JP2006186071A - Photoexcitation solid state laser device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To stably obtain harmonic output without being influenced by temperatures or excitation power by preventing the fluctuation of beam condition due to the interference of a harmonic component with a different phase. <P>SOLUTION: In the photoexcitation solid state laser device 20, a pair of reflecting mirrors 24, 25, consisting of an incidental side and an outgoing side, which are pinching a solid state laser medium 22 and a non-linear optical element 23, are formed respectively so as to be highly reflective with respect to a base wave L2, and so as to prevent reflection with respect to harmonics L3, L4 whereby interference can be prevented between mutual harmonic components in an optical resonator. At the same time, the light emitting surface 21a of a photoexcitation light source (semiconductor laser device) 21 is formed so as to be un-parallel to the mirror plane of an incidental side reflecting mirror 24, whereby the optical axis of the reflecting light is provided with an angle with respect to the optical axis of the optical resonator 26, thereby suppressing the mutual interference between harmonic components L3, L4 in the optical resonator 26 when the outgoing harmonic laser beam L4 from the incidental side reflecting mirror 24 is reflected by the light emitting surface 21a of the photoexcitation light source 21. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an optically pumped solid-state laser device that makes a fundamental laser beam generated in a solid-state laser medium enter a nonlinear optical element and generate a harmonic laser beam having a wavelength that is a multiple of the fundamental laser beam.

  2. Description of the Related Art Conventionally, wavelength conversion solid-state laser devices that generate laser light having a wavelength multiplied by a fundamental wavelength using a nonlinear optical element have been used in various fields as solid-state laser devices. In this type of solid-state laser device, an optically pumped solid-state laser device using a semiconductor laser as a pumping source for pumping a solid-state laser medium is widely used.

In order to improve the frequency conversion efficiency of laser light, this type of optically pumped solid-state laser device often employs an internal resonance type structure in which a solid-state laser medium and a nonlinear optical element are arranged between a pair of reflecting mirrors. . As the solid-state laser medium, a crystal element such as Nd: YAG or Nd: YVO ₄ is used, and as the nonlinear optical element, a crystal element such as KTP (KTiOPO ₄ ) or BBO (β-BaB ₂ O ₄ ) is used. It is used. A combination crystal in which the solid laser medium and the nonlinear optical element are integrated by bonding or the like is also used (for example, see Patent Document 1 below).

  FIG. 10 shows a schematic configuration of a conventional optically pumped solid-state laser device 10. This conventional optically pumped solid-state laser device 10 includes a semiconductor laser 1 that generates laser light L1 having a wavelength of 808 nm as a pumping source, a solid-state laser medium 2 that generates fundamental laser light L2 having a wavelength of 1064 nm, and a green harmonic having a wavelength of 532 nm. The nonlinear optical element 3 that generates the laser light L3, the planar incident-side reflecting mirror 4 disposed on the light incident side end face of the solid-state laser medium 2, and the planar shape disposed on the light emitting side end face of the nonlinear optical element 3 The output side reflecting mirror 5 is provided.

  The solid-state laser medium 2 and the nonlinear optical element 3 are formed as a combination crystal 7 integrated with each other by bonding or the like, and the combination crystal 7 and the pair of reflecting mirrors 4 and 5 constitute an optical resonator 6. Yes. The optical axes of the semiconductor laser 1 and the optical resonator 6 are arranged coaxially with each other.

On the mirror surface (reflecting surface) of the incident-side reflecting mirror 4, the laser light emitted from the semiconductor laser 1, that is, excitation light (pumping light) is prevented from being reflected, and the fundamental laser light generated in the solid-state laser medium 2 and nonlinearity are prevented. A coating film that is highly reflective to the harmonic laser light generated by the optical element 3 is formed.
On the other hand, a coating film that is highly reflective with respect to the fundamental laser beam and that prevents reflection with respect to the harmonic laser beam is formed on the mirror surface of the emission-side reflecting mirror 5.

