JP2000047276A - Semiconductor laser excited solid state shg laser device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make it possible to enhance the conveyor efficiency to second harmonic by disposing a beam shaping means into a laser resonator, thereby making the beam diameter of a laser basic wave relatively smaller in diameter. SOLUTION: The laser resonator 8 is formed of the end face of a laser crystal 4 and a laser output mirror 7. A beam shaping element 5 as the beam shaping means and a nonlinear optical crystal 6 are arranged in the respective positions where the spacings with the end face in the resonator of the laser crystal 4 attain, for example, 1 mm and 4 mm. The beam shaping element 5 is an element formed with a curvature shape on an optical substrate 5a and a cylindrical lens shape is formed on the quartz substrate surface. Both end faces thereof are so set as to be high in the transmittance to the wavelengths of the laser basic wave and the second harmonic. Such beam shaping element 5 is constituted as the two-dimensional shaping element for shaping only the one direction of the two directions orthogonal with the progressing direction of the laser beam.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a semiconductor laser-excited solid-state laser device applicable to a writing light source for an optical pickup or a laser printer, an optical measurement light source, an excitation light source for nonlinear wavelength conversion, and the like. The present invention relates to a semiconductor laser-excited solid-state SHG laser device in which a nonlinear optical crystal is disposed inside the laser resonator and can generate and output SHG (second harmonic).

[0002]

2. Description of the Related Art In recent years, research and development and commercialization of a semiconductor laser pumped solid-state laser device have been actively pursued with a reduction in the price of a high-power semiconductor laser. Semiconductor laser-pumped solid-state laser devices are extremely efficient because of the narrower spectral width of the pumping light source compared to conventional lamp pumping, and the semiconductor laser, which is the pumping light source, is smaller, resulting in smaller size and higher efficiency. It is a laser that is suitable for laser processing. Further, the semiconductor laser pumped solid-state laser is characterized by not only being capable of continuous oscillation at room temperature with high output and laser oscillation of high quality beam, but also being extremely excellent in energy storage and frequency stability. Therefore, it is expected to be a small, highly efficient and high quality laser light source.

[0003] Also, research and development and commercialization of a wavelength conversion technology using such a solid-state laser and a nonlinear optical crystal have been actively pursued. In particular, since the second harmonic generation of the solid-state laser fundamental wave can convert only the wavelength to half without deteriorating the good beam characteristics of the solid-state laser fundamental wave, it can be used as a visible light source such as blue and green in the future. It is expected as an excitation light source for ultraviolet light sources by wave generation, and research and product development are being actively conducted.

[0004] The applications of these laser light sources are diverse, such as processing, measurement, and communication. Light sources such as a laser printer light source and an optical pickup light source aim at stability as a light source and low-power driving. Along with higher efficiency, higher quality such as transverse mode quality is desired. In addition, with regard to commercialization of these laser light sources, cost reduction by reducing device production costs, component costs, and the like is also desired. That is, a high-efficiency, high-quality, and low-cost laser light source is expected as a commercial product.
For this reason, various inventions and researches have been made so far, and in particular, improvement of the transverse mode quality and efficiency are very important items when used.

A laser diode pumped solid-state laser disclosed in Japanese Patent Application Laid-Open No. Hei 6-334245 has been proposed to improve the efficiency. This was invented for the purpose of providing a laser device with good luminous efficiency by matching the shape of the excitation light beam of the semiconductor laser pumped solid-state laser device with the shape of the resonator mode of the solid-state laser optical resonator. Thus, the mode matching is improved by giving a curvature to the shape of the laser crystal inside the resonator. More specifically, as shown in FIG. 6, in a laser diode pumped solid-state laser of an end face pumping type using a laser beam from a laser diode 100, a solid-state laser medium (for example, a YAG crystal) 101 has a plano-convex cylindrical shape. The plane is used as an excitation light incident surface, and the cylindrical convex surface is arranged in the solid-state laser optical resonator 102. 103 is a collimating lens, 104 is a focusing lens, 10
5 is an output mirror. As a result, oscillation with good mode matching becomes possible.

