WO2005091447A1

WO2005091447A1 - Laser equipment

Info

Publication number: WO2005091447A1
Application number: PCT/JP2005/005176
Authority: WO
Inventors: Masaki Tsunekane; Takunori Taira
Original assignee: Japan Science And Technology Agency
Priority date: 2004-03-24
Filing date: 2005-03-23
Publication date: 2005-09-29
Also published as: JPWO2005091447A1

Abstract

Laser equipment wherein a light guide can be easily constituted for a core having a discretionary shape or a plurality of cores by using a translucent ceramic material for the light guide that guides waves of excitation light on an outer circumference of the core. The laser equipment is provided with a core (4) which includes a laser oscillation element at the center and a light guide (5), which is integrally formed on a circumference of the core (4) and is transparent to excitation light. The laser equipment performs laser oscillation by introducing the excitation light from an external side of the light guide (5) of a solid-state laser crystal fixed to a heat sink on one plane, and by exciting a region of the core (4). The light guide (5) or the light guide (5) and the core (4) are made of a translucent ceramics.

Description

Specification

Laser equipment

Technical field

The present invention relates to a solid-state laser medium and a solid-state laser device equipped with the same.

Background art

[0002] As a conventional solid-state laser medium and solid-state laser device, a core made of a solid-state laser crystal containing a lasing element is provided in the center of the laser medium, and a transparent material for guiding excitation light around the core is provided. A thin crystal with a thickness of lmm or less having a light guide is arranged, and the surface of this crystal opposite to the surface from which laser light is emitted is fixed to a heat sink and has a structure that is cooled (see below). Patent document 1, Non-patent document 1, 2).

[0003] In these conventional examples, the core is circular or square, and the same base material containing no laser oscillation element is used for the light guide.

Patent document 1: U.S. Pat.No. 6,625,193

Patent Document 2: Japanese Patent Application Laid-Open No. 2003-258350

Non-Patent Document 1: Optake's Letters, Vol. 27 (published in 2002), p. 1791

Non-Patent Document 2: Applied 'Physics' Letters, Vol. 83 (issued in 2003), p. 4086 Disclosure of the Invention

[0004] In the above-described conventional technology, as a method of joining and integrating the solid-state laser crystal of the core and the surrounding light guide so that light does not leak, a method using a transparent adhesive or a method using no adhesive is used. Used a technique called optical contact or diffusion bonding, in which the surfaces to be joined were polished with high precision, and after joining the surfaces, they were integrated by applying pressure and heat. However, when an adhesive is used, there are reliability problems such as low mechanical strength of the adhesive, aging, energy loss due to light absorption, and heat generation. In addition, when integrating crystals together outside the optical contour or by diffusion bonding, it is technically difficult to completely integrate the curved surfaces with the curved surfaces due to processing accuracy. Was like that. For this reason, a core that is originally desirably circular Even in this case, a polygonal shape was used as a substitute.

[0005] In addition, when integrating crystals, it is necessary to polish the surface to be joined with high precision, and furthermore, since integration requires extremely high temperature and time, it takes days to manufacture. However, there was a disadvantage that the cost was extremely high. Furthermore, when multiple cores are to be integrally formed in a laser medium to enhance the functionality of a laser device, the above-described method further complicates the manufacturing process, and requires longer manufacturing days and higher costs. In some cases, it was technically difficult to manufacture.

[0006] In view of the above situation, the present invention uses a translucent ceramic material for a light guide that guides excitation light on the outer periphery of a core, and forms a boundary between a core having an arbitrary shape or a plurality of cores at a boundary surface. It is an object of the present invention to provide a solid-state laser medium that can easily and inexpensively produce a light guide with low light loss and high mechanical strength, and a compact high-performance solid-state laser device equipped with the medium.

[0007] In order to achieve the above object, the present invention provides:

[1] In a solid-state laser medium, a core containing a lasing element is provided at the center, and a transparent light guide for excitation light absorbed by the core is integrated around this core, and the core is exposed. Is a solid-state laser medium fixed to a heat sink, the light guide or the light guide and the core are made of translucent ceramic, and one or more cores are provided in the same light guide. It is characterized by.

[2] In the solid-state laser medium according to the above [1], the content of the laser oscillation element in each core or the type of the element is different.

[3] The solid-state laser medium according to the above [1], wherein the core has an elliptical cylindrical shape.

[4] The solid-state laser medium according to the above [1], wherein the core has a concentric cylindrical shape including a plurality of regions, and the content of the laser oscillation element in each of the cores is different.

[5] In the solid-state laser medium according to the above [1], the plurality of cores are arranged at equal intervals.

