JP2016201435A - Laser light source device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a high-output laser light source device.SOLUTION: The laser light source device comprises: a laser medium 5 which has a waveguide structure in a thickness direction of a cross section that is vertical to an optical axis, and generates a gain with respect to laser light; a heat sink 2 that is bonded to one face side of the laser medium via a clad 4; a semiconductor laser 1 which is disposed proximately to one end face of the laser medium and makes excitation light incident to the laser medium; and a nonlinear material 7 which is disposed proximately to the other end face of the laser medium and has a waveguide structure in the same direction as the waveguide structure of the laser medium. The laser medium is oscillated in a spatial mode by lens effects that are effects that a plurality of lenses are arranged side by side in a direction vertical to the optical axis and the thickness direction, in accordance with refractive index distribution within the laser medium. A composition plane of the heat sink to the clad has a comb structures where the teeth of a comb are disposed at fixed intervals within a cross section which is vertical to the optical axis. A comb width of the teeth at both ends of the comb structure and a comb width of the teeth of the comb neighboring to the teeth at both the ends are made narrower than a comb width of the other teeth of the comb.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a laser light source device applied to a high-power laser device used for a light source such as a projector.

Conventionally, in order to realize a laser light source device capable of high-intensity oscillation, a mode control waveguide type laser light source device shown in FIGS. 7 and 8 has been proposed. (For example, refer to Patent Document 1).
FIG. 7 is a side view showing a configuration of a conventional mode control waveguide type laser light source device. FIG. 8 is a cross-sectional view of the section aa ′ in FIG. 7 as seen from the laser emission side.

In FIG. 7, the conventional laser light source device has an excitation semiconductor laser 101 that emits excitation light, a waveguide structure in the thickness direction of a cross section perpendicular to the optical axis 106, and a laser in the optical axis 106 direction. A laser medium 105 that emits light, a clad 104 bonded to the lower surface of the laser medium 105, a heat sink 102 bonded to the lower surface of the clad 104 by a bonding material 103, and a laser beam emitted from the laser medium 105 are incident. And a non-linear material 107 that converts to a second harmonic laser beam by a non-linear effect.
As shown in FIG. 8, the heat sink 102 has a comb structure in which the joint surface of the heat sink 102 with respect to the clad 104 has the same comb width W <b> 1 in a cross section perpendicular to the optical axis 106.

Japanese Patent No. 4392024

  As described above, in the conventional laser light source device, in the comb structure having the same comb width W 1 provided in the heat sink 102, the heat generated in the laser medium 105 is radiated from the comb teeth joined by the joining material 103. Then, by generating a periodic temperature distribution in the waveguide of the laser medium 105, a thermal lens is generated between the comb teeth, and uniform laser oscillation is performed.

  However, as shown in FIG. 9, the temperature distribution diagram in the direction perpendicular to the waveguide thickness direction with respect to the optical axis 106 in the laser medium 105 shows that the amount of heat flowing into the comb structure of the heat sink 102 is at both ends of the laser medium 105. Since it is relatively small, the laser medium temperature is lower than the central part of the laser medium 105. Furthermore, both ends of the laser medium 105 are in contact with the ambient air, and the temperature of the laser medium further decreases due to heat transfer between the laser medium 105 and the air. There is a problem that a difference occurs, a desired thermal lens cannot be generated in the laser medium 105, and the oscillation efficiency of the fundamental laser light at both ends of the laser medium 105 is lowered. And there was a problem that the output of the 2nd harmonic laser beam finally obtained also fell.

  The present invention has been made to solve the above-described problems, and an object of the present invention is to provide a laser light source device that can obtain a high-luminance fundamental wave output and enable high-efficiency second harmonic conversion. It is what.