  FIG. 11 is a diagram schematically illustrating a change in the wavelength of light inside the optical resonator 6 of the conventional optically pumped solid-state laser device 10 configured as described above. When the excitation light L1 emitted from the semiconductor laser 1 is incident on the solid-state laser medium 2, a fundamental wave is generated in the solid-state laser medium 2, and this fundamental wave is generated between the incident-side reflecting mirror 4 and the emitting-side reflecting mirror 5. The oscillation laser beam L2 of the fundamental wave is obtained inside the optical resonator 6 by oscillating at. The fundamental oscillation laser beam L2 passes through the nonlinear optical element 3 so that a part of the wavelength is converted into a harmonic laser beam L3 and then optically resonated through the output-side reflecting mirror 5. It is emitted to the outside of the vessel 6.

  On the other hand, the component of the fundamental laser light L2 incident on the nonlinear optical element 3 from the solid laser medium 2 side that has not been wavelength-converted by the nonlinear optical element 3 is reflected by the output-side reflecting mirror 5 and then again the nonlinear optical element 3. Pass through. At this time, a part of the fundamental wave laser light is wavelength-converted by the nonlinear optical element 3 to be a harmonic laser light component L4. The harmonic laser beam component L4 is reflected by the incident-side reflecting mirror 4 through the solid-state laser medium 2, and the reflected harmonic component L5 passes through the solid-state laser medium 2, the nonlinear optical element 3, and the emitting-side reflecting mirror 5. And is emitted to the outside of the optical resonator 6.

JP 2004-281932 A Japanese Patent Laid-Open No. 7-106682

  In the conventional optically pumped solid-state laser device 10, as described above, of the fundamental laser beam L2 that travels from the exit-side reflecting mirror 5 side to the incident-side reflecting mirror 4 side, the harmonic converted in wavelength by the nonlinear optical element 3 is used. The wave component L4 is reflected by the incident-side reflecting mirror 4, and the reflected light L5 is emitted outside the optical resonator 6 through the emitting-side reflecting mirror 5. This is because the purpose is to obtain the harmonic laser light with high output by combining the L2 component and the L5 component of the harmonic laser light generated inside the optical resonator 6 and emitting the combined light.

  However, since the phase of the harmonic component L5 changes when it passes through the solid laser medium 2 that is a birefringent material, it is not easy to make the phases completely coincide with each other. In addition, the phase becomes inconsistent due to a change in the refractive index of the solid-state laser medium 2 due to a change in temperature or pumping power, and the output of the harmonic laser beam is likely to change. Furthermore, the polarization state changes due to the interference of light with different phases, and the beam transverse mode (spatial intensity distribution or phase distribution of the laser beam) becomes unstable, resulting in the generation of multi-beams and changes in beam size. There is a problem of getting up.

  On the other hand, in Patent Document 2 described above, in an optically pumped solid-state laser device having a semiconductor laser, a solid-state laser medium, and a nonlinear optical element that are coaxially arranged, the incident-side reflecting mirror is made anti-reflective with respect to harmonics. A configuration for solving the above problem is disclosed.

  However, even with the configuration of Patent Document 2, it is difficult to achieve a fundamental solution to the problems described above.

  That is, since light emitted from a semiconductor laser (laser diode) generally has a large divergence angle, light having a wavelength of 808 nm emitted from the semiconductor laser has an increased light diameter until it reaches the solid-state laser medium. Energy density will decrease. For this reason, it is important to improve the efficiency of exciting the light with a wavelength of 1064 nm in the solid-state laser medium by bringing the light emitting surface of the semiconductor laser and the incident side reflecting mirror of the optical resonator as close as possible.