Further, as an invention for improving the efficiency and improving the quality of the transverse beam by devising the pumping and condensing optical system, for example, a laser beam for an LD-pumped solid-state laser device disclosed in Japanese Patent Application Laid-Open No. 6-347609 has been proposed. There is an optical lens. This is a modification of the excitation focusing optical system that focuses the semiconductor laser.
The configuration is, as shown in FIG.
The laser beam from the semiconductor laser 111 is subjected to curvature processing only in one direction orthogonal to the optical axis 112 on the end face on the laser light incident side, thereby reducing the astigmatism of the laser light from the semiconductor laser 111, so that the shape of the excitation beam is substantially true. By increasing the circularity and the excitation efficiency, the efficiency is improved. In addition, high quality of the horizontal mode can be expected.

Further, as an invention for improving the transverse mode quality of a solid-state laser light source, for example, Japanese Patent Application Laid-Open No. 8-181 is disclosed.
There is a laser-diode-pumped solid-state laser disclosed in JP-A-369-369. This is because, as shown in FIG. 8, the excitation light 121 emitted from the semiconductor laser 120 is applied to the rod lens 122 or the like in order to prevent the transverse mode of the solid-state laser oscillation beam from becoming elliptical or higher order. The light is condensed by a condensing optical system.
The laser beam is converged in the laser crystal 123 so that the beam diameter becomes smaller than that of the solid-state laser beam 124 at any position within the laser crystal 123. 125 is a resonator mirror, 1
26 is a screen. This prevents the laser lateral mode from deteriorating due to the thermal lens effect or the like, and achieves a stable lateral mode.

[0008]

SUMMARY OF THE INVENTION However, Japanese Patent Laid-Open No.
In the case of the structure disclosed in Japanese Patent No. 334245, it is necessary to narrow the excitation beam to a small diameter in view of efficiency. Also,
If the laser crystal has a radius of curvature,
The cost is high.

In the case of the structure disclosed in Japanese Patent Application Laid-Open No. 6-347609, it is difficult to perform the curvature processing on the end face of the GRIN lens 110, and there is a problem in mass productivity and workability, resulting in an increase in cost.

In the structure disclosed in Japanese Patent Application Laid-Open No. 8-181369, high efficiency is achieved in the case of laser fundamental wave output. However, a nonlinear optical crystal is arranged in a resonator to reduce the second harmonic output. In the case of output, the beam diameter inside the resonator is determined by the configuration of the resonator, so that it is difficult to further improve the efficiency of the SHG output.

As described above, in the case of the conventional structure, the second harmonic output can be output with a simple configuration, and the semiconductor laser pumped solid-state S having high transverse mode quality and high efficiency can be obtained.
The HG laser device has not been completed yet, and its development is desired.

Accordingly, an object of the present invention is to provide a semiconductor laser pumped solid-state SHG laser device capable of outputting a second harmonic with high efficiency.

It is another object of the present invention to provide a semiconductor laser-excited solid-state SHG laser device capable of improving the quality of a transverse mode of a laser beam and improving the efficiency.

It is another object of the present invention to provide a semiconductor laser-pumped solid-state SHG laser device capable of simplifying a beam shaping element.

A further object of the present invention is to provide a semiconductor laser-excited solid state SHG laser device which can simplify the laser device assembling process and the alignment process and reduce the cost.

In addition, another object of the present invention is to provide a semiconductor laser pumped solid-state SHG laser device capable of reducing the number of parts.

[0017]

According to the first aspect of the present invention,
Laser crystal, a laser resonator for resonating laser light, a semiconductor laser for exciting the laser crystal, and
In a semiconductor laser-excited solid-state SHG laser device having a nonlinear optical crystal for generating a second harmonic in the laser resonator, a beam shaping means is provided inside the laser resonator.

