JP2015050368A - Laser module, solid-state laser device, and manufacturing method of laser module - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a laser module capable of inhibiting the deterioration of characteristics and reliability which results from heat generated by a laser crystal, and to provide a solid-state laser device and a manufacturing method of the laser module.SOLUTION: The laser module includes: a laser crystal; a heat dissipation metal film disposed on a joint surface of the laser crystal; a wavelength conversion element which is joined to the joint surface at an opening part provided on the heat dissipation metal film and forms an optical resonator with the laser crystal; and a heat sink contacting with the heat dissipation metal film. At least the heat dissipation metal film is disposed on a portion of the joint surface which excludes a region where the wavelength conversion element is disposed.

Description

  The present invention relates to a laser module in which a laser crystal and a wavelength conversion element are bonded, a solid-state laser device, and a method for manufacturing the laser module.

  A laser module in which a laser crystal and a wavelength conversion element are combined and integrated, and a solid-state laser device equipped with this laser module are known. The laser crystal that is excited by the output light of the semiconductor laser and outputs oscillation light and the wavelength conversion element that outputs the harmonic light of this oscillation light are joined with the optical axis aligned at a predetermined angle to form a laser module. The In addition, in order to join the laser crystal and the wavelength conversion element, there is a method of performing autonomous alignment using the surface tension of the droplets by superimposing both joint surfaces with the droplets sandwiched therebetween (for example, Patent Document 1). reference.).

  In order to dissipate the heat generated in the laser crystal, a method of fixing a heat sink to the side surface of the laser crystal has been proposed (for example, see Patent Document 2).

JP 2012-88631 A Japanese Patent Laid-Open No. 7-79039

  When different types of optical crystals such as laser crystals and wavelength conversion elements are bonded by optical contact, it is necessary to reduce the crystal size in consideration of the difference in linear expansion coefficient of each optical crystal. In order to reduce optical noise, the laser crystal is preferably thin. Therefore, there is a limit to heat radiation from the side surface of the laser crystal.

  For this reason, as the output of the solid-state laser device increases, the heat generated in the laser crystal causes an increase in element temperature and a shift in oscillation wavelength. As a result, there are problems such as a decrease in output efficiency and a decrease in wavelength stability.

  In view of the above problems, an object of the present invention is to provide a laser module, a solid-state laser device, and a method for manufacturing a laser module, in which deterioration in characteristics and reliability due to heat generated in a laser crystal is suppressed.

  According to one aspect of the present invention, (b) a laser crystal, (b) a heat dissipating metal film disposed on the bonding surface of the laser crystal, and (c) an opening provided in the heat dissipating metal film on the bonding surface. A wavelength conversion element that is bonded and forms an optical resonator together with the laser crystal; and (d) a heat sink that contacts the heat dissipation metal film, and at least radiates heat on the remaining area of the area where the wavelength conversion element is disposed on the bonding surface. A laser module in which a metal film is disposed is provided.

  According to another aspect of the present invention, (b) a semiconductor laser that emits excitation light, (b) a laser crystal that is excited by the excitation light and outputs oscillation light, and a heat dissipation disposed on the bonding surface of the laser crystal. A metal film, a wavelength conversion element that generates an optical resonator together with a laser crystal by being bonded to a bonding surface through an opening provided in the heat dissipation metal film, and a heat sink that contacts the heat dissipation metal film. And a solid state laser device comprising: a laser module having at least a heat dissipating metal film on a remaining region of the region where the wavelength conversion element on the bonding surface is disposed.

  According to still another aspect of the present invention, (b) a step of forming a heat dissipation metal film on the bonding surface of the laser crystal, and (b) the heat dissipation metal film along the outer edge shape of the bonding end surface of the wavelength conversion element. A step of forming an opening; (c) a step of filling a droplet in the opening; and (d) superimposing the bonding surface of the laser crystal and the bonding end surface of the wavelength conversion element through the droplet in the opening, A step of autonomously aligning the laser crystal and the wavelength conversion element by the surface tension of the liquid droplet, a step of (e) bonding the laser crystal and the wavelength conversion element, and (f) a heat sink so as to be in contact with the heat dissipation metal film. A method for manufacturing a laser module is provided.