  However, when the light emitting surface of the semiconductor laser is brought close to and opposite to the incident side reflecting mirror of the optical resonator, the harmonics transmitted through the incident side reflecting mirror are reflected by the light emitting surface of the semiconductor laser, and the reflected harmonics are incident on the incident side. The light enters the optical resonator through the reflecting mirror. As a result, harmonic components having different phases exist in the optical resonator, and the same problem as described above occurs.

  The present invention has been made in view of the above-described problems, and prevents the fluctuation of the beam state due to the interference of the harmonic components having different phases, and the optically pumped solid-state laser capable of stably obtaining the harmonic output without being affected by the temperature and the pumping power. It is an object to provide an apparatus.

  In solving the above-described problems, the optically pumped solid-state laser device of the present invention has a pair of reflecting mirrors on the incident side and the output side sandwiching the solid-state laser medium and the nonlinear optical element. Reflection is performed to prevent reflection of harmonics, and the light emitting surface of the excitation light source is not parallel to the mirror surface of the incident-side reflecting mirror.

  In the optically pumped solid-state laser device of the present invention having such a configuration, the solid-state laser medium, the nonlinear optical element, and the pair of reflecting mirrors constitute an optical resonator. When the excitation light emitted from the excitation light source enters the solid-state laser medium, a fundamental wave is generated in the solid-state laser medium, and the fundamental wave oscillates inside the optical resonator, thereby obtaining a fundamental-wave laser beam. The fundamental laser beam is partly wavelength-converted by passing through the non-linear optical element to become a harmonic laser beam, and is emitted to the outside of the optical resonator through the reflecting mirror.

  In the present invention, the pair of reflecting mirrors prevent reflection of harmonics, so that harmonic laser light generated inside the optical resonator is emitted to the outside of the optical resonator via these reflecting mirrors. . Thereby, since interference between harmonic components inside the optical resonator can be prevented, it is possible to obtain a stable harmonic laser beam in a beam transverse mode that is not affected by temperature and pumping power.

  In the present invention, since the light emitting surface of the excitation light source is not parallel to the mirror surface of the incident side reflecting mirror, the harmonic laser beam emitted from the incident side reflecting mirror is reflected by the light emitting surface of the excitation light source. At this time, the optical axis of the reflected light has an angle with respect to the optical axis of the optical resonator. Thereby, the incidence of the harmonic component reflected by the light emitting surface of the excitation light source into the optical resonator can be suppressed, or the optical axis of the reflected light can be made different from the optical axis of the optical resonator even if it is incident. Therefore, interference with harmonic components inside the optical resonator can be suppressed, and a stable harmonic output can be maintained.

  As an example of a configuration in which the light emitting surface of the excitation light source is non-parallel to the mirror surface of the incident-side reflecting mirror, the excitation light source is arranged so that the output optical axis of the excitation light source is non-perpendicular to the mirror surface of the incident-side reflecting mirror. Arrange the light emitting surface, or arrange the excitation light source so that the emission optical axis of the excitation light source is substantially perpendicular to the mirror surface of the incident-side reflecting mirror, and place the light emission surface of the excitation light source with respect to the emission optical axis. To be non-vertical.

  The excitation light source includes a semiconductor laser element such as a laser diode chip or a package structure incorporating the same, and a light emitting surface of the semiconductor laser includes a crystal cleavage plane of the element, a light emission window of the package structure, and the like. Is applicable.

  As described above, according to the optically pumped solid-state laser device of the present invention, interference between harmonic components inside the optical resonator can be prevented, so that stable harmonics of the beam transverse mode that are not affected by temperature and pumping power are stable. Laser light can be obtained.

  Embodiments of the present invention will be described below with reference to the drawings.

(First embodiment)
FIG. 1 is a schematic configuration diagram of an optically pumped solid-state laser device 20 according to the first embodiment of the present invention. The illustrated optically pumped solid-state laser device 20 includes a semiconductor laser element 21 as a pumping light source, a solid-state laser medium 22, a nonlinear optical element 23, and a planar incident-side reflection disposed on the light incident-side end face of the solid-state laser medium 22. A mirror 24 and a planar emission-side reflecting mirror 25 disposed on the light emission-side end face of the nonlinear optical element 23 are provided.