  A laser light source device according to the present invention has a flat plate shape, has a waveguide structure in the thickness direction of a cross section perpendicular to the optical axis, and generates a gain for the laser light, and one surface side of the laser medium A heat sink joined to the laser medium via the clad, a semiconductor laser disposed on the optical axis of the laser medium in the vicinity of one end surface of the laser medium, and an excitation light incident on the laser medium, and an optical axis of the laser medium And a nonlinear material having a waveguide structure in the same direction as the waveguide structure of the laser medium, the laser medium having an optical axis depending on a refractive index distribution in the laser medium. And a lens effect which is an effect of arranging a plurality of lenses in a direction perpendicular to the thickness direction, and the laser light oscillates in a spatial mode due to the lens effect in a direction perpendicular to the optical axis and the thickness direction. Thus, the joint surface of the heat sink with respect to the clad has a comb structure arranged at regular intervals in a cross section perpendicular to the optical axis, and the comb width of both ends of the comb structure and the comb teeth adjacent to both ends of the comb teeth. Is configured to be narrower than the comb width of the other comb teeth, and the tips of the comb teeth of the comb structure are joined to the clad.

  According to this invention, the refractive index distribution is generated in the direction perpendicular to the optical axis in the laser medium by making the comb width of the joint part between the clad and the heat sink narrower at both ends than the center part. The fundamental wave laser output equivalent to that at the center of the laser medium can be obtained at both ends of the laser medium, and a higher-power laser light source device can be obtained.

It is a side view which shows the laser light source device which concerns on Embodiment 1 of this invention. It is sectional drawing which shows the laser light source device by Embodiment 1 of this invention. It is sectional drawing which shows the thermal radiation path | route of the laser medium by Embodiment 1 of this invention. It is sectional drawing which shows the thermal radiation path | route of the laser medium by Embodiment 1 of this invention. It is a figure which shows the laser medium internal temperature distribution by Embodiment 1 of this invention. It is a top view which shows the comb structure of the heat sink by Embodiment 2 of this invention. It is a side view of the conventional mode control waveguide type laser light source apparatus. It is sectional drawing which shows the conventional mode control waveguide type laser light source apparatus. It is a figure which shows the temperature distribution in the laser medium of the conventional mode control waveguide type laser light source apparatus.

Embodiment 1 FIG.
Hereinafter, the laser light source apparatus according to Embodiment 1 of the present invention will be described in detail with reference to FIGS.
1 and 2 are diagrams showing a configuration of a laser light source apparatus according to Embodiment 1 of the present invention. FIG. 1 is a side view, and FIG. 2 is a cross-sectional view taken along the line aa ′ of FIG. It is sectional drawing.
The laser light source device according to the first embodiment shown in FIGS. 1 and 2 has a semiconductor laser 1 that emits excitation light, a flat plate shape, and a cross-sectional thickness perpendicular to the optical axis 6 that represents the laser oscillation direction. A laser medium 5 having a waveguide structure in the vertical direction (y-axis direction), in which excitation light from the semiconductor laser 1 is incident on the waveguide structure and generates a gain for the laser light, and bonded to the lower surface of the laser medium 5 The clad 4, the heat sink 2 bonded to the lower surface of the clad 4 with the bonding material 3, and the optical medium 6 close to the optical axis 6 of the laser medium 5 are disposed in the same direction as the waveguide structure of the laser medium 5. And a non-linear material 7 having a structure.

In the laser medium 5, the shape of one end face 5a and the other end face 5b perpendicular to the optical axis 6 is, for example, rectangular, the thickness in the y-axis direction is several to several tens of μm, and the width in the x-axis direction is several. It has a size of 100 μm to several mm. For the sake of explanation, a coordinate system is used in which the long side direction of the rectangle is the x axis, the short side direction is the y axis, and the optical axis 6 direction is the z axis.
An optical film that reflects or transmits laser light having a specific wavelength is applied to the incident-side end surface 5a and the emission-side end surface 5b of the laser medium 5, respectively. The end face 5a transmits laser light having a wavelength of excitation light (for example, wavelength 808 nm) emitted from the semiconductor laser 1, and totally reflects fundamental wave laser light (for example, wavelength 1064nm) generated in the laser medium 5. An optical film is applied. The end face 5b is provided with an antireflection film that transmits the fundamental laser beam. These optical films are formed by laminating dielectric multilayer films, for example. As the laser medium 5, a general solid laser material can be used.

  In FIG. 1, the upper surface (y-axis direction) of the laser medium 5 is in contact with air. However, the second upper surface of the laser medium 5 has a smaller refractive index than the laser medium 5. A clad (not shown) may be bonded. As described above, when the second clad is bonded to the upper surface of the laser medium 5, the propagation mode in the y-axis direction of the laser medium 5 can be arbitrarily set by adjusting the refractive index difference between the laser medium 5 and the second clad. Can be adjusted. Further, if the thickness of the second cladding in the y-axis direction is set large, the rigidity of the laser medium 5 can be increased without affecting the waveguide mode of the laser medium 5.