[6] In the solid-state laser device provided with the solid-state laser medium according to the above [1], The plurality of cores are arranged on the same optical path of the laser light through a surface that is not fixed to the heat sink by a mirror provided on the heat sink.

[7] In the solid-state laser device provided with the solid-state laser medium according to the above [1], a waveguide through which laser-oscillated light passes through is provided near the surface of the solid-state laser medium that is not fixed to the heat sink. An optical block is arranged, a total reflection film for laser light is provided on an outer surface of the light guide block, and the plurality of cores are arranged in the same optical path of the laser light in this block via the total reflection film. It is characterized by.

[8] In the solid-state laser device provided with the solid-state laser medium according to [1], an output mirror is provided independently for each of the plurality of cores.

[9] In the solid-state laser device provided with the solid-state laser medium according to the above [1], the excitation lights emitted from the semiconductor laser bars arranged in a stacked manner are each in a fast axis direction by a microphone aperture lens. After the light is collimated, the semiconductor laser and the lens are arranged so that the light is condensed on the incident window on the side surface of the light guide by a single condenser lens.

Brief Description of Drawings

FIG. 1 is a plan view of a solid-state laser medium showing a first embodiment of the present invention.

FIG. 2 is a sectional view taken along line AA of a solid-state laser device (laser resonator) including the solid-state laser medium shown in FIG.

FIG. 3 is a plan view of a solid-state laser medium according to a second embodiment of the present invention.

FIG. 4 is a sectional view of the solid-state laser medium shown in FIG. 3, taken along line BB.

FIG. 5 is a view showing a Yb concentration distribution of a core part shown in FIG. 3.

6 is a diagram showing an excitation light absorption energy density distribution of a core part shown in FIG. 3.

FIG. 7 is a plan view of a solid-state laser medium according to a third embodiment of the present invention.

[FIG. 8] A solid-state laser device (laser resonator) equipped with the solid-state laser medium shown in FIG. 7

It is a C-C line sectional view.

FIG. 9 is a sectional view of a solid-state laser device (laser resonator) showing a fourth embodiment of the present invention.

FIG. 10 is a sectional view of a solid-state laser device (laser resonator) showing a fifth embodiment of the present invention. is there.

FIG. 11 is a plan view of a solid-state laser medium according to a sixth embodiment of the present invention.

FIG. 12 is a sectional view of a solid-state laser device according to a seventh embodiment of the present invention.

BEST MODE FOR CARRYING OUT THE INVENTION

[0017] In the solid-state laser medium, a core containing a lasing element is provided at the center, a transparent light guide for excitation light absorbed by the core is integrated around the core, and one of the cores is exposed. The surface is a solid-state laser medium fixed to a heat sink, and the light guide or the light guide and the core are made of translucent ceramic.

[0018] Therefore, a light guide can be easily configured for a core having an arbitrary shape or a plurality of cores.

Hereinafter, embodiments of the present invention will be described in detail.

Example

FIG. 1 is a plan view of a solid-state laser medium showing a first embodiment of the present invention, and FIG. 2 is a cross-sectional view taken along line AA of a solid-state laser device (laser resonator) provided with the solid-state laser medium shown in FIG. It is.

In these figures, 1 is a heat sink, 2 is a high heat conductive adhesive layer provided on the heat sink 1, 3 is a total reflection film provided on the high heat conductive adhesive layer 2, and 4 is a laser oscillation element. A cylindrical core made of a solid-state laser material containing: 5, a light guide made of a transparent ceramic that is transparent to the light that excites the core, and 6 and 7 from the short axis direction of the elliptical cylindrical core 4. Excitation light that enters the core through the inside of the light guide 5, 8 is a total reflection mirror, 9 is a laser single oscillation light, 10 is an output mirror, and 11 is an output beam (circular).

A light guide 5 made of a translucent ceramic material is formed around the elliptical cylindrical core 4 in close contact with the core by a sintering method. An example of a method for forming a translucent ceramic by a sintering method is described in Patent Document 2 described above. Excitation lights 6 and 7 enter the light guide 5 from the outer periphery of the light guide 5, reach the core 4 through the light guide 5, are absorbed therein, and are converted into laser oscillation light. Further, heat generated simultaneously with laser oscillation in the core 4 is immediately diffused and absorbed by the heat sink 1 through the adhesive layer 2 having high thermal conductivity, so that the core 4 is effectively cooled and stable laser oscillation becomes possible. . For example, the length of the major axis of the elliptical cylindrical core 4 is 8 mm, and the length of its minor axis is 3 mm. The thickness of the light-transmitting ceramic 5 as the light guide and the thickness of the elliptical cylindrical core 4 are 0.3 mm. As shown in this figure, the excitation light beams 6 and 7 are made to enter the elliptic cylindrical core 4 in the short axis direction, thereby narrowing the excitation light in the horizontal direction as compared with the case where the excitation light is incident from the long axis direction. Therefore, the light can be absorbed in the elliptical cylindrical core 4 with a simple condensing optical system.