  The semiconductor laser element 21 is composed of an element that oscillates laser light of a predetermined wavelength when a voltage is applied, for example, a gallium aluminum arsenide (GaAlAs) laser diode element (chip). In the present embodiment, a laser element that oscillates laser light L1 having a wavelength of 808 nm is used as excitation light. The oscillation laser light L1 may be continuous light or pulsed light.

  The solid-state laser medium 22 and the nonlinear optical element 23 are formed as a combination crystal 27 integrated with each other by bonding or the like. The combination crystal 27 and the pair of reflecting mirrors 24 and 25 constitute an optical resonator 26. Yes.

  The incident-side reflecting mirror 24 and the emitting-side reflecting mirror 25 are provided on the incident-side end surface of the solid-state laser medium 22 and the emitting-side end surface of the nonlinear optical crystal element 23, respectively. The reflecting mirrors 24, 25, the incident-side end face of the solid-state laser medium 22, and the exit-side end face of the nonlinear optical crystal element 23 are orthogonal to the optical axis (axial center) direction of the optical resonator 26.

  As will be described later, the optical resonator 26 generates a fundamental laser beam L2 having a wavelength of 1064 nm in the solid-state laser medium 22 when the laser beam emitted from the semiconductor laser element 21 is incident thereon. Then, the green laser lights L3 and L4 of the second harmonic (wavelength 532 nm) of the fundamental wave are generated and emitted to the outside.

In the present embodiment, Nd: YVO ₄ is used as the solid-state laser medium 22 and potassium phosphotitanate (KTiOPO ₄ ; KTP crystal) is used as the nonlinear optical element 23. In addition, Nd: YVO ₄ is used as the solid-state laser medium 22. : YAG, other materials such as BBO (β-BaB ₂ O ₄ ) can be used as the nonlinear optical element 23.

On the mirror surface (reflecting surface) of the incident-side reflecting mirror 24, there is a coating film that is highly reflective (HR) for the fundamental wave L2 and is antireflective (AR) for the excitation light L1 and the harmonic wave L4. Is formed. As the optical film having such optical characteristics, for example, a multilayer film in which a plurality of Ta ₂ O ₅ and SiO ₂ are alternately formed can be used.

On the other hand, a coating film that is highly reflective to the fundamental wave L2 and prevents reflection from the harmonic wave L3 is formed on the mirror surface of the exit-side reflecting mirror 25. As the optical film having such optical characteristics, for example, a multilayer film in which a plurality of Ta ₂ O ₅ and SiO ₂ are alternately formed can be used.

  FIG. 2 is a diagram schematically illustrating a change in the wavelength of light inside the optical resonator 26 of the optically pumped solid-state laser device 20 of the present embodiment.

  When the excitation light L1 emitted from the semiconductor laser element 21 is incident on the solid-state laser medium 22, a fundamental wave is generated in the solid-state laser medium 22, and this fundamental wave is generated between the incident-side reflecting mirror 24 and the emitting-side reflecting mirror 25. By oscillating, an oscillation laser beam L 2 having a fundamental wave is obtained inside the optical resonator 6. The fundamental-wave oscillation laser light L2 passes through the nonlinear optical element 23 and is converted into a harmonic laser light L3 by converting a part of the wavelength thereof, and then optically resonated via the output-side reflecting mirror 25. The light is emitted outside the container 26.

  On the other hand, of the fundamental laser light L2 incident on the nonlinear optical element 3 from the solid-state laser medium 22 side, the component that has not been wavelength-converted by the nonlinear optical element 23 is reflected by the exit-side reflecting mirror 25 and then again the nonlinear optical element. Pass through 23. At this time, a part of the fundamental wave laser light is wavelength-converted by the nonlinear optical crystal element 23 to become a harmonic laser light component L4. The harmonic laser beam component L4 is emitted to the outside of the optical resonator 26 through the solid-state laser medium 22 and the incident-side reflecting mirror 24.