  The clad 4 has a smaller refractive index than that of the laser medium 5 and is bonded to one surface parallel to the xz plane of the laser medium 5. The clad 4 is configured by, for example, depositing a film made of an optical material as a raw material, or optically bonding the optical material to the laser medium 5 by optical contact, diffusion bonding, or the like. Further, as the clad 4, an optical adhesive having a smaller refractive index than that of the laser medium 5 may be used.

The heat sink 2 is made of a material having high thermal conductivity, for example, silicon (Si), aluminum nitride (AlN), silicon nitride (SiC), and the joint surface of the heat sink 2 to the clad 4 is perpendicular to the optical axis 6. It has a comb structure (comb teeth) arranged at regular intervals in the cross section (xy plane), and the tips of the comb teeth of the heat sink 2 are joined to the clad 4 via the joining material 3.
Further, as shown in FIG. 2, the comb structure of the heat sink 2 is such that the comb width W2 of the both-end comb teeth 21 and the comb width W3 of the comb teeth adjacent to the both-end comb teeth 21 in the x-axis direction are other comb teeth. It is configured to be narrower than the width W1. The reason for this will be described in detail later.

  The bonding material 3 exhausts heat generated in the laser medium 5 to the heat sink 2 via the clad 4. The bonding material 3 can be realized by metal solder, an optical adhesive, a heat conductive adhesive, or the like. Metallization (attaching a metal film) may be performed on the surface of the clad 4 facing the surface to which the laser medium 5 is bonded in order to increase the bonding strength with the bonding material 3. In the case where the heat sink 2 is made of an optical material, the clad 4 and the heat sink 2 may be directly bonded by, for example, optical contact or diffusion bonding.

The semiconductor laser 1 is disposed in the vicinity of one end face 5a of the laser medium 5, and a heat sink for cooling (not shown) is joined as necessary. The size of the semiconductor laser 1 in the x-axis direction is substantially equal to the size of the laser medium 5 in the x-axis direction, and pumping light is output substantially uniformly in the x-axis direction. Excitation light emitted from the semiconductor laser 1 is incident on the laser medium 5 from one end face 5 a of the laser medium 5 in the xz plane direction and is absorbed by the laser medium 5.
The laser medium 5 generates a lens effect, which is an effect of arranging a plurality of lenses in a direction perpendicular to the optical axis 6 and the thickness direction, based on the refractive index distribution in the laser medium. The laser light oscillates in a spatial mode due to the lens effect in a direction perpendicular to the optical axis 6 and the thickness direction, and the fundamental laser light is emitted from the laser medium 5.

  The non-linear material 7 has a cross section perpendicular to the optical axis 6 substantially the same shape as the laser medium 5, has end faces 7 a and 7 b perpendicular to the optical axis 6, and one end face 7 a is the other of the laser medium 5. It arrange | positions in proximity to the end surface 5b. The end face 7a of the nonlinear material 7 is provided with an optical film that transmits the fundamental laser light and reflects the second harmonic laser light. The end face 7b of the nonlinear material 7 reflects the fundamental laser light, and An optical film that transmits the second harmonic laser beam is provided. Further, as the nonlinear material 7, a general wavelength conversion material can be used.

  Next, referring to FIGS. 3 and 4, in the laser light source device of FIG. 1, a desired temperature distribution is generated in the laser medium 5 to form a refractive index distribution in the laser medium 5, and this refractive index. A method for generating a lens effect by distribution will be described. 3 is an enlarged view of the vicinity of the central portion in the x-axis direction of the cross-sectional view (xy plane) of the heat sink 2 to the laser medium 5 in FIG. FIG. 4 is a cross-sectional view (xy plane) of the heat sink 2 to the laser medium 5 and shows the heat flow and temperature distribution when the comb widths of the two comb teeth provided on the heat sink 2 are different.