Therefore, when the excitation light emitted from the semiconductor laser is made incident on the laser crystal, ions added to the laser crystal are excited, and fluorescence of a certain wavelength is emitted. Here, as the intensity of the excitation laser light increases, the intensity of the fluorescence increases, and the laser resonator starts to induce the laser. As the intensity of the excitation laser light further increases, laser oscillation starts. At this time, the reflectivity of the laser output mirror is higher than the fundamental
By setting the lower harmonics, the second harmonic converted by the nonlinear optical crystal arranged in the laser resonator can be efficiently extracted. Here, by arranging the beam shaping means in the laser resonator, the beam diameter of the laser beam fundamental wave in the nonlinear optical crystal can be reduced as compared with the case where the beam shaping means is not arranged. Thereby, the conversion efficiency from the laser fundamental wave to the second harmonic can be increased. Thus, by providing the beam shaping means inside the laser resonator, the beam diameter of the laser fundamental wave inside the laser resonator can be relatively reduced, and the conversion efficiency to the second harmonic can be increased. Can be
It is also possible to reduce the ellipticity of the beam,
The transverse mode quality can be improved, and a semiconductor laser-pumped solid-state SHG laser device with high efficiency and improved transverse mode quality can be provided.

According to a second aspect of the present invention, in the semiconductor laser-excited solid-state SHG laser device according to the first aspect, the beam shaping means is arranged so as to be orthogonal to the traveling direction of the laser beam.
This is a two-dimensional shaping element for shaping only one of the directions. According to a third aspect of the present invention, in the semiconductor laser-pumped solid-state SHG laser device according to the first aspect, the beam shaping means is a three-dimensional shaping element for shaping two directions orthogonal to the traveling direction of the laser beam. Therefore, an example of the configuration of the beam shaping unit becomes clear. In the case of the two-dimensional shaping element according to the second aspect, the beam diameter of the laser fundamental wave in the nonlinear optical crystal becomes closer to a circle, and a high-quality transverse mode can be generated. According to the shaping element, the beam diameter can be further reduced, and the efficiency can be further improved and the transverse mode quality can be improved.

According to a fourth aspect of the present invention, there is provided a semiconductor laser-excited solid state SHG laser device according to the second or third aspect,
The shaping element is an element in which a curvature shape having a beam shaping function is formed on an optical substrate. Therefore, the shaping element can be simplified, and the cost can be reduced.

According to a fifth aspect of the present invention, there is provided a semiconductor laser-excited solid state SHG laser device according to the second or third aspect,
The shaping element is formed of an optical material having high transmittance with respect to a laser fundamental wave and a second harmonic. Therefore,
The loss inside the resonator can be reduced, and the efficiency of the device can be further improved.

The invention according to claim 6 is the invention according to claims 1 to 5
In the semiconductor laser-excited solid-state SHG laser device according to any one of the above, the shaping element is fixed to and integrated with the laser crystal. Therefore, assembling the apparatus, the number of alignment steps can be reduced and simplified, and the cost can be reduced.

[0023] The invention according to claim 7 is the invention according to claims 1 to 5.
In the semiconductor laser-pumped solid-state SHG laser device according to any one of the above, the shaping element is fixed to and integrated with the nonlinear optical crystal. Therefore, assembling the apparatus, the number of alignment steps can be reduced and simplified, and the cost can be reduced.

[0024] The invention according to claim 8 provides the invention according to claims 1 to 5.
In the semiconductor laser-pumped solid-state SHG laser device according to any one of the above, the shaping element is formed integrally with a part of the nonlinear optical crystal. Therefore, assembling the apparatus, the number of alignment steps can be reduced and simplified, the cost can be reduced, and the number of parts can be reduced.

