length a is: 2≤β≤2.5.
Further, the scope of the radius r of coupling cylinder and column photon crystal structure silicon post is: 0.3a≤r≤0.5a.
Further, the scope of the height h of coupling cylinder and column photon crystal structure silicon post is: 1.5a≤h≤3a.
More excellent, the radius r of coupling cylinder is 0.39a, and height h is 2a, and the bond length a of the rectangular lattice arrangement of column photon crystal structure is 400nm, and the ratio beta of long edge lengths b, bond length a is 2.4.
Further, the quantity of coupling cylinder is at least 2, and is more excellent, and the quantity of coupling cylinder is at least 16.
Further, the silicon post of coupling cylinder and column photon crystal structure forms through electron beam exposure, inductively coupled plasma technology etching or FIB etching synchronously.
Technique effect of the present invention is; Utilize the auto-collimation effect of two-dimentional rectangular lattice column photonic crystal; Through in the middle of the long limit of adjacent two row's silicon posts, introducing the coupling cylinder of some, same size; Like this; The middle cylinder that the auto-collimation light beam of in an organ timbering body, propagating is introduced into is coupled to and continues the auto-collimation propagation in another organ timbering body, can control the ratio of auto-collimation beam Propagation power in the two organ timbering bodies through the quantity that controls middle cylinder, thereby realizes the optical coupling of adjacent two row's silicon intercolumniations.With respect to traditional directional coupler, photonic crystal directional coupler provided by the invention can be controlled at 10 μ m with interior even shorter with the device coupling length, and this greatly shortens the length of total device, and structure is more compact.Simultaneously; Can control the ratio of auto-collimation beam Propagation power in the two organ timbering bodies through the quantity of cylinder in the middle of controlling; Can control coupling efficiency flexibly, in addition, the directional coupler based on photon crystal structure provided by the invention is based on the SOI substrate; With present mature C MOS process compatible, preparation technology is simple ripe, with low cost.
Description of drawings
Fig. 1 is traditional directional coupling structure sketch map;
Fig. 2 is the ability zone face of two-dimentional rectangular lattice column slab photonic crystal different beta value;
Fig. 3 can be with isofrequency map for two-dimentional rectangular lattice column slab photonic crystal TE pattern second;
Fig. 4 is a directional coupling structure sketch map provided by the invention;
Fig. 5 a-5e is under the different coupling cylinder quantity, directional coupler coupling propagation condition FDTD simulation sketch map provided by the invention;
The directional coupler side schematic view that Fig. 6 provides for invention.
The component symbol mark
Figure BDA0000061866770000031
Embodiment
For making the object of the invention, technical scheme and advantage clearer, the present invention is made further detailed description below in conjunction with accompanying drawing.
In general, through photonic crystal inner introduce defective as passage can lead beam transmission.But photonic crystal also has the character of a uniqueness---auto-collimation effect.Based on this effect, need not introduce any defective in photonic crystal inside, light beam self just can overcome diffraction and disperse collimation and transmit forward.This characteristic comes from the dispersion relation of photonic crystal, and the auto-collimation light beam also have the zero crossing effect except can autocollimation the transmission, and the insensitive effect of angle is to effects such as the photon crystal structure precision are insensitive.
Fig. 2 is the ability zone face of two-dimentional rectangular lattice column slab photonic crystal different beta value.
Compare with the tetragonal periodic structure, rectangular lattice has the more structural parameter owing to symmetry reduces, and this provides more multipath for designing and regulate the Brillouin zone band structure.In order to obtain to obtain smooth as far as possible equifrequent line to the insensitive auto-collimation effect of incident angle.Research shows that β (β is the ratio of long limit of rectangular lattice and minor face) is to the zone face structure having very big influence.As shown in Figure 2, when the fixed cylinder radius is 0.15a, when β gets different numerical value (all the other parameter constants), the symmetrical structure photonic crystal can zone face.Clearly, when β=1, the situation when can zone face being tetragonal; Along with the β increase, can be compressed at reciprocal lattice short side direction (corresponding real space lattice long side direction) by zone face, the ability zone face in centre position, reciprocal lattice two ends swells simultaneously, the ability zone face depression in centre position, both sides; Further increase β, the ability zone face at reciprocal lattice two ends become smooth gradually.When β 2 between 2.5 the time, the reciprocal lattice two ends can have very flat portions by zone face, promptly have very smooth equifrequent line in this case.
Fig. 3 is for being β=2, r=0.4a, and during h=2.05a, the isofrequency map that unsymmetric structure photonic crystal second can be with under the TM pattern.As shown in Figure 3, normalized frequency is that the equifrequent line of 0.29c/a is very smooth.In the case, even incidence angle is 90 °, light beam still can be propagated along rectangular lattice short side direction auto-collimation.