  The laser medium 5 generates heat by converting a part of the absorbed pumping light output into heat. The generated heat is exhausted to the heat sink 2 through the clad 4 and the bonding material 3. At this time, the heat sink 2 has a comb shape, and the range bonded through the bonding material 3 is only the tip portion of the comb teeth. In addition, a heat flow is generated from substantially the center of the two comb teeth toward both sides in the x-axis direction. Therefore, the temperature at the substantially middle portion between the two comb teeth becomes the maximum, and the temperature decreases as the comb tooth portion is approached. At this time, if the comb widths of the two comb teeth are the same, the laser medium temperatures on the two comb teeth are substantially the same temperature.

  The refractive index of the optical material such as the laser medium 5 changes almost in proportion to the temperature difference. When a material having a positive refractive index change dn / dT per unit temperature is used as the optical material of the laser medium 5, the temperature at the center of the two comb teeth increases, so the refractive index increases, and the comb tooth portion As the value approaches, the refractive index decreases. As a result, a thermal lens effect is generated in the x-axis direction with the center portion of the two comb teeth as the optical axis. Similarly, when a material having a negative refractive index distribution dn / dT per unit temperature is used as the optical material of the laser medium 5, the refractive index distribution is opposite to the temperature distribution, and the portion bonded to the comb teeth The refractive index is large, and the refractive index at the center of the two comb teeth is small. As a result, in the x-axis direction, a thermal lens effect is generated with the portion bonded to the comb teeth as the optical axis. Since the same effect can be obtained regardless of whether dn / dT is positive or negative, the following description will be made using the case where dn / dT is positive unless otherwise specified.

Next, the comb structure in the x-axis direction of the heat sink 2 is composed of a plurality of comb teeth arranged at almost equal intervals. As shown in FIG. 2, the comb width W2 of the comb teeth 21 at both ends of the heat sink 2 is shown. The comb width W3 of the comb tooth adjacent to the inner side (inner side) is different from the comb width W1 of the other central comb teeth. Here, when the comb width of the comb teeth at the center is W1, and the comb widths of both ends and adjacent comb teeth are W2 and W3, the comb widths are set so that W2 and W3 <W1.
The comb width W2 of the both-end comb teeth 21 is the same as or narrower than the comb width W3 of the adjacent (inner) comb teeth.

  Here, as shown in FIG. 4, for example, when a comb tooth having a comb width W1 and a comb tooth having a comb width W3 smaller than the comb width W1 are adjacent to each other, the amount of heat that can be exhausted from the comb teeth having a comb width W3. Therefore, the temperature of the laser medium 5 on the comb teeth having the comb width W3 is higher than the temperature of the laser medium 5 on the comb teeth having the comb width W1. That is, in FIG. 2, the temperature distribution can be corrected by adjusting the comb widths W2 and W3 of the comb teeth 21 at both ends of the heat sink 2 and the adjacent comb teeth.

Here, a calculation example of the temperature distribution of the laser medium 5 when the comb width W2 = W3 = 80 μm of the comb teeth 21 adjacent to the both ends comb teeth 21 of the heat sink 2 and the other comb width W1 = 90 μm is shown. As shown in FIG. As the laser medium 5, Nd: YVO4 is used, and other calculation conditions are as follows: the number of comb teeth of the heat sink 2 = 16, the center distance of the comb teeth = 200 μm, and comb teeth in the direction of the optical axis 6 at room temperature of 25 ° C. The case where the length is 1.5 mm and the total heat generation amount in the laser medium 5 is 6.4 W is shown.
As shown in FIG. 5, in the x-axis direction in the laser medium 5, the temperature of the center portion of the two comb teeth and the temperature of the comb teeth are substantially equal in both end portions and the center portion of the laser medium 5. (Temperature difference) is obtained, and it can be seen that a uniform thermal lens can be generated between the comb teeth.

When the design value such as the amount of heat generated in the laser medium 5 (laser output of excitation light) changes, the comb widths of the comb teeth 21 at both ends of the heat sink 2 and the adjacent comb teeth are adjusted to periodically A uniform temperature distribution can be formed, and a plurality of uniform thermal lenses can be generated in the laser medium 5.
Furthermore, if the thermal lens effect varies between each comb tooth only by adjusting the comb widths of the both end comb teeth and the adjacent comb teeth, the comb width of the inner comb teeth may be further changed. Thus, it is possible to adjust so as to obtain a periodic lens effect.