[0025]

FIG. 1 shows a first embodiment of the present invention.
It will be described based on. FIG. 1 is a configuration diagram showing a semiconductor laser-pumped solid-state SHG laser 1 of the present embodiment,
Is a plan view, and (b) is a side view thereof. This solid-state laser SHG laser device 1 includes a semiconductor laser 2, a laser light focusing optical system 3, a laser crystal 4, and a beam shaping element 5.
And a nonlinear optical crystal 6 and a laser output mirror 7 are sequentially arranged on the optical axis. Here, the laser resonator 8 is formed by the end face of the laser crystal 4 and the laser output mirror 7, and the resonator length is, for example, 25.
mm. The beam shaping element 5 as a beam shaping means is arranged at an interval of 1 mm from the cavity inner end face of the laser crystal 4, and the nonlinear optical crystal 6 has a distance of 4 mm from the cavity inner end face of the laser crystal 4. Is located in the position.

Here, each component will be described in more detail. First, the semiconductor laser 2 that excites the laser crystal 4
The one having a center wavelength of 809 nm and an output power of 1 W is used. The emission diameter of such a semiconductor laser 2 is 1 × 100 μm.

The laser crystal 4 is a YVO ₄ crystal to which Nd is added at 1.1 at%, and has a size of 3 × 3 mm and a thickness of 1 mm. Both surfaces are coated so as to enable laser oscillation, and the end face on the laser beam incident side has a high reflectance (99.99%) with respect to a wavelength of 1064 nm, which is a fundamental laser beam, and has a second harmonic. Is higher for the wavelength of 532 nm (99.9).
%), And is coated so as to have a high transmittance (99%) with respect to a wavelength of 809 nm which is excitation light. The end face on the side of the laser resonator 8 has a wavelength of 1064 nm which is a laser fundamental wave and a wavelength of 532 which is a second harmonic.
high transmittance (99.99 nm at 1064 nm).
%, 99.9% at 532 nm).

As the nonlinear optical crystal 6, a KTP crystal is used. The size is 3 × 3 mm, and the thickness in the optical axis direction is 5 mm. The cut angle of the crystal is set to θ = 90 ° and φ = 2 so that type II phase matching can be performed with respect to a wavelength of 1064 nm which is a fundamental laser beam.
The angle is 4.4 °. Both end surfaces are coated so as to enable laser oscillation. That is,
The coating is performed so that the transmittance is high (99.9% for any wavelength) for the wavelength 1064 nm, which is the laser fundamental wave, and the wavelength 532 nm, which is the second harmonic.

The laser output mirror 7 is made of quartz and has a radius of curvature of 50 mm. On the surface inside the laser resonator 8, a wavelength of 10
The reflectivity is high (99.99%) for 64 nm,
The transmittance is high for a wavelength of 532 nm, which is a harmonic (9
5%). In addition, the output end face of the laser beam has a high transmittance with respect to the wavelength 532 nm (9) so that the second harmonic can be taken out at high efficiency.
(9.99%).

The beam shaping element 5 is an element having a curvature shape formed on an optical substrate 5a.
50 mm radius of curvature on the surface of a quartz substrate (optical substrate 5a)
m cylindrical lens shape is formed. On both end surfaces, the transmittance is set to be high (99.99% at any wavelength) for the wavelength 1064 nm, which is the laser fundamental wave, and the wavelength 532 nm, which is the second harmonic. The size is cut out at 3 × 3 mm. Such a beam shaping element 5 has one of two directions orthogonal to the traveling direction of the laser beam (FIG. 1).
It is configured as a two-dimensional shaping element for shaping only the beam diameter in the laser resonator 8 when viewed from the plane direction shown in FIG.

In such a configuration, the semiconductor laser 2
The excitation light output from is collected by the condensing optical system 3 and enters the laser crystal 4. As a result, fluorescence having a central wavelength of 1064 nm from the laser crystal 4 oscillates in the laser resonator 8. Here, since the transmittance of the laser output mirror 7 is set as described above, the laser light having a wavelength of 1064 nm, which is a fundamental laser beam, is confined in the laser resonator 8 with high intensity. At this time, since the KTP crystal is arranged as the nonlinear optical crystal 6 inside the laser resonator 8, it is possible to perform conversion to the second harmonic using the high-intensity laser fundamental wave in the laser resonator 8. it can. As a result, the output of the second harmonic can be output from the laser output mirror 7 with high efficiency.