The material of the elliptic cylindrical core 4 is, for example, YAG (yttrium aluminum garnet) containing Yb (ytterbium) as a laser oscillation element, and a light guide (translucent ceramic) 5 as a material of a laser. A typical example is a YAG that does not contain an oscillating element, but other oscillating elements may be Nd (neodymium) or transition metals such as Tm (thulium) and Ho (holmium). Further, Cr (chromium) or Ti (titanium) may be used, or a plurality of them may be included. As a base material for the core 4 and the light guide 5, in addition to YAG, YVO (yttrium vanadate)

Four

, GdVO (gadolium vanadate), YLF (yttrium 'lithium.fluoride), GGG (gad

Four

Lium 'gallium' garnet) may be used. Excitation lights 6 and 7 have wavelengths that are absorbed by the laser oscillation element. For example, a core 4 using Yb: YAG is suitable for a 940 nm or 970 nm force. As described above, the wavelengths of the excitation lights 6 and 7 are selected according to the material of the core 4 to be used.

[0025] Also, the base materials of the core 4 and the light guide 5 may be different, but the same material has a closer refractive index, so that light loss at the boundary can be suppressed. In addition, when the core 4 and the light guide 5 are integrated during the manufacturing process, the handling is easier, and the power S can be reduced to suppress light loss at the boundary.

Further, the light guide 5 may be made of a translucent ceramic, and the power core 4 may be made of a crystal, and may be a translucent ceramic containing a laser-oscillating element.

[0027] The high thermal conductive adhesive layer 2 may be an organic or inorganic adhesive, or may be Au, Ag, Sn, Sb, In.

A metal solder material containing Pb, Zn, Cu, etc. may be used.

[0028] The heat sink 1 includes metal materials such as Cu and CuW, as well as diamond, SiC, A1N, and Be.

Nonmetals such as 0, CBN and DLC, and composite materials may be used.

[0029] As shown in Fig. 2, the laser oscillation light 9 is emitted in the major axis direction of the core 4 with respect to the laser light incident surface of the core 4 to the Brewster angle (Brewster angle). Therefore, if the direction of polarization of light is in the plane of incidence, the mirror position is configured to be incident at a specific angle of incidence at which the reflectance of light at the material surface is zero), so that the laser of core 4 Even if an anti-reflection film is not formed on the surface through which the oscillating light passes, the reflectance becomes zero, and a laser resonator with low loss can be constructed.

FIG. 3 is a plan view of a solid-state laser medium according to a second embodiment of the present invention, and FIG. 4 is a cross-sectional view taken along a line BB of the solid-state laser device including the solid-state laser medium shown in FIG.

[0031] In these figures, 21 is a first cylindrical core, 22 is a second cylindrical core formed around the first cylindrical core 21, and 23 is a second cylindrical core. The light guide (translucent ceramic) formed outside the core 22 of 2, the excitation light 24, 25, 26, 27 is the excitation light that enters the core through the inside of the light guide 23 from four directions around .

In such a double structure, by changing the concentration of the laser-oscillating element in the first cylindrical core 21 and the second cylindrical core 22, the excitation inside the cores 21, 22 is performed. The distribution (excitation light absorption distribution) can be controlled.

For example, as shown in FIG. 5, the cylindrical first core 21 has a Yb concentration of 10 at% and a diameter of 3 mm, and the cylindrical second core 22 has a Yb concentration of 5 at% and a diameter of 3 at%. When the distance is set to 5 mm and the four-directional force excitation of the opposing light guide 23 is performed, the absorption energy density distribution of the excitation light becomes as shown in FIG. 6, indicating that the excitation distribution is relatively flat. As in the past, if the concentration of the laser-oscillating element in the core is uniform, the absorbed energy density decreases exponentially from the periphery of the core to the inside, so it is necessary to obtain a uniform distribution. However, if the laser oscillation element concentration can be increased toward the center of the core as in the present invention, pseudo-uniform excitation distribution can be achieved, and laser emission within the core can be achieved by making the excitation distribution uniform. Dispersion and reduction of distortion due to heat generated by vibration can be achieved, and as a result, laser output and the quality of one laser beam can be improved.