  ADVANTAGE OF THE INVENTION According to this invention, the manufacturing method of the laser module, the solid state laser apparatus, and laser module by which the fall resulting from the characteristic and reliability resulting from the heat which generate | occur | produces in a laser crystal was suppressed can be provided.

It is a schematic diagram which shows the structure of the laser module which concerns on embodiment of this invention. It is a typical front view of the laser module which concerns on embodiment of this invention. It is a flowchart for demonstrating the manufacturing method of the laser module which concerns on embodiment of this invention. 4A and 4B are schematic views for explaining a method for manufacturing a laser module according to an embodiment of the present invention, in which FIG. 4A is a perspective view and FIG. 4B is a cross-sectional view of an opening of a heat dissipation metal film. It is a schematic diagram which shows the shape of the joint surface of an optical element. It is a schematic diagram which shows the structure of the laser module of a comparative example. It is a schematic diagram which shows the structural example of the solid-state laser apparatus carrying the laser module which concerns on embodiment of this invention. It is a schematic diagram which shows the structure of the laser module which concerns on other embodiment of this invention.

  Embodiments of the present invention will be described with reference to the drawings. In the following description of the drawings, the same or similar parts are denoted by the same or similar reference numerals. However, it should be noted that the drawings are schematic. Further, the embodiments described below exemplify apparatuses and methods for embodying the technical idea of the present invention, and the embodiments of the present invention include the material, shape, structure, arrangement, etc. of components. Is not specified as follows. The embodiment of the present invention can be variously modified within the scope of the claims.

  As shown in FIG. 1, a laser module 1 according to an embodiment of the present invention includes a laser crystal 10 having a bonding surface 11, a heat radiating metal film 20 disposed on the bonding surface 11 of the laser crystal 10, and a heat radiating metal film. 20 is provided with a wavelength conversion element 30 that is bonded to the bonding surface 11 through an opening provided in 20 and forms an optical resonator together with the laser crystal 10, and a heat sink 40 that contacts the heat radiating metal film 20. The laser module 1 has a structure in which the laser crystal 10 and the wavelength conversion element 30 are integrated by an optical contact method or the like.

  The area of the bonding surface 11 of the laser crystal 10 to which the wavelength conversion element 30 is bonded is wider than the area of the end surface (hereinafter referred to as “bonding end surface 31”) of the wavelength conversion element 30 bonded to the laser crystal 10. The heat radiating metal film 20 is disposed on the remaining area of the bonding surface 11 where the wavelength conversion element 30 is disposed.

  In the laser module 1, the laser crystal 10 outputs oscillation light when excited by excitation light L1 incident from the outside. Then, the wavelength conversion element 30 generates harmonic light of the oscillation light, and outputs this harmonic light as the output light L2. A first reflective film 15 is disposed on the incident surface 12 of the laser crystal 10 that is opposite to the bonding surface 11 and on which the excitation light L1 is incident. In addition, a second reflective film 35 is disposed on the output surface 32 of the wavelength conversion element 30 that outputs the output light L <b> 2 and faces the bonding end surface 31. Details of the first reflective film 15 and the second reflective film 35 will be described later.

  For example, as shown in FIG. 1, the heat sink 40 is disposed so as to cover the side surface 13 of the laser crystal 10, the side surface 33 of the wavelength conversion element 30, and a part of the bonding surface 11 of the laser crystal 10. On the bonding surface 11 of the laser crystal 10, the heat radiating metal film 20 and the heat sink 40 are in contact with each other in a region where the wavelength conversion element 30 is not disposed. In the laser module 1, heat generated in the laser crystal 10 is radiated from the heat sink 40 through the heat radiating metal film 20. That is, the heat dissipation from the side other than the side surface 13 of the laser crystal 10 is improved, and heat is efficiently dissipated to the heat sink 40. For this reason, heat dissipation improves, so that the junction surface 11 is widened.

  As a material for the heat dissipation metal film 20, a metal having good adhesion to the laser crystal 10 and high thermal conductivity is used. For example, chromium (Cr), nickel (Ni), gold (Au), aluminum (Al), indium (In), tantalum (Ta), or the like is employed. The film thickness of the heat dissipation metal film 20 is, for example, about 0.1 μm to 1 μm.