  With this configuration, a uniform thermal lens is generated between the comb teeth by forming a temperature distribution with a substantially constant period in the x-axis direction in the laser medium 5, and the x-axis of the laser medium 5. The fundamental laser output that oscillates in the vicinity of both end portions in the direction can be improved to the same extent as the central portion, and the laser output can be improved as a whole laser light source device.

Embodiment 2. FIG.
Next, a laser light source apparatus according to Embodiment 2 of the present invention will be described in detail with reference to FIG.
FIG. 6 is a view of the heat sink 2 of the laser light source apparatus according to Embodiment 2 of the present invention as viewed from above. In the laser light source device of the second embodiment, the comb width of the comb teeth provided in the heat sink 2 is larger than the first embodiment in the direction of the optical axis of the laser medium 5 from the incident-side end surface 5a. The difference is that the width of the comb gradually narrows toward the end face 5b. Other configurations are the same as those of the first embodiment, and the same or corresponding parts are denoted by the same reference numerals and description thereof is omitted.

The comb teeth provided on the heat sink 2 have a trapezoidal shape in which the comb width of the comb teeth is different in the direction of the optical axis 6, and the comb width on the side of the end face 5a on which the excitation light from the semiconductor laser 1 is incident is W1, W2 and W3 are the comb teeth at both ends and the adjacent comb teeth. On the other hand, the width of the comb on the side of the end face 5b from which the fundamental laser beam generated in the laser medium 5 is emitted is W1 ′ at the center, and W2 ′ and W3 ′ at the comb teeth adjacent to both ends and both ends. , W1 ′ <W1, W2 ′ <W2, and W3 ′ <W3 are set.
That is, the comb widths W1, W2, and W3 of the heat sink 2 on the side to which the semiconductor laser 1 is adjacent are comb widths W1 ′, W2 ′, and W3 of the comb tooth on the side on which the nonlinear material 7 is adjacent. 'Be different from each other to become wider.

  By adopting such a configuration, it is possible to secure a sufficient temperature difference between the central portion of each comb tooth on the end surface 5b on the nonlinear material 7 side and the temperature on the comb tooth in the laser medium 5, and the thermal lens The adjustment range can be expanded and controllability is improved.

  Although the embodiments of the present invention have been described above, the present invention is not limited to the embodiments, and various design changes can be made. Within the scope of the present invention, each embodiment These embodiments can be freely combined, and each embodiment can be modified or omitted as appropriate.

1: semiconductor laser, 2: heat sink, 3: bonding material, 4: clad,
5: Laser medium 5a: Incident side end surface of the laser medium, 5b: Output side end surface of the laser medium,
6: optical axis, 7: nonlinear material, 7a: incident end face of nonlinear material,
7b: Output side end face of nonlinear material

Claims (3)

It has a flat plate shape, has a waveguide structure in the thickness direction of the cross section perpendicular to the optical axis, and is joined to one surface side of the laser medium via a cladding. A heat sink, a semiconductor laser disposed adjacent to one end face of the laser medium on the optical axis of the laser medium, and an excitation light incident on the laser medium; and a laser diode on the optical axis of the laser medium. A non-linear material disposed near the other end face and having a waveguide structure in the same direction as the waveguide structure of the laser medium,
The laser medium generates a lens effect, which is an effect of arranging a plurality of lenses in a direction perpendicular to the optical axis and the thickness direction, based on a refractive index distribution in the laser medium. Oscillates in a spatial mode due to the lens effect in a direction perpendicular to the axis and the thickness direction,
The joint surface of the heat sink with respect to the clad has a comb structure arranged at regular intervals in a cross section perpendicular to the optical axis, and the comb width of both ends of the comb structure and the comb teeth adjacent to both ends of the comb teeth Is configured to be narrower than the comb width of the other comb teeth, and the tip of the comb teeth of the comb structure is joined to the clad.   2. The bonding surface of the heat sink, wherein a comb width of a comb tooth on a side where the semiconductor laser is adjacent is different from a comb width of a comb tooth on a side where the nonlinear material is disposed in proximity. The laser light source device described. The comb width of the comb teeth of the heat sink on the side where the semiconductor laser is close is wider than the comb width of the comb teeth on the side where the nonlinear material is close. Laser light source device.

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