In this embodiment, both the first core and the second core may have a cylindrical outer shape. The elliptical cylindrical shape shown in FIG. 1 or a polygonal column shape may be used. Either or both of the first core and the second core may be made of a translucent ceramic. In particular, by making the second core also a translucent ceramic, an integrated structure can be formed regardless of the outer shape of the first core. Further, if necessary, the third and fourth cores may be provided outside the second core. Ko It is possible to obtain a more uniform absorption distribution in the core by making the concentration of laser elements smaller and making the concentration difference of the laser element smaller.

[0035] In the above-described embodiments of the solid-state laser medium, the example in which the core power is the center of laser oscillation is described. However, a plurality of cores serving as the center of laser oscillation are formed in the same light guide. It ’s been good, it ’s okay.

FIG. 7 is a plan view of a solid-state laser medium showing a third embodiment of the present invention, and FIG. 8 is a cross-sectional view taken along line C-C of the solid-state laser device (laser resonator) provided with the solid-state laser medium shown in FIG. It is.

In these figures, 31 is a first cylindrical core, 32 is a second cylindrical core, 33 is a third cylindrical core, 34 is a fourth cylindrical core, 35 Is a light guide (translucent ceramic) formed outside the cylindrical cores 31-34, 36 is an anti-reflection film, 37 and 38 are excitation lights, 41 is a first total reflection mirror, and 42 is a 2 is a total reflection mirror, 43 is an output mirror, and 44 is one laser output. Other configurations in FIG. 8 are the same as those in FIG.

In this embodiment, a plurality of cylindrical cores 31 to 34 are formed in the same light guide 35 at equal intervals. With such a configuration, it is possible to increase the laser output by a factor of four while maintaining a narrow laser beam without increasing the area of one core, and it is possible to easily increase the brightness of the laser beam. In addition, by providing a plurality of cores in the same light guide 35, it is possible to simultaneously excite a plurality of cores by the excitation light propagating in the light guide 35, compared to a case where each core is individually provided with an optical guide. Thus, the configuration can be simplified, and the laser medium can be reduced in size and cost. In this embodiment, the reflection mirror 42 provided on the outside for reflection reflects the laser light three times with one sheet by utilizing the fact that the cores are at equal intervals. You can use a mirror and reflect it with three mirrors.

In these figures, 51 is a light guide block, 52 and 54 are antireflection films, 53 is a total reflection film, 55 is a total reflection mirror, 56 is an output mirror, and 57 is a laser output. Other configurations are the same as those in FIG. This embodiment also has a configuration having a plurality of cores as shown in the third embodiment. However, instead of the total reflection mirror 42, a light guide block 51 through which laser oscillation light passes is provided with a laser medium. The total reflection film 53 is provided outside the light guide block 51 so that the laser oscillation light is turned back.

With this configuration, since the total reflection film 53 is fixed to the laser crystal, the stability of the laser resonator can be improved and the size can be reduced.

FIG. 10 is a sectional view of a solid-state laser device (laser resonator) showing a fifth embodiment of the present invention.

[0044] In this figure, 61 is a first output mirror, 62 is a second output mirror, 63 is a third output mirror, 64 is a fourth output mirror, 65 is a first laser output, and 66 is a first output mirror. The second laser output, 67 is the third laser output, and 68 is the fourth laser output. Other configurations are the same as those in FIG.

In this embodiment, output mirrors 61-64 are provided independently for a plurality of cores 31-34 so that laser oscillation operation is performed.

With such a configuration, for example, by changing the type of laser medium of each cylindrical core 31-34 and the type of each output mirror 61-64, the output of light of a different wavelength, here, Laser power 65-68 can be obtained. When the laser element or the base material of the cylindrical cores 31 to 34 is changed, it is desirable to change the wavelength of the excitation light to each of the cylindrical cores 31 to 34 to an optimum one. By changing the transmission wavelength of the output mirror 61-64 even with the same excitation wavelength and the same core medium, for example, even with the same Nd: YAG core, oscillation at wavelengths of 946 nm, 1064 nm, 1130 nm, etc. Each core power can be independently and simultaneously. With such a configuration, an integrated multi-wavelength optical function element can be configured.

FIG. 11 is a plan view of a solid-state laser device according to a sixth embodiment of the present invention.

[0048] In this figure, 71 is a cylindrical first core, 72 is a cylindrical second core, 73 is a cylindrical third core, 74 is a cylindrical fourth core, and 75 is a cylindrical core. A fifth core, 76 is a cylindrical sixth core, and 77 is a seventh cylindrical core.