At this time, in the present embodiment, the beam shaping element 5 is arranged inside the laser resonator 8 so that the second
The efficiency of conversion to harmonics is increased, and the quality of the output beam transverse mode is improved. Accordingly, the beam diameter of the laser fundamental wave inside the laser resonator 8 can be reduced and the ellipticity can be reduced, so that the conversion efficiency can be increased and the quality of the output beam can be improved.

How to improve the efficiency and the quality of the second harmonic by the beam shaping element 5 will be described in detail. First, the laser beam emitted from the semiconductor laser 2 is an elliptical beam, which is a light source having astigmatism. When this light is condensed, it often becomes an elliptical beam as it is. Also in the present embodiment, the excitation size of the laser crystal 4 is 90 μm × 110 μm (radius). As a result, the laser fundamental wave is normally about 92 μm in the laser crystal 4 in the laser resonator 8 in the direction of FIG.
It is about 130 μm on the laser output mirror 7. On the other hand, in the direction of FIG. 1B, it is about 110 μm in the laser crystal 4 and about 155 μm on the laser output mirror 7. This allows
The output beam is an elliptical beam. At this time, considering the beam diameter of the laser fundamental wave inside the KTP crystal (nonlinear optical crystal 6), 94 μm × 112 μm to 9 μm
It is an elliptical beam of 9 μm × 118 μm (radius). Therefore, as shown in FIG. 1, when the beam shaping element 5 is disposed inside the laser resonator 8, the beam diameter of the laser fundamental wave inside the KTP crystal (nonlinear optical crystal 6) becomes 9
It becomes an elliptical beam of 4 μm × 105 μm to 99 μm × 102 μm (radius). This not only reduces the ellipticity but also increases the intensity of the laser fundamental wave.
The conversion efficiency to the second harmonic increases. This increases the second harmonic output, as described above, and
The beam transverse mode quality is also improved.

A second embodiment of the present invention will be described with reference to FIG. The same parts as those shown in FIG. 1 are denoted by the same reference numerals, and description thereof is omitted (the same applies to the following embodiments). 2A and 2B are configuration diagrams showing the semiconductor laser-excited solid state SHG laser 11 of the present embodiment, wherein FIG. 2A is a plan view and FIG. 2B is a side view thereof. In the present embodiment,
Instead of the beam shaping element 5 formed as a two-dimensional shaping element, a beam shaping element 12 formed as a three-dimensional shaping element is used as a beam shaping unit.

The beam shaping element 12 includes an optical substrate 12
This is an element having a curvature shape formed on a, and here, a toric lens shape having a curvature radius of 80 mm × 35 mm is formed on both surfaces of a quartz substrate (optical substrate 5a) having a thickness of 0.5 mm. At both end surfaces, the transmittance is high for a wavelength of 1064 nm, which is a laser fundamental wave, and a wavelength of 532 nm, which is a second harmonic (99.99 nm for any wavelength).
%). The size is 3
It is cut out at × 3 mm. Such a beam shaping element 12 is arranged as a three-dimensional shaping element that is arranged so that the direction having a large radius of curvature is the direction of FIG. 2A and that shapes the laser beam in two directions orthogonal to the traveling direction of the laser beam. ing.