  In the present embodiment, as described above, the reflection mirrors 24 and 25 on the incident side and the emission side have antireflection structures with respect to the harmonics L3 and L4. The wave laser beams L3 and L4 are emitted to the outside of the optical resonator 26 through the reflecting mirrors 24 and 25. Thereby, interference between the harmonic components inside the optical resonator 26 can be prevented, so that it is possible to obtain a harmonic laser beam having a stable beam transverse mode that is not affected by temperature and pumping power.

  Here, since the light emitted from the semiconductor laser element 21 has a large divergence angle, the light having a wavelength of 808 nm emitted from the semiconductor laser element 21 has an increased light diameter until it reaches the solid-state laser medium 22, and per unit area. The energy density of the will decrease. For this reason, it is important that the light emitting surface of the semiconductor laser element 21 and the incident-side reflecting mirror 24 be as close as possible to improve the efficiency of exciting light with a wavelength of 1064 nm in the solid-state laser medium 22.

  However, when the light emitting surface of the semiconductor laser element 21 is brought close to and opposed to the incident side reflecting mirror 24, the harmonic L4 transmitted through the incident side reflecting mirror 24 is reflected by the light emitting surface of the semiconductor laser element 21, and this reflected harmonic is reflected. Enters the optical resonator 26 via the incident-side reflecting mirror 24. When the optical axis of the incident harmonic coincides with the optical axis direction of the optical resonator 26, the harmonic components (L3, L4) having different phases interfere with each other inside the optical resonator 26. Beam transverse mode of output harmonic becomes unstable.

  Therefore, in the optically pumped solid-state laser device 20 of the present embodiment, the above-described problem is solved by making the light emitting surface 21a of the semiconductor laser element 21 non-parallel to the mirror surface of the incident-side reflecting mirror 24 of the optical resonator 26. I try to avoid it.

  3 and 4 are diagrams schematically showing a relative positional relationship between the semiconductor laser element 21 and the optical resonator 26 in the optically pumped solid-state laser device 20 of the present embodiment, and A is a view seen from the side surface side, B is a view from the upper surface side. In addition, the same code | symbol is attached | subjected about the part corresponding to FIG. Reference numeral 28 in the figure denotes a heat sink that supports the semiconductor laser element (laser diode) 21 on the upper surface and radiates heat generated from the semiconductor laser 21 to the outside.

  In the configuration example shown in FIG. 3, the semiconductor laser element 21 has an emission optical axis perpendicular to the light emitting surface 21a. Then, the light emitting surface (crystal cleavage surface) 21 a is in the elevation direction with respect to the mirror surface of the incident-side reflecting mirror 24 so that the outgoing optical axis of the semiconductor laser element 21 is non-perpendicular to the mirror surface of the incident-side reflecting mirror 24. It is inclined by an angle θ1 (vertical (z) direction in the figure). In this case, the inclined arrangement of the semiconductor laser element 21 can be performed integrally with the heat sink 28.

  Further, as shown in FIG. 4, the semiconductor laser element 21 has an angle θ2 in the left-right direction (vertical (y) direction in the figure) of the light emitting surface 21a of the semiconductor laser element 21 with respect to the mirror surface of the incident-side reflecting mirror 24. Alternatively, it may be inclined. In this case, the semiconductor laser element 21 can be inclined relative to the heat sink 28.

  With such a configuration, the harmonic optical axis Lb transmitted through the incident-side reflecting mirror 24 and reflected by the light emitting surface 21 a of the semiconductor laser element 21 is in the z direction with respect to the axis La of the optical resonator 26. Since the angle θ2 can be inclined in the angle θ1 or the y direction, even if the reflected light of the harmonic enters the optical resonator 26, interference with the harmonic component inside the resonator 26 is suppressed, and the output side reflection The beam transverse mode of the harmonic laser beam L3 emitted from the mirror 25 can be maintained stably.