  The heat sink 40 is bonded and fixed to the laser crystal 10 and the wavelength conversion element 30 by using an adhesive having high thermal conductivity, a silver paste, an indium sheet, or the like. The heat sink 40 is preferably made of a material having high thermal conductivity and easy to process. For example, a copper (Cu) material, an aluminum (Al) material, or a silicon (Si) material having a thermal conductivity equal to or higher than glass is used for the heat sink 40.

  Since heat is radiated from the heat sink 40 through the heat radiating metal film 20, the heat radiation from the side surface 13 of the laser crystal 10 may not be high. Therefore, the thickness of the laser crystal 10 can be reduced. As the laser crystal 10 is thinner, the optical noise can be reduced. For example, the laser crystal 10 having a thickness of about 0.3 mm can be used. It is known that optical noise is reduced by setting the thickness of the laser crystal 10 to 0.3 mm or less. Further, since the laser crystal 10 can be reduced in size, when the laser crystal 10 and the wavelength conversion element 30 are bonded by the optical contact method, the influence due to the difference in linear expansion coefficient between the laser crystal 10 and the wavelength conversion element 30 is suppressed. .

The laser crystal 10 is, for example, a yttrium vanadate (Nd: YVO ₄ ) crystal doped with neodymium (Nd) ions. The Nd: YVO ₄ crystal is preferably used to obtain the green output light L2. In addition, yttrium aluminum garnet (Nd: YAG) crystal, gadolinium vanadate (Nd: GdV04) crystal, lithium yttrium fluoride (Nd: YLF) crystal, etc. doped with Nd ions can also be used for the laser crystal 10. It is.

  The first reflective film 15 disposed on the incident surface 12 of the laser crystal 10 is a laser coating film corresponding to the wavelengths of the excitation light L1 and the output light L2. For example, an antireflection film (AR coat) corresponding to the excitation light L1 having a wavelength of 809 nm, or a high reflection film (HR coat) corresponding to a fundamental wave having a wavelength of 1064 nm and second harmonic generation light (SHG light) having a wavelength of 532 nm. Etc.

  As the wavelength conversion element 30, a quasi phase matching crystal in which a periodic polarization inversion structure is formed in a ferroelectric crystal can be used. For example, lithium tantalate (LT) crystal, lithium niobate (LN) crystal, or LT crystal or LN crystal doped with magnesium oxide (MgO) is used (MgLT, MgSLT, MgLN, MgSLN).

  The LT crystal or LN crystal employed in the wavelength conversion element 30 can be of congruent composition (coincidence melting composition) or stoichiometric composition (stoichiometric composition). For example, in the case of an LT crystal, the coercive electric field is reduced to about 1/10 by using the stoichiometric composition. That is, the applied voltage can be reduced to 1/10.

  In addition, light damage resistance can be improved by adding magnesium (Mg), zinc (Zn), scandium (Sc), indium (In), or the like to the LT crystal or the LN crystal. In the case of an LN crystal, the coercive electric field can be reduced to about a quarter by adding about 5 mol% of Mg. Thereby, the applied voltage can be reduced to about a quarter.

  For example, a wavelength conversion crystal (PPMgSLT crystal) in which a domain-inverted structure is formed in a period (for example, a period of 8 μm) in which a desired phase matching temperature is obtained in the MgSLT crystal is used for the wavelength conversion element 30. In this case, it is preferable that the crystal length be sufficient to cover the fundamental wave oscillation spectrum width, and the length of the wavelength conversion crystal is about 1 mm.

  The laser module 1 is manufactured by the manufacturing method described in Japanese Patent Application Laid-Open No. 2007-225786, and the wavelength conversion element 30 and the laser crystal 10 are integrated with the wavelength conversion crystal 301 sandwiched between the dummy materials 302. It may be. By adopting a structure in which the wavelength conversion crystal 301 is sandwiched between the dummy materials 302, the junction region of the wavelength conversion element 30 with the laser crystal 10 increases. Thereby, compared with the case where only the wavelength conversion crystal 301 is joined to the laser crystal 10, the wavelength conversion element 30 and the laser crystal 10 can be joined easily.

  The second reflective film 35 disposed on the output surface 32 of the wavelength conversion element 30 is a laser coating film corresponding to the wavelengths of the excitation light L1 and the output light L2. For example, a high reflection film (HR coat) corresponding to a fundamental wave having a wavelength of 1064 nm, an antireflection film (AR coat) corresponding to SHG light having a wavelength of 532 nm, or the like.