In this embodiment, the number of cores is further increased from the plurality of cores shown in FIG. 7, and the arrangement thereof is made two-dimensional, so that the excitation on the opposite side is possible even for uniform excitation. Light absorption leakage It is configured so that excitation can be efficiently performed without any omission. In this figure,

Numeral 78 is a light guide (translucent ceramic), and 79 and 80 are excitation lights.

In this figure, 81 is a heat sink, 82 is a semiconductor laser bar, 83 is a micro lens, 84 and 85 are condenser lenses, 86 is excitation light, 91 is a heat sink, 92 is a high thermal conductive adhesive layer, and 93 is A total reflection film, 94 is a cylindrical core, 95 is a light guide, 96 is an antireflection film, 97 is an output mirror, and 98 is laser oscillation light.

In this embodiment, the excitation light 86 emitted from the stacked semiconductor laser bars 82 is collimated in the fast axis direction by the microlenses 83, and after passing through the condenser lens 84, The light is condensed by a single condenser lens 85 into the entrance window 95A on the side of the light guide 95. The condenser lens 84 is used to collect the excitation light 86 in the slow axis direction. The excitation light 86 that has entered the light guide 95 propagates through the light guide 95 while repeating total reflection on the upper and lower surfaces of the light guide 95, and reaches the cylindrical core 94. A laser element that absorbs excitation light and stimulates and emits laser light is added to the cylindrical core 94, and a laser resonator is formed between the output mirror 97 and the total reflection film 93, and laser oscillation occurs. . The cylindrical core 94 and the light guide 95 are fixed to the heat sink 91 via the total reflection film 93 and the high thermal conductive adhesive layer 92, and the heat generated when the excitation light is absorbed in the cylindrical core 94. Has the effect of effectively dissipating heat.

[0053] The present invention is not limited to the above-described embodiments, and various modifications are possible based on the spirit of the present invention, and these are not excluded from the scope of the present invention.

According to the present invention, a solid-state laser medium having an arbitrary shape that is optimal for excitation or oscillation is produced by a technology for forming a translucent ceramic, so that a core having an arbitrary shape or a plurality of cores can be irradiated with light. The guide can be easily configured, and high oscillation efficiency and beam quality of the laser can be obtained.

Industrial applicability

With the solid-state laser medium of the present invention and the solid-state laser device provided with the same, the same light guide for transmitting the excitation light to a core having an arbitrary shape or a plurality of cores can be easily formed at a low cost for a short period of time. Laser medium that can be manufactured with A high-performance type laser device can be used as a laser device capable of obtaining high laser output and beam quality.

Claims

The scope of the claims

[1] In a solid-state laser medium, a core containing a lasing element is provided at the center, and a transparent light guide for excitation light absorbed by the core is integrated around the core. A surface is a solid-state laser medium fixed to a heat sink, and the light guide or the light guide and the core are made of translucent ceramic, and have one or more cores in the same light guide. A solid-state laser medium characterized by the above.

2. The solid-state laser medium according to claim 1, wherein the content of the laser oscillation element in each core or the type of the element is different.

[3] The solid-state laser medium according to claim 1, wherein the core has an elliptical cylindrical shape.

4. The solid-state laser medium according to claim 1, wherein the core has a concentric cylindrical shape having a plurality of regional forces, and the content of the laser oscillation element in each of the cores is different.

[5] The solid-state laser medium according to claim 1, wherein the plurality of cores are arranged at equal intervals.

[6] The solid-state laser device provided with the solid-state laser medium according to claim 1, wherein the plurality of cores are arranged in the same optical path of the laser light through a surface not fixed to the heat sink by a mirror provided outside. A solid-state laser device.

[7] The solid-state laser device provided with the solid-state laser medium according to claim 1, wherein a light guide block through which laser oscillation light passes is disposed near a surface of the solid-state laser medium which is not fixed to the heat sink. And a total reflection film for laser light is provided on an outer surface of the light guide block, and the plurality of cores are arranged in an optical path of the same laser light in the block via the total reflection film. And a solid-state laser device.

[8] The solid-state laser device provided with the solid-state laser medium according to claim 1, wherein an output mirror is provided independently for each of the plurality of cores.

[9] In the solid-state laser device provided with the solid-state laser medium according to claim 1, the excitation light emitted from the semiconductor laser bars arranged in a stacked manner is applied to each of the microscopic laser beams. The semiconductor laser and the lens are arranged so that the light is collimated in the fast axis direction by the lens and then condensed on the entrance window on the side surface of the light guide by a single condenser lens. Solid laser device.