Based on this, as shown in Figure 4, the directional coupling structure that this embodiment provides comprises: input waveguide 110, output waveguide 120, coupling cylinder 201.Wherein, The long edge lengths b of the rectangular lattice arrangement of column photon crystal structure (referring to the distance between the silicon post center of circle) is at least 4 times of silicon column radius r in the column photonic crystal; Input waveguide 110 and output waveguide 120 be adjacent two to arrange the silicon posts in the rectangular lattice column photonic crystal, and input, outbound course are all along rectangular lattice short side direction; Coupling cylinder 201 is positioned in the middle of said adjacent two row's silicon posts, and it align with the cylinder of adjacent two row's silicon posts (i.e. input, output waveguide) along rectangular lattice long side direction, and it is equal to arrange the distance of silicon posts to adjacent two.
In this embodiment, the radius of silicon post and equate that highly respectively the height h of the two is the thickness of SOI substrate top layer silicon in the radius r of coupling cylinder 201 and height h and the column photon crystal structure; The ratio beta scope of the long edge lengths b of the rectangular lattice arrangement of column photon crystal structure, bond length a (distance between the silicon post center of circle) is: 2≤β≤2.5; The scope of the radius r of coupling cylinder 201 and column photon crystal structure silicon post is: 0.3a≤r≤0.5a; The scope of the height h of coupling cylinder 201 and column photon crystal structure silicon post is: 1.5a≤h≤3a.As shown in Figure 6, said SOI substrate comprises substrate silicon layer 101, is positioned at the silicon dioxide buried regions 102 on the substrate silicon layer 101 and is positioned at the top layer silicon 103 on this silicon dioxide buried regions 102.
As preferred forms, the radius r of coupling cylinder 201 is 0.39a, and height h is 2a, and the bond length a of the rectangular lattice arrangement of column photon crystal structure is 400nm, and the ratio beta of long edge lengths b, bond length a is 2.4.
Optional, the quantity of coupling cylinder 201 is at least 2, and as preferred forms, the quantity of coupling cylinder 201 is 16.
Fig. 5 a to Fig. 5 e is for adopting the 3D-FDTD method when introducing the middle cylinder of varying number, the numerical simulation of auto-collimation beam propagation situation.The structural parameters that adopt during numerical simulation are: β=2.4, and r=0.39a, h=2a, a=400nm, propagating light beam is the TM pattern, wavelength is 1500nm.
In the middle of table 1 varying number under the cylinder situation, auto-collimation light beam coupling/penetrate power ratio
Figure BDA0000061866770000041
Table 1 has been listed under the middle cylinder situation of varying number, auto-collimation light beam coupling/penetrate power ratio.The result of numerical experiment shows, adopts this structure can realize the directional couple of auto-collimation light beam; Can well control the coupling of auto-collimation light beam/penetrate power ratio through the quantity of cylinder in the middle of controlling.
In this embodiment, the silicon post of coupling cylinder and column photon crystal structure forms through electron beam exposure, inductively coupled plasma technology etching or FIB etching synchronously.
The directional coupling structure that this embodiment provides utilizes the auto-collimation effect of two-dimentional rectangular lattice column photonic crystal to realize; Through in the middle of the long limit of adjacent two row's silicon posts, introducing the coupling cylinder of some, same size; Like this; The middle cylinder that the auto-collimation light beam of in an organ timbering body, propagating is introduced into is coupled to and continues the auto-collimation propagation in another organ timbering body; Quantity through cylinder in the middle of controlling can control the ratio of auto-collimation beam Propagation power in the two organ timbering bodies, thereby realizes the optical coupling of adjacent two row's silicon intercolumniations.With respect to traditional directional coupler, photonic crystal directional coupler provided by the invention can be controlled at 10 μ m with interior even shorter with the device coupling length, and this greatly shortens the length of total device, and structure is more compact.Simultaneously; Can control the ratio of auto-collimation beam Propagation power in the two organ timbering bodies through the quantity of cylinder in the middle of controlling; Can control coupling efficiency flexibly, in addition, the directional coupler based on photon crystal structure provided by the invention is based on the SOI substrate; With present mature C MOS process compatible, preparation technology is simple ripe, with low cost.
It is understandable that though the present invention with the preferred embodiment disclosure as above, yet the foregoing description is not in order to limit the present invention.For any those of ordinary skill in the art; Do not breaking away under the technical scheme scope situation of the present invention; All the technology contents of above-mentioned announcement capable of using is made many possible changes and modification to technical scheme of the present invention, or is revised as the equivalent embodiment of equivalent variations.Therefore, every content that does not break away from technical scheme of the present invention, all still belongs in the scope of technical scheme protection of the present invention any simple modification, equivalent variations and modification that above embodiment did according to technical spirit of the present invention.