In the laser module 1, for example, an Nd: YVO ₄ crystal is used as the laser crystal 10, and oscillation light having a wavelength of about 1064 nm is excited by the excitation light L 1. At this time, the wavelength of the excitation light L1 is set to a wavelength with high absorption efficiency in the laser crystal 10, for example, about 809 nm. The oscillation light generated in the laser crystal 10 is wavelength-converted into SHG light having a wavelength of about 532 nm by the wavelength conversion element 30, and the green output light L 2 is output from the laser module 1.

FIG. 2 shows a view of the laser module 1 viewed from the incident surface 12 side. According to the investigation by the present inventors, when the size of the bonding surface 11 of the laser crystal 10 is 1.4 mm × 1.4 mm or more, heat dissipation is a region where the wavelength conversion element 30 of the bonding surface 11 is not bonded. When the area of the region S was 1.2 mm ² or more, SHG light was stably obtained with high efficiency. Further, it has been confirmed by the present inventors that when the power of the output light L2 exceeds 100 mW, the SHG light can be stably obtained if the area of the heat radiation region S is about 2 mm ² or more.

By the way, the Nd: YVO ₄ crystal has anisotropy in thermal conductivity such that the c-axis direction has a higher thermal conductivity than the a-axis direction. For this reason, in order to suppress the ovalization of the oscillation light output from the laser crystal 10 using the Nd: YVO ₄ crystal, it is preferable that the bonding surface 11 has a rectangular shape having a long side in the c-axis direction. For example, the joint surface 11 is a rectangle whose long side in the c-axis direction is 1.7 mm and whose short side perpendicular to the c-axis direction is 1.2 mm.

  The laser module 1 can be manufactured using autonomous alignment, as will be described below. The “autonomous alignment” is a method in which two optical elements are autonomously aligned by superimposing the joint surfaces of the two optical elements with each other through the droplets and using the surface tension of the droplets. An example of the manufacturing method of the laser module 1 will be described with reference to the flowchart of FIG.

  First, in step S1, the heat radiating metal film 20 is formed on the bonding surface 11 of the laser crystal 10 to which the wavelength conversion element 30 is bonded. Next, in step S <b> 2, an opening is formed in the heat radiating metal film 20 along the outer edge shape of the joining end face 31 of the wavelength conversion element 30 that is joined to the laser crystal 10.

  In step S3, the opening is filled with droplets. Pure water or the like is used for the droplets. Next, in step S4, the bonding surface 11 of the laser crystal 10 and the bonding end surface 31 of the wavelength conversion element 30 are overlapped with each other at the opening of the heat dissipation metal film 20 via the droplet, and the laser crystal 10 is applied by the surface tension of the droplet. And the wavelength conversion element 30 are autonomously aligned. Then, the laser crystal 10 and the wavelength conversion element 30 are joined by, for example, an optical contact method. Alternatively, the laser crystal 10 and the wavelength conversion element 30 may be bonded using an adhesive. However, considering the optical axis shift between the laser crystal 10 and the wavelength conversion element 30 due to the presence of an adhesive between the laser crystal 10 and the wavelength conversion element 30, the attenuation of light due to transmission through the adhesive, and the like. The laser crystal 10 and the wavelength conversion element 30 are preferably bonded by an optical contact method.

  Further, in step S5, the heat sink 40 is disposed so as to be in contact with the heat radiating metal film 20. Then, the heat sink 40 is fixed to the laser crystal 10 or the wavelength conversion element 30 with an adhesive or the like. Thus, the laser module 1 is completed.

  In the above, the example in which the heat sink 40 is fixed to the laser crystal 10 or the wavelength conversion element 30 after the laser crystal 10 and the wavelength conversion element 30 are bonded to each other has been described. However, after fixing the heat sink 40 to the laser crystal 10, the laser crystal 10 and the wavelength conversion element 30 may be joined.

  In addition to pure water, for example, an adhesive having a viscosity close to that of water may be used for the droplet filled in the opening of the heat dissipation metal film 20.

  According to the manufacturing method described above, in the opening formed in the heat dissipation metal film 20, the region exposed to the opening of the laser crystal 10 and the wavelength conversion element 30 are autonomously aligned by the surface tension. As a result, it is easy to join the laser crystal 10 and the wavelength conversion element 30 at a predetermined angle with high accuracy. For example, the c-axis direction of the laser crystal 10 and the wavelength conversion element 30 can be made the same.