Even with such a configuration, basically,
As in the case of the first embodiment, by arranging the beam shaping element 12 inside the laser resonator 8, the conversion efficiency to the second harmonic is increased, and the high quality of the output beam transverse mode is obtained. Is being planned. Accordingly, the beam diameter of the laser fundamental wave inside the laser resonator 8 can be reduced and the ellipticity can be reduced, so that the conversion efficiency can be increased and the quality of the output beam can be improved. In particular, according to the present embodiment, as shown in FIG. 2, when the beam shaping element 12 is provided inside the laser resonator 8, the beam of the laser fundamental wave inside the KTP crystal (nonlinear optical crystal 6) The diameter is 9
It becomes an elliptical beam of 0 μm × 103 μm to 90 μm × 95 μm (radius). As a result, not only the ellipticity is further reduced, but also the intensity of the laser fundamental wave is further increased, so that the conversion efficiency to the second harmonic is increased.
This increases the second harmonic output, as described above,
In addition, the beam transverse mode quality is also improved.

A third embodiment of the present invention will be described with reference to FIG. 3A and 3B are configuration diagrams showing the semiconductor laser pumped solid-state SHG laser 21 of the present embodiment, wherein FIG. 3A is a plan view and FIG. 3B is a side view thereof. In the present embodiment, 3
A beam shaping element 12 formed as a dimensional shaping element is integrated adjacent to an end face of the laser crystal 4 inside the resonator. That is, an adhesive guide 12b is formed at the end of the beam shaping element 12 having the shape shown in FIG. That is, a flat portion higher than the top portion of the lens shape is formed,
The beam shaping element 12 can be arranged without contacting the laser crystal 4.

Even with such a configuration, basically,
As in the first and second embodiments, the laser resonator 8
By disposing the beam shaping element 12 inside the
The efficiency of conversion to harmonics is increased, and the quality of the output beam transverse mode is improved. Accordingly, the beam diameter of the laser fundamental wave inside the laser resonator 8 can be reduced and the ellipticity can be reduced, so that the conversion efficiency can be increased and the quality of the output beam can be improved. In particular, according to the present embodiment, as shown in FIG.
When the beam shaping element 12 is provided inside, the beam diameter of the laser fundamental wave inside the KTP crystal (nonlinear optical crystal 6) becomes an elliptical beam of 89 μm × 100 μm to 89 μm × 92 μm (radius). As a result, not only the ellipticity is further reduced, but also the intensity of the laser fundamental wave is further increased, so that the conversion efficiency to the second harmonic is increased. As a result, as described above, the output of the second harmonic is increased, the quality of the transverse beam mode is improved, and the alignment process can be reduced in assembling the apparatus.
It can be simplified.

A fourth embodiment of the present invention will be described with reference to FIG. 4A and 4B are configuration diagrams showing a semiconductor laser-excited solid-state SHG laser 31 of the present embodiment, wherein FIG. 4A is a plan view and FIG. 4B is a side view thereof. In the present embodiment, 3
A beam shaping element 12 formed as a dimension shaping element is integrated adjacent to an end face of the nonlinear optical crystal 6 on the laser crystal 4 side. That is, an adhesive guide 12c is formed at the end of the beam shaping element 12 having the shape shown in FIG. In other words, a flat portion higher than the top of the lens shape is formed,
Thereby, the beam shaping element 12 can be arranged without contacting the nonlinear optical crystal 6.

Even with such a configuration, basically,
As in the first, second, and third embodiments, by arranging the beam shaping element 12 inside the laser resonator 8, the conversion efficiency to the second harmonic is increased, and the output beam width is increased. The mode has been improved in quality. This allows
Since the beam diameter of the laser fundamental wave inside the laser resonator 8 can be reduced and the ellipticity can be reduced, the conversion efficiency can be increased and the quality of the output beam can be improved. In particular,
According to the present embodiment, as shown in FIG. 4, when the beam shaping element 12 is disposed inside the laser resonator 8, KT
The beam diameter of the laser fundamental wave inside the P crystal (nonlinear optical crystal 6) is 93 μm × 111 μm to 93 μm × 102 μ.
It becomes an elliptical beam of m (radius). As a result, not only the ellipticity decreases, but also the intensity of the laser fundamental wave increases, so that the conversion efficiency to the second harmonic increases. As a result, as described above, the output of the second harmonic is increased, the beam transverse mode quality is improved, and the alignment process can be reduced and simplified in assembling the apparatus.