  The magnitudes of the angles θ1 and θ2 can be set as appropriate within a range in which interference with harmonic components inside the optical resonator 26 can be suppressed. Further, the configuration examples shown in FIGS. 3 and 4 may be applied alone or in combination.

  According to the optically pumped solid state laser device 20 of the present embodiment configured as described above, the light emitting surface 21a of the semiconductor laser element 21 is made non-parallel to the mirror surface of the incident-side reflecting mirror 24. Even if the light emitting surface 21 a of 21 is arranged close to the optical resonator 26, the harmonic component emitted from the incident-side reflecting mirror 24 is reflected between the reflected light on the light emitting surface 21 a and the harmonic component in the optical resonator 26. Interference can be effectively suppressed, the excitation efficiency of the solid-state laser medium 22 can be increased, and higher output of the harmonic laser beam can be achieved.

  In the present embodiment, the solid-state laser medium 22 and the nonlinear optical element 23 are formed of a combination crystal 27 integrally coupled, and the solid-state laser medium 22 has an incident side end face and a nonlinear optical element 23 on the emission side end face. The optical resonator 26 is formed by integrally forming the incident-side reflecting mirror 24 and the emitting-side reflecting mirror 25, so that the length of the resonator can be shortened and the device can be made compact, and the entire resonator can be fixed to the device fixing portion. Therefore, the fluctuation of the resonator length due to a temperature change or the like can be suppressed, and the stable oscillation of the laser beam can be maintained.

  Next, FIG. 5A is a graph showing an example of drive current-harmonic output (IL characteristic) of the conventional optically pumped solid-state laser device 10 described with reference to FIGS. 10 and 11. As shown in the figure, the increase in the output with respect to the drive current is not constant, and the linearity is remarkably poor, such as the occurrence of kinks. This is because when the pumping light L1 emitted from the semiconductor laser element 1 is incident on the solid-state laser medium 2, the power of the solid-state laser medium 2 rises due to the power and the refractive index changes. This is because interference occurs in a state in which the phase between the harmonic component L5 reflected by the mirror 4 fluctuates violently and a portion where the light wave strengthens and a portion where the light wave weakens are generated.

  On the other hand, FIG. 5B is a graph showing an example of the drive current-harmonic output of the optically pumped solid-state laser device 20 of the present embodiment. As shown in the figure, the increase in output with respect to the drive current is substantially constant. This is because the harmonic component L3 is output as it is without being affected by interference with other high-frequency components having different phases, thereby suppressing output fluctuations.

  FIGS. 6A and 6B show results when the beam profiler observes a change in beam state depending on the temperature (18 ° C., 25 ° C.) of the conventional optically pumped solid-state laser device 10 described with reference to FIGS. When the temperature is compared at 18 ° C. and the temperature at 25 ° C., a clear difference is observed in the profile. The dark portion at the center is a portion with a higher output, but the ratio changes between the temperature 18 ° C. and the temperature 25 ° C., although the harmonic output is the same. The beam size is also changing. This is because the phase between the harmonic component L3 and the harmonic component L5 reflected by the incident-side reflecting mirror 24 changes due to the influence of temperature, and the interference state appears as fluctuations in the beam transverse mode.

  On the other hand, FIGS. 7A and 7B show the results when the beam profiler observes the change in the beam state depending on the temperature (18 ° C., 25 ° C.) of the optically pumped solid-state laser device 20 of the present embodiment. As shown in the figure, when comparing the temperature at 18 ° C. and the temperature at 25 ° C., there is no difference in the profile. This is because the high-frequency component L3 is emitted as it is without being affected by interference with other high-frequency components having different phases, so that the beam transverse mode is stabilized.