  4A and 4B show a part of a process in which the laser crystal 10 and the wavelength conversion element 30 are joined by adjusting the c-axis angle by autonomous alignment. FIG. 4A and FIG. 4B are examples of a state in which the droplet 50 is filled in the opening 21 formed in the heat dissipation metal film 20.

  In the example shown in FIGS. 4A and 4B, four openings 21 are formed in the heat dissipation metal film 20 disposed on the laser crystal 10. The opening 21 is formed as follows, for example. That is, after the heat dissipation metal film 20 is formed on the entire bonding surface 11 of the laser crystal 10, a photosensitive resist film is applied on the heat dissipation metal film 20. The film thickness of the photosensitive resist film is, for example, about several μm. Then, after patterning the photosensitive resist film by a photolithography technique, openings 21 are formed in the heat dissipation metal film 20 using the photosensitive resist film as a mask.

  As shown in FIG. 4A, after forming a plurality of openings 21 in one laser crystal 10, the wavelength conversion element 30 is bonded to the bonding surface 11 of the laser crystal 10 exposed in each opening 21. Thereafter, the laser crystal 10 is divided. In this way, by forming the plurality of openings 21 in the heat dissipation metal film 20 at the same time, a plurality of joining can be performed in one operation. Thereby, productivity can be remarkably improved.

  As shown in FIG. 4A, the bonding surface 11 of the laser crystal 10 is set so that the c-axis direction of the laser crystal 10 is a long side. As described above, this is for suppressing ovalization of the oscillation light caused by the thermal conductivity anisotropy of the laser crystal 10. Then, the laser crystal 10 and the wavelength conversion element 30 are joined with the c-axis direction of the wavelength conversion element 30 aligned with the c-axis direction of the laser crystal 10.

  In the autonomous alignment, in order to join the c-axis directions of the two optical elements at a desired angle, the shape of the joining surface P of the optical element has a ratio of the long side A to the short side B as shown in FIG. A rectangular shape of 5: 4 to 5: 3 is preferable. When the ratio of the short side B to the long side A is larger than 5: 4, the optical elements may be aligned in a direction different by 90 degrees. When the ratio of the short side B to the long side A is smaller than 5: 3, the result is that the heat dissipation is reduced.

  In order to obtain the surface tension of the droplet 50 necessary for autonomous alignment, the difference in wettability between the photosensitive resist used for forming the opening 21 in the heat dissipation metal film 20 and the laser crystal 10 is used. It is effective to do. That is, autonomous alignment is performed in a state where the photosensitive resist is formed on the heat dissipation metal film 20. As a result, the depth of the opening 21 becomes the combined depth of the film thickness of the heat dissipation metal film 20 and the film thickness of the photosensitive resist, which is more liquid than the depth of only the film thickness of the heat dissipation metal film 20. The surface tension of the droplet 50 increases. As a result, autonomous alignment can be performed better. When this method is adopted, the photosensitive resist on the heat dissipation metal film 20 is not removed even after the opening 21 is formed, and the photosensitive resist is removed after the laser crystal 10 and the wavelength conversion element 30 are connected. To do.

  As already described, the shape of the joint end surface 31 of the wavelength conversion element 30 is preferably a rectangular shape having a ratio of the long side to the short side of 5: 4 to 5: 3. In this case, the outer edge of the joint end surface 31 The shape of the opening 21 formed along the shape is also a rectangular shape having a ratio of the long side to the short side of 5: 4 to 5: 3.

  In addition, it is preferable that the gap | interval of the joining end surface 31 joined to the laser crystal 10 of the wavelength conversion element 30 and the opening part 21 of the thermal radiation metal film 20 is about 0.2 mm-0.5 mm. That is, when the joining end surface 31 and the opening 21 are rectangular, the difference in length between the sides is set to about 0.2 mm to 0.5 mm.

