JP2000183433A - Solid-state shg laser - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a solid-stage second harmonic generation(SHG) laser capable of stabilizing an output, without receiving adverse effects due to heat generated by a laser crystal. SOLUTION: This solid-state SHG laser device 31 can stabilize output by discharging heat generated from a laser crystal 34 to the side of a nonlinear optical crystal 33 arranged in a laser resonator 36 without the use of a specific cooling wheel by using end surface exciting structure for bringing the crystal 34 into contact with the crystal 33 at extraction of a 2nd higher harmonic wave converted by the crystal 33 and making excited light generated from a laser exciting light source 32 incident from the side of the crystal 33 emit to the crystal 34.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a solid-state laser device applicable to a writing light source for an optical pickup or a laser printer, a light source for optical measurement, a light source for excitation for nonlinear wavelength conversion, and the like. The present invention relates to a solid-state SHG laser device in which a non-linear optical crystal is provided inside a vessel 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 have very high efficiency because the excitation light source has a narrower spectral width than conventional lamp pumping, and the semiconductor laser, which is the pumping light source, is also small, making it more compact and more efficient. It is a suitable laser. 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] These laser light sources are used in a wide variety of applications such as processing, measurement, and communication. However, light sources such as a laser printer light source and an optical pickup light source are more stable, have higher efficiency, and have better lateral mode quality. There is a demand for higher quality. In addition, with regard to commercialization of these laser light sources, cost reduction by reducing device manufacturing 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.

As one conventional example for stabilizing the output of a solid state SHG laser light source, there is a laser diode pumped solid state laser disclosed in Japanese Patent Application Laid-Open No. Hei 8-181374 (first conventional example). This is APC for output stabilization.
Drives, but in order to further stabilize the output instability due to temperature instability in the optical components, to stabilize the temperature of the entire optical components using temperature control means It is. Specifically, as shown in FIGS. 7 and 8, a solid-state laser beam (second laser beam) emitted from a Fabry-Perot resonator 3 including an Nd: YAG crystal (laser crystal) 1 and a resonator mirror 2 is used. harmonic)
4 is detected by an APC photodetector 5, and based on an output signal of the photodetector 5, an APC circuit 6 controls the driving of a pumping semiconductor laser 7. Optical components such as a dichroic filter 8 disposed in an optical path where the laser beam (second harmonic) 4 reaches the photodetector 5 are maintained at a predetermined temperature by a temperature control means such as a Peltier element 9. Things. 10 is a heat sink. This allows
The laser output can be stabilized.

Another conventional example for stabilizing the output of a solid-state SHG laser light source is disclosed in Japanese Patent Application Laid-Open No. 9-6 / 1997.
There is a solid-state laser device disclosed in Japanese Patent No. 4471 (No. 2).
Conventional example). This is to stabilize the output by stabilizing the vertical mode and to suppress noise due to mode competition. Specifically, as shown in FIG. 9, an optical resonator 13 including a laser medium 11 and a nonlinear optical element 12 is provided.
And a semiconductor laser 14 that excites the laser medium 11, and converts a fundamental wave 15 generated in the laser medium 11 into a second harmonic by a nonlinear optical element 12 and emits output light 16. Wave 15 is optical resonator 1
3 is once more than half the loss of the fundamental wave 15 when the fundamental wave 15 makes one round trip through the optical resonator 13, and the wavelength conversion in the nonlinear optical element 12 is performed. The full width at half maximum of the efficiency is set to be equal to or more than の of the full width at half maximum of the natural emission intensity of the laser medium 11. As a result, the so-called green problem is eliminated, and the output is stabilized.

Another conventional example for stabilizing the output of a solid-state SHG laser light source is disclosed in Japanese Unexamined Patent Publication No.
There is a laser-diode-pumped solid-state laser device disclosed in Japanese Patent Application Publication No. 16 (third conventional example). This is to stabilize the output by placing a component holding a resonator or the like in a thermally and mechanically stable state for output stabilization. More specifically, as shown in FIG. 10, a laser diode pumped solid-state device that oscillates by irradiating a solid-state laser crystal 23 provided in a resonator 22 with pumping light output from a laser diode 21 to make it excited. In the laser device, each of the solid-state laser crystal 23 and the total reflection mirror 24 and the output mirror 25 constituting the resonator 22 are held by different holding members 26, 27, and 28, and the holding member 26 for the solid-state laser crystal 23 is thermally conducted. The holding members 27 and 28 for the total reflection mirror 24 and the output mirror 25 are formed of a material having a small coefficient of thermal expansion. As a result, the device becomes thermally stable, and the output is stabilized.

[0008]

However, in the case of the first conventional example, the heat generated in the excitation portion of the laser crystal 1 is large, and the temperature change due to this causes the output rise due to the temperature rise of the laser crystal 1 itself and the thermal lens effect. Causes stability. According to the examples shown in FIGS. 7 and 8, the heat dissipation of the laser crystal 1 is performed in a direction orthogonal to the excitation direction of the laser crystal 1, and the above-mentioned thermal problem is not improved. That is, the heat distribution of the laser crystal 1 itself and the output instability due to this heat distribution are not improved. In addition, the number of components is large, which hinders miniaturization and cost reduction.