Claims (10)

1. directional coupler is characterized in that: it is included in, and etching forms on the top layer silicon of SOI substrate, and by the column photon crystal structure that is rectangular lattice arrangement that the silicon post is formed, is provided with the cylinder (201) that is coupled between two adjacent row's silicon posts (110,120); Said coupling cylinder aligns with the cylinder of said adjacent two row's silicon posts, and its distance to said adjacent two row's silicon posts equates; The said length b that is the long limit of rectangular lattice arrangement is at least four times of silicon column radius r in the column photon crystal structure, and said two adjacent row's silicon posts are respectively as input waveguide and output waveguide; Said SOI substrate comprises substrate silicon layer (101), is positioned at the silicon dioxide buried regions (102) on the substrate silicon layer (101) and is positioned at the top layer silicon (103) on this silicon dioxide buried regions (102).
2. directional coupler according to claim 1 is characterized in that, the radius of said coupling cylinder (201) with the height with said column photon crystal structure in the silicon post radius and highly equate.
3. directional coupler according to claim 1 is characterized in that, the scope of the ratio beta of the long edge lengths b of rectangular lattice arrangement and bond length a is in the said column photon crystal structure: 2≤β≤2.5.
4. directional coupler according to claim 3 is characterized in that, the span of the radius r of said coupling cylinder is: 0.3a≤r≤0.5a, wherein, a is the bond length a of rectangular lattice arrangement in the column photon crystal structure.
5. directional coupler according to claim 3 is characterized in that, the span of the height h of said coupling cylinder is: 1.5a≤h≤3a, wherein, the long edge lengths b of rectangular lattice arrangement and bond length a in the column photon crystal structure.
6. according to claim 3 or 4 or 5 described directional couplers; It is characterized in that the radius r of said coupling cylinder is 0.39a, height h is 2a; The bond length a of the rectangular lattice arrangement of said column photon crystal structure is 400nm, and the ratio beta of long edge lengths b, bond length a is 2.4.
7. directional coupler according to claim 6 is characterized in that, the quantity of said coupling cylinder is at least 2.
8. directional coupler according to claim 7 is characterized in that, the quantity of said coupling cylinder is 16.
9. directional coupler according to claim 1 is characterized in that, the silicon post of said coupling cylinder and column photon crystal structure forms through electron beam exposure, inductively coupled plasma technology etching or FIB etching synchronously.
10. a directional coupler preparation method is characterized in that, may further comprise the steps:
1) preparation SOI substrate;
2) the column photon crystal structure that is rectangular lattice arrangement that etching forms on the top layer silicon of above-mentioned SOI substrate;
3) in the column photon crystal structure, form coupling cylinder (201) between adjacent two row's silicon posts; Said coupling cylinder aligns with the cylinder of said adjacent two row's silicon posts, and equates with the distance of said adjacent two row's silicon posts; The length b on the long limit of said rectangular lattice arrangement is at least four times of silicon column radius r in the column photonic crystal, and said two adjacent row's silicon posts are respectively as input waveguide and output waveguide.
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Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN108802908A (en) * 2018-05-03 2018-11-13 西北大学 Two-output impulse generator optical switch based on the sublattice of nonlinear optical containing defect

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20010026668A1 (en) * 2000-03-29 2001-10-04 Nec Corporation Photonic crystal waveguide and directional coupler using the same
US20070280592A1 (en) * 2004-03-03 2007-12-06 National Institute Of Advanced Industrial Sci & Tech Photonic Crystal Coupling Defect Waveguide and Photonic Crystal
CN101859004A (en) * 2010-06-29 2010-10-13 南京理工大学 Design method of two-dimensional photonic crystal waveguide coupler

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20010026668A1 (en) * 2000-03-29 2001-10-04 Nec Corporation Photonic crystal waveguide and directional coupler using the same
US20070280592A1 (en) * 2004-03-03 2007-12-06 National Institute Of Advanced Industrial Sci & Tech Photonic Crystal Coupling Defect Waveguide and Photonic Crystal
CN101859004A (en) * 2010-06-29 2010-10-13 南京理工大学 Design method of two-dimensional photonic crystal waveguide coupler

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN108802908A (en) * 2018-05-03 2018-11-13 西北大学 Two-output impulse generator optical switch based on the sublattice of nonlinear optical containing defect
CN108802908B (en) * 2018-05-03 2019-08-06 西北大学 Two-output impulse generator optical switch based on the sublattice of nonlinear optical containing defect

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