For example, the joint end surface 31 of the wavelength conversion element 30 is a rectangular shape having a c-axis direction of 1 mm and a direction orthogonal to the c-axis direction of 0.8 mm. When the gap is 0.5 mm, the opening 21 has a rectangular shape in which the c-axis direction is 1.5 mm and the direction orthogonal to the c-axis direction is 1.3 mm. When the joining surface 11 of the laser crystal 10 is 2 mm × 2 mm, the area of the heat dissipation region where the heat dissipation metal film 20 is disposed is (2 × 2-1.5 × 1.3) mm ^2, which is about 2 mm ^2. It is. As already described, when the area of the heat dissipation region is about 2 mm ² or more, SHG light exceeding 100 mW can be stably obtained.

Further, when the joint end face 31 of the wavelength conversion element 30 is 1 mm × 0.6 mm and the gap is 0.2 mm, the opening 21 has a c-axis direction of 1.2 mm and a direction orthogonal to the c-axis direction. Is 0.8 mm. At this time, if the bonding surface 11 of the laser crystal 10 is 1.4 mm × 1.4 mm, the area of the heat dissipation region where the heat dissipation metal film 20 is disposed is 1 mm ² .

  If the gap between the joint end surface 31 of the wavelength conversion element 30 and the opening 21 of the heat dissipation metal film 20 is shorter than 0.2 mm, it is difficult to align the joint end surface 31 and the opening 21. On the other hand, if the gap is longer than 0.5 mm, the surface tension of the droplets becomes insufficient, and it may be difficult to perform autonomous alignment appropriately.

  As described above, in the laser module 1 according to the embodiment of the present invention, heat is dissipated from the heat sink 40 via the heat dissipating metal film 20 disposed on the bonding surface 11 of the laser crystal 10. Therefore, in the laser module 1, heat dissipation is performed efficiently. As a result, deterioration in characteristics and reliability due to heat generated in the laser crystal 10 is suppressed.

  For comparison with the laser module 1, for example, consider the case of a laser module 1A as shown in FIG. In the laser module 1A, the wavelength conversion element 30A is larger than the laser crystal 10A at the bonding surface. The first reflective film 15A is disposed on the laser crystal 10A, and the second reflective film 35A is disposed on the wavelength conversion element 30A.

  As shown in FIG. 6, in the laser module 1A, only the side surface 13A of the laser crystal 10A is in contact with the heat sink 40A. Therefore, compared with the laser module 1 shown in FIG. 1, in the laser module 1A shown in FIG. 6, the heat from the laser crystal 10A is not easily radiated. As a result, degradation of characteristics and reliability occurs.

  The laser module 1 can be mounted on a solid-state laser device 100, for example, as shown in FIG. The solid-state laser device 100 includes a semiconductor laser 101 and a laser module 1 according to an embodiment of the present invention.

  The semiconductor laser 101 is driven by the laser driving device 102 to emit the excitation light L1. The excitation light L1 emitted from the semiconductor laser 101 is condensed by the condenser lens 103, and the condensed excitation light L1 is incident on the laser module 1.

  The laser module 1 is excited by the excitation light L1 and generates output light L2. That is, the laser crystal 10 is excited by the excitation light L1 and outputs oscillation light, and the wavelength conversion element 30 generates harmonic light of the oscillation light. This harmonic light is output from the solid-state laser device 100 as output light L2.

  The temperature adjustment device 104 adjusts the temperature of the semiconductor laser 101 and the temperature of the laser module 1. For example, the temperature of the semiconductor laser 101 is set so that the single longitudinal mode excitation light L1 having a constant wavelength is emitted at a specific set output value without causing a mode hop. In addition, the temperature of the laser module 1 is set so that the output light L2 having the maximum output efficiency and the optical noise of a certain value or less is emitted. At this time, when the output value of the excitation light L1 is the set output value, the output light L2 is a predetermined output value.

  The semiconductor laser 101, the laser module 1, and the temperature adjustment device 104 are mounted on a support base 110. By adjusting the temperature of the support base 110 by the temperature adjusting device 104, the temperature of the laser module 1 is adjusted together with the temperature of the semiconductor laser 101. For the support base 110, a material having high thermal conductivity, such as an aluminum material or an invar material, can be used. The temperature adjustment device 104 can employ a configuration using, for example, a Peltier element. The temperature adjustment device 104 is driven by a temperature adjustment drive device 105.

The temperatures of the semiconductor laser 101 and the laser module 1 are detected by the temperature detection device 106 attached to the support base 110. Temperature sensing device 106 transmits to the controller 107 of the detected temperature as an electrical temperature signal S _T. As the temperature detection device 106, for example, a thermistor can be employed.