(Second Embodiment)
Next, a second embodiment of the present invention will be described. FIG. 8 is a schematic configuration diagram of an optically pumped solid-state laser device 30 according to the second embodiment of the present invention. In the figure, portions corresponding to those of the first embodiment described above are denoted by the same reference numerals, and detailed description thereof is omitted.

  In the optically pumped solid-state laser device 30 of the present embodiment, a semiconductor laser 31 having a package structure in which a semiconductor laser element 21 is built in a housing 32 is used as a pumping light source. This type of semiconductor laser 31 is disposed opposite to the incident-side reflecting mirror 24 of the optical resonator 26 with an emission window 33 formed in a part of the housing as a light emitting surface.

  In this case, since the distance from the semiconductor laser element 21 to the optical resonator 26 is larger than that in the first embodiment, the condenser lens 34 is interposed between the emission window 33 and the optical resonator 26. By doing so, the diffused laser emission light is condensed and the excitation light L1 is made incident on the solid-state laser medium 22, so that the excitation efficiency of the solid-state laser medium 22 is increased.

  Also in the present embodiment, since the incident-side reflecting mirror 24 of the optical resonator 26 has an antireflection structure for harmonics, the harmonic component L4 emitted from the incident-side reflecting mirror 24 to the outside is a semiconductor laser. In some cases, the light is reflected by the light emitting surface (outgoing window) 33 of 31 and the reflected light reenters the optical resonator 26.

  Therefore, by making the light emitting surface 33 of the semiconductor laser 31 non-parallel to the mirror surface of the incident-side reflecting mirror 24, the optical axis Lb of the harmonic component reflected by the light emitting surface 33 is changed to the optical axis La of the optical resonator 26. Is provided with a predetermined angle to suppress interference between harmonics having different phases in the resonator, thereby obtaining a harmonic laser beam L3 having a stable beam transverse mode. Thereby, the same effects as those of the first embodiment described above can be obtained. Note that the inclination angle of the light emitting surface 33 with respect to the incident-side reflecting mirror 24 may be either the horizontal direction or the vertical direction, as in the first embodiment.

(Third embodiment)
FIG. 9 shows a schematic configuration of an optically pumped solid-state laser device 40 according to the third embodiment of the present invention. In the figure, portions corresponding to those of the first embodiment described above are denoted by the same reference numerals, and detailed description thereof is omitted.

  In the present embodiment, the semiconductor laser element 21 is formed in a tapered shape so that the light emitting surface (crystal cleavage surface) 21a is a surface that is non-perpendicular to the outgoing optical axis. The light emitting surface 21 a is disposed opposite to the incident side reflecting mirror 24 so that the outgoing optical axis of the semiconductor laser element 21 is substantially perpendicular to the mirror surface of the incident side reflecting mirror 24.

  Even in such a configuration, the optical axis Lb of the harmonic component emitted from the incident-side reflecting mirror 24 and reflected by the light emitting surface 21a can be given a predetermined angle with respect to the optical axis La of the optical resonator 26. It is possible to obtain a harmonic laser beam L3 having a stable beam transverse mode by suppressing interference between harmonics having different phases in the resonator.

  As mentioned above, although each embodiment of this invention was described, of course, this invention is not limited to these, A various deformation | transformation is possible based on the technical idea of this invention.

  For example, in each of the above embodiments, the solid-state laser medium 22 and the nonlinear optical element 23 sandwiched between the pair of reflecting mirrors 24 and 25 on the incident side and the emission side are configured by the combination crystal 27 integrally joined to each other. However, the present invention is not limited to this, and the present invention can be applied to an optical resonator having a configuration in which the solid-state laser medium 22 and the nonlinear optical element 23 are spatially separated.

  The present invention also provides an optically pumped solid-state laser having a so-called APC (auto power control) function for adjusting the pumping power of a pumping light source (semiconductor laser element) based on the output intensity of the harmonic laser beam emitted from the optical resonator. Of course, it can also be applied to the apparatus.