A fifth embodiment of the present invention will be described with reference to FIG. 5A and 5B are configuration diagrams showing a semiconductor laser-excited solid state SHG laser 41 of the present embodiment, wherein FIG. 5A is a plan view and FIG. 5B is a side view thereof. In the present embodiment, a beam shaping element 42 is integrally formed on the end face of the nonlinear optical crystal 6 on the side of the laser crystal 4. That is, a cylindrical lens shape having a radius of curvature of 70 mm is formed on the end face of the nonlinear optical crystal 6. In this case, it is arranged such that there is a curvature surface when viewed in the direction of FIG.

Even with such a configuration, basically,
As in the case of the above-described embodiment, by arranging the nonlinear optical element 6 in which the beam shaping element 42 is integrated inside the laser resonator 8, the conversion efficiency to the second harmonic is increased, and In this case, the quality of the output beam transverse mode is improved. Accordingly, the beam diameter of the laser fundamental wave inside the laser resonator 8 can be reduced and the ellipticity can be reduced, so that the conversion efficiency can be increased and the quality of the output beam can be improved. In particular, according to the present embodiment, when the beam shaping element 42 integrated with the nonlinear optical crystal 6 is disposed inside the laser resonator 8 as shown in FIG.
The beam diameter of the laser fundamental wave inside the P crystal (non-linear optical crystal 6) is 89 μm × 111 μm to 99 μm × 110 μm.
It becomes an elliptical beam of m (radius). As a result, not only the ellipticity decreases, but also the intensity of the laser fundamental wave increases, so that the conversion efficiency to the second harmonic increases. As a result, as described above, the output of the second harmonic is increased, the beam transverse mode quality is improved, and the alignment process can be reduced and simplified in assembling the apparatus.

In each of these embodiments, the material of the beam shaping element has a high transmittance with respect to a wavelength of 1064 nm, which is a laser fundamental wave, and a wavelength of 532 nm, which is a second harmonic, such as sapphire and synthetic quartz. A material may be used. At that time, it is necessary to change the value of the created radius of curvature according to the refractive index. Further, in each of these embodiments, the end face excitation configuration example has been described.
The same can be applied to the side excitation configuration. Furthermore, the laser crystal has been described as an example of a four-level Nd: YVO ₄ crystal, but the present invention is not particularly limited thereto.
Four-level Nd: YAG or Nd: LSB, or a three-level laser crystal (for example, Yb: YAG) can be applied. Further, as the nonlinear optical crystal, any material that can be phase-matched, such as a KTP crystal or a KN crystal, can be applied.

[0044]

According to the first aspect of the present invention, since the beam shaping means is provided inside the laser resonator, the beam diameter of the laser fundamental wave inside the laser resonator can be relatively reduced. A semiconductor that can increase the conversion efficiency to the second harmonic, can reduce the ellipticity of the beam, can improve the transverse mode quality, and has high efficiency and improved transverse mode quality. A laser-excited solid state SHG laser device can be provided.

According to the second and third aspects of the present invention, it is possible to clarify an example of the configuration of the beam shaping means for obtaining the effect of the first aspect of the present invention. In this case, the beam diameter of the laser fundamental wave in the nonlinear optical crystal becomes closer to a circle, and a high-quality transverse mode can be generated. In particular, according to the three-dimensional shaping element of claim 3, the beam diameter is reduced. The diameter can be further reduced, and the efficiency can be further improved and the transverse mode quality can be improved.

According to the fourth aspect of the present invention, since the shaping element is an element in which a curvature shape having a beam shaping function is formed on the optical substrate, the shaping element can be simplified, and the cost can be reduced. Can be achieved.