By receiving a temperature signal S _T, the control unit 107 can monitor the temperature of the semiconductor laser 101 and the laser module 1 in real time. The control device 107 controls the temperature adjustment drive device 105 so that the temperature of the semiconductor laser 101 and the laser module 1 is a predetermined set temperature.

The output light L2 emitted from the laser module 1 is split by the beam splitter 108. Part of the split output light L2 is incident on the light receiving element 109 and converted into an electrical signal. The light receiving element 109 transmits an electrical output signal S _p in accordance with the output value of the output light L2 to the control unit 107. For example, a photodiode can be used as the light receiving element 109.

By receiving the output signal S _p, the controller 107 can monitor the output value of the output light L2 in real time. The control device 107 controls the laser driving device 102 in order to adjust the output of the excitation light L1 of the semiconductor laser 101 so that the output value of the output light L2 is within a predetermined range.

  As described above, in the solid-state laser device 100, the control device 107 controls the laser driving device 102 so that the output light L2 has a predetermined output value, and the temperatures of the semiconductor laser 101 and the laser module 1 are predetermined. The temperature control driving device 105 is controlled so as to be the set temperature.

  According to the solid-state laser device 100 on which the laser module 1 is mounted, deterioration in characteristics and reliability due to heat generated in the laser crystal 10 is suppressed. For example, since the laser crystal 10 can be made thin, output light L2 with reduced optical noise can be obtained. Specifically, green laser output light with a low noise of 0.2% rms or less in a high output region of 100 mW can be extracted efficiently and stably.

(Other embodiments)
As mentioned above, although this invention was described by embodiment, it should not be understood that the description and drawing which form a part of this indication limit this invention. From this disclosure, various alternative embodiments, examples and operational techniques will be apparent to those skilled in the art.

  For example, as shown in FIG. 8, the periphery of the laser crystal 10 and the wavelength conversion element 30 may be covered with a heat sink 40 in a wide range as long as the progress of the excitation light L1 and the output light L2 is not hindered. In the laser module 1 shown in FIG. 8, the heat radiating metal film 20 is also disposed on the incident surface 12 of the laser crystal 10, and a part of the heat sink 40 is disposed on the incident surface 12 through the heat radiating metal film 20. . Further, a part of the heat sink 40 is also disposed on the output surface 32 of the wavelength conversion element 30. However, the heat radiating metal film 20 and the heat sink 40 are not disposed in the region where the excitation light L1 of the incident surface 12 is incident, and the heat sink 40 is not disposed in the region of the output surface 32 where the output light L2 is output.

  In the case of the configuration shown in FIG. 8, heat is also released from the incident surface 12 to the heat sink 40, so that heat dissipation is improved. Further, after the laser crystal 10 and the heat sink 40 are bonded using a solder having good thermal conductivity, the laser crystal 10 and the wavelength conversion element 30 can be joined. For this reason, a high temperature load applied to the wavelength conversion element 30 after joining with the laser crystal 10 can be avoided.

  As described above, the present invention naturally includes various embodiments not described herein. Therefore, the technical scope of the present invention is defined only by the invention specifying matters according to the scope of claims reasonable from the above description.

DESCRIPTION OF SYMBOLS 1 ... Laser module 10 ... Laser crystal 11 ... Bonding surface 15 ... 1st reflection film 20 ... Radiation metal film 21 ... Opening part 30 ... Wavelength conversion element 31 ... Bonding end surface 35 ... 2nd reflection film 40 ... Heat sink 50 ... Liquid Drop 100 ... Solid laser device 101 ... Semiconductor laser 301 ... Wavelength conversion crystal 302 ... Dummy material L1 ... Excitation light L2 ... Output light

Claims (20)