1 is a schematic configuration diagram of an optically pumped solid-state laser device 20 according to a first embodiment of the present invention. FIG. 6 is a diagram for explaining a change in wavelength of light inside the optical resonator 26 of the optically pumped solid-state laser device 20. 4 is a schematic diagram for explaining a relative positional relationship between a semiconductor laser element 21 and an optical resonator 26 in the optically pumped solid-state laser device 20. FIG. 4 is a schematic diagram for explaining a relative positional relationship between a semiconductor laser element 21 and an optical resonator 26 in the optically pumped solid-state laser device 20. FIG. 12 is a graph showing an example of drive current-harmonic output, where A shows the conventional optically pumped solid-state laser device 10 having the structure shown in FIGS. 10 and 11, and B shows the optically pumped solid-state laser device 20 of the present invention. Yes. It is a figure which shows the result when the change of the beam state by the temperature (18 degreeC, 25 degreeC) of the conventional optical excitation solid-state laser apparatus 10 of the structure shown in FIG.10 and FIG.11 is observed with a beam profiler. It is a figure which shows the result when the change of the beam state by the temperature (18 degreeC, 25 degreeC) of the optical excitation solid-state laser apparatus 20 of this invention is observed with a beam profiler. It is a schematic block diagram of the optical excitation solid-state laser apparatus 30 by the 2nd Embodiment of this invention. It is a schematic block diagram of the optical excitation solid-state laser apparatus 30 by the 3rd Embodiment of this invention. 1 is a schematic configuration diagram of a conventional optically pumped solid-state laser device 10. FIG. It is a figure explaining the wavelength change of the light in the optical resonator 6 of the conventional optical excitation solid-state laser apparatus 10. FIG.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 20, 30, 40 ... Optical excitation solid state laser apparatus, 21 ... Semiconductor laser element (excitation light source), 21a ... Light emission surface, 22 ... Solid laser medium, 23 ... Nonlinear optical element, 24 ... Incident side reflecting mirror, 25 ... Outgoing side reflection Mirror, 26 ... Optical resonator, 27 ... Combination crystal, 28 ... Heat sink, 31 ... Semiconductor laser (excitation light source), 33 ... Exit window (light emitting surface), 34 ... Condensing lens.

Claims (6)

A solid-state laser medium that generates a fundamental wave, a nonlinear optical element that generates harmonics of the fundamental wave, and a pair of an incident side and an emission side that reciprocate light by sandwiching the solid-state laser medium and the nonlinear optical element. And an excitation light source that emits light for exciting the solid-state laser medium that is disposed opposite to the incident-side reflection mirror,
Each of the pair of reflecting mirrors is highly reflective to the fundamental wave and anti-reflective to the harmonics,
The light excitation surface of the said excitation light source is non-parallel with respect to the mirror surface of the said incident side reflective mirror. The optical excitation solid-state laser apparatus characterized by the above-mentioned. 2. The optically pumped solid-state laser device according to claim 1, wherein the excitation light source is disposed so that an output optical axis thereof is in a non-perpendicular direction with respect to a mirror surface of the incident-side reflecting mirror. The excitation light source is disposed so that its outgoing optical axis is substantially perpendicular to the mirror surface of the incident-side reflecting mirror, and
2. The optically pumped solid-state laser device according to claim 1, wherein a light emitting surface of the pumping light source is formed non-perpendicular to the emission optical axis. 2. The optically pumped solid-state laser device according to claim 1, wherein a light emitting surface of the pumping light source is a crystal cleavage plane of a semiconductor laser element. The light-excited solid-state laser device according to claim 1, wherein the light-emitting surface of the pumping light source is a light exit window of a package structure including a semiconductor laser element. The optically pumped solid-state laser device according to claim 1, wherein the solid-state laser medium and the nonlinear optical element are a combination crystal integrated with each other.