According to the fifth aspect of the present invention, since the shaping element is formed of an optical material having high transmittance with respect to the laser fundamental wave and the second harmonic, the loss inside the resonator can be reduced. It is possible to achieve higher efficiency of the apparatus.

According to the sixth aspect of the present invention, since the shaping element is fixed to and integrated with the laser crystal, the assembly process can be simplified by reducing the number of alignment steps, and the cost can be reduced. Can be.

According to the seventh aspect of the present invention, since the shaping element is fixed to and integrated with the nonlinear optical crystal, the assembling of the apparatus can be simplified by reducing the number of alignment steps, and the cost can be reduced. be able to.

According to the eighth aspect of the present invention, since the shaping element is integrally formed with a part of the nonlinear optical crystal, the assembly process can be simplified by reducing the number of alignment steps and reducing the cost. Besides, the number of parts can be reduced.

[Brief description of the drawings]

FIGS. 1A and 1B show a semiconductor laser-excited solid state SHG laser according to a first embodiment of the present invention, wherein FIG. 1A is a plan view and FIG.

FIGS. 2A and 2B show a semiconductor laser-pumped solid-state SHG laser according to a second embodiment of the present invention, wherein FIG. 2A is a plan view and FIG.

3A and 3B show a semiconductor laser-pumped solid-state SHG laser according to a third embodiment of the present invention, wherein FIG. 3A is a plan view and FIG. 3B is a side view thereof.

4A and 4B show a semiconductor laser-pumped solid-state SHG laser according to a fourth embodiment of the present invention, wherein FIG. 4A is a plan view and FIG. 4B is a side view thereof.

5A and 5B show a semiconductor laser-pumped solid state SHG laser according to a fifth embodiment of the present invention, wherein FIG. 5A is a plan view and FIG. 5B is a side view thereof.

FIG. 6 is a configuration diagram showing a first conventional example.

7A and 7B show a second conventional example, in which FIG. 7A is a plan view and FIG.
Is a side view thereof.

FIG. 8 is a configuration diagram showing a second conventional example.

[Explanation of symbols]

 Reference Signs List 2 semiconductor laser 4 laser crystal 5 beam shaping means 5a optical substrate 6 nonlinear optical crystal 8 laser resonator 12 beam shaping means 12a optical substrate 42 beam shaping means

Claims (8)

[Claims] A laser crystal, a laser resonator for resonating a laser beam, a semiconductor laser for exciting the laser crystal, and a nonlinear optical crystal for generating a second harmonic in the laser resonator. A solid-state SHG laser device excited by a semiconductor laser, comprising a beam shaping means inside the laser resonator. 2. The semiconductor laser-excited solid according to claim 1, wherein said beam shaping means is a two-dimensional shaping element for shaping only one of two directions orthogonal to the traveling direction of the laser beam. SHG laser device. 3. The semiconductor laser-excited solid-state SHG laser device according to claim 1, wherein said beam shaping means is a three-dimensional shaping element for shaping two directions orthogonal to a traveling direction of a laser beam. 4. The semiconductor laser-excited solid-state SHG laser device according to claim 2, wherein said shaping element is an element in which a curvature shape having a beam shaping function is formed on an optical substrate. 5. The laser device according to claim 1, wherein the shaping element includes a laser fundamental wave and a second fundamental wave.
4. The solid state laser SHG laser device according to claim 2, wherein the semiconductor material is formed of an optical material having high transmittance with respect to harmonics. 6. The semiconductor laser-excited solid-state SHG laser device according to claim 1, wherein the shaping element is fixed to and integrated with the laser crystal. 7. The device according to claim 1, wherein the shaping element is fixed to and integrated with the nonlinear optical crystal.
Semiconductor laser-excited solid SH according to any one of claims 1 to 5,
G laser device. 8. The device according to claim 1, wherein the shaping element is formed integrally with a part of the nonlinear optical crystal.
Semiconductor laser-excited solid SH according to any one of claims 1 to 5,
G laser device.