A laser crystal;
A heat dissipating metal film disposed on the bonding surface of the laser crystal;
A wavelength conversion element that is bonded to the bonding surface at an opening provided in the heat dissipation metal film and forms an optical resonator together with the laser crystal;
And a heat sink in contact with the heat radiating metal film, wherein at least the heat radiating metal film is disposed on a remaining region of the bonding surface where the wavelength conversion element is disposed.   2. The laser module according to claim 1, wherein the shape of the opening of the heat dissipation metal film is a rectangular shape having a ratio of a long side to a short side of 5: 4 to 5: 3.   The laser module according to claim 2, wherein a direction in which the long side extends is parallel to a c-axis direction of the laser crystal.   4. The gap according to claim 1, wherein a gap between a joining end face of the wavelength conversion element joined to the laser crystal and the opening of the heat dissipation metal film is 0.2 mm or more. 5. Laser module.   The laser module according to any one of claims 1 to 4, wherein the heat sink is disposed so as to cover side surfaces of the laser crystal and the wavelength conversion element.   The heat dissipation metal film is disposed on an incident surface facing the bonding surface of the laser crystal, and a part of the heat sink is disposed on the incident surface via the heat dissipation metal film. Item 6. The laser module according to any one of Items 1 to 5.   7. The laser crystal and the wavelength conversion element are bonded by autonomous alignment by a surface tension of a droplet filled in the opening provided in the heat dissipation metal film. The laser module according to any one of the above. A semiconductor laser that emits excitation light; and
A laser crystal that is excited by the excitation light and outputs oscillation light, a radiating metal film disposed on the bonding surface of the laser crystal, and the laser that is bonded to the bonding surface at an opening provided in the radiating metal film An optical resonator is formed together with the crystal, and includes a wavelength conversion element that generates harmonic light of the oscillation light, and a heat sink that is in contact with the heat dissipation metal film, and the remainder of the region where the wavelength conversion element is disposed on the joint surface A solid state laser device comprising: a laser module having at least the heat dissipating metal film disposed on the region.   9. The solid-state laser device according to claim 8, wherein the shape of the opening of the heat dissipation metal film is a rectangular shape having a ratio of a long side to a short side of 5: 4 to 5: 3.   The solid-state laser device according to claim 9, wherein a direction in which the long side extends is parallel to a c-axis direction of the laser crystal.   11. The gap according to claim 8, wherein a gap between a joining end face of the wavelength conversion element joined to the laser crystal and the opening of the heat dissipation metal film is 0.2 mm or more. Solid state laser device.   The solid-state laser device according to claim 8, wherein the heat sink is disposed so as to cover side surfaces of the laser crystal and the wavelength conversion element.   The heat dissipation metal film is disposed on an incident surface facing the bonding surface of the laser crystal, and a part of the heat sink is disposed on the incident surface via the heat dissipation metal film. Item 13. The solid-state laser device according to any one of Items 8 to 12.   14. The laser crystal and the wavelength conversion element are bonded by autonomous alignment by a surface tension of a droplet filled in the opening provided in the heat dissipation metal film. The solid-state laser device according to any one of the above. In a method for manufacturing a laser module for joining a laser crystal and a wavelength conversion element,
Forming a heat dissipating metal film on the bonding surface of the laser crystal;
Forming an opening along the outer edge shape of the joint end face of the wavelength conversion element in the heat dissipation metal film;
Filling the opening with droplets;
In the opening, the bonding surface of the laser crystal and the bonding end surface of the wavelength conversion element are overlapped via the droplet, and the laser crystal and the wavelength conversion element are autonomously combined by the surface tension of the droplet. Aligning with:
Bonding the laser crystal and the wavelength conversion element;
And disposing a heat sink so as to be in contact with the heat dissipating metal film.   16. The method of manufacturing a laser module according to claim 15, wherein the laser crystal and the wavelength conversion element are autonomously aligned after bonding the laser crystal and the heat sink.   The opening of the heat dissipation metal film is formed by a photolithography technique using a photoresist film, and the laser crystal and the wavelength conversion element are autonomously moved with the photoresist film remaining on the heat dissipation metal film. The method of manufacturing a laser module according to claim 15 or 16, wherein alignment is performed.   18. The shape according to claim 15, wherein the shape of the opening of the heat dissipation metal film is a rectangular shape having a ratio of long side to short side of 5: 4 to 5: 3. Laser module manufacturing method.   The method of manufacturing a laser module according to claim 18, wherein a direction in which the long side extends is parallel to a c-axis direction of the laser crystal.   20. The gap according to claim 15, wherein a gap between a bonding end face of the wavelength conversion element that is bonded to the laser crystal and the opening of the heat dissipation metal film is 0.2 mm or more. Laser module manufacturing method.

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