The same applies to the case of the second conventional example, in which the heat generated in the excitation portion of the laser medium 11 is large, and a temperature change due to this causes an increase in the temperature of the laser medium 11 itself and output instability due to a thermal lens effect. According to the example shown in FIG. 9, heat is radiated from the laser medium 11 in a direction orthogonal to the excitation direction of the laser medium 11, and the above-described thermal problem is not improved. That is, the heat distribution of the laser medium 11 itself and the output instability due to the heat distribution are not improved. In addition, the temperature of the semiconductor laser 14 for excitation and the optical components are independently controlled, and the size and cost of the apparatus can be reduced by using a large lens for the condensing optical system of the semiconductor laser 14. There is a problem that cannot be achieved.

The same applies to the case of the third conventional example, in which the heat generated in the excited portion of the solid-state laser crystal 23 is large, and the temperature change due to this raises the temperature rise of the solid-state laser crystal 23 itself and the output instability due to the thermal lens effect. cause. According to the example shown in FIG. 10, the heat radiation of the solid-state laser crystal 23 is performed in a direction orthogonal to the excitation direction of the solid-state laser crystal 23, and the above-mentioned thermal problem is not improved. That is, the solid-state laser crystal 2
The heat distribution of 3 itself and the output instability due to this heat distribution are not improved. In addition, there is a problem that the use of two resonator mirrors or the use of a large lens for the condensing optical system of the laser diode 21 makes it impossible to increase the size and cost of the device.

As described above, although the conventional structure is intended to stabilize the output, there is nothing that can efficiently remove the heat generated by the laser crystal, and there is a limit to miniaturization of the device itself. That is, a solid-state SHG laser device having good output stability, small size, high efficiency, and excellent beam quality has not been completed yet, and its development is desired.

Therefore, the present invention provides a solid S which can stabilize the output without being adversely affected by the heat generated by the laser crystal.
An object of the present invention is to provide an HG laser device.

Another object of the present invention is to provide a solid-state SHG laser device that can be reduced in size and cost.

Another object of the present invention is to provide a solid-state SHG laser device capable of improving the transverse mode and increasing the efficiency.

A further object of the present invention is to provide a solid-state SHG laser device capable of improving efficiency and improving beam quality.

[0016]

According to the first aspect of the present invention,
A solid-state SHG laser including a laser crystal, a laser resonator for resonating laser light, a laser excitation light source for exciting the laser crystal, and a nonlinear optical crystal for generating a second harmonic in the laser resonator. In the apparatus, the laser crystal and the nonlinear optical crystal are in contact with each other,
An end face pumping structure is provided in which pumping light enters the laser crystal from the nonlinear optical crystal side.

Therefore, when the excitation light from the laser excitation light source is made incident on the laser crystal, the ions added to the laser crystal are excited, and fluorescence of a certain wavelength is emitted. Here, as the intensity of the excitation light is increased, the intensity of the fluorescent light is increased, the stimulated emission is started by the laser resonator, and when the intensity of the excitation light is further increased, laser oscillation is started to obtain a laser output. Can be At this time, the second harmonic is output by arranging the nonlinear optical crystal inside the resonator and setting the reflectivity of the resonator so as to confine the laser fundamental wave and output the second harmonic. It can be obtained efficiently. Here, the laser crystal and the nonlinear optical crystal are brought into contact with each other, and the end face excitation structure that excites from the nonlinear optical crystal side is used, so that heat generated by the laser crystal can be transferred to the nonlinear optical crystal side without using a special heat sink. Can be released to

According to a second aspect of the present invention, in the solid-state SHG laser device according to the first aspect, the laser resonator includes an end face of the laser crystal and an end face of the nonlinear optical crystal.

Therefore, in order to achieve the solid-state SHG laser device of the first aspect, the laser resonator is composed of the end face of the laser crystal and the end face of the nonlinear optical crystal, so that the size and cost can be reduced.

According to a third aspect of the present invention, in the solid-state SHG laser device according to the second aspect, the length of the nonlinear optical crystal in the optical axis direction is 1/5 or less of the effective crystal length.

The effective crystal length Leff of the nonlinear optical crystal is represented by Leff = 2Ws / (ρ / 2 ^1/2 ), where Ws is the beam radius in the crystal and ρ is the walk-off angle. By setting the length in the optical axis direction to 1/5 or less of the effective crystal length Leff, the allowable angle width of the phase matching can be increased and a stable output can be obtained.

According to a fourth aspect of the present invention, in the solid-state SHG laser device according to the first, second or third aspect, the laser excitation light source is a semiconductor laser.

Therefore, by using a semiconductor laser having a narrow half-width of the emission wavelength as a laser excitation light source and configuring it as a semiconductor laser excitation solid state SHG device, the stability of the laser excitation light source can be maintained. Stabilization can be achieved.

According to a fifth aspect of the present invention, there is provided the solid-state SHG laser device according to the fourth aspect, wherein a curvature shape having a condensing function is formed on an optically transparent substrate, and the excitation light from the semiconductor laser is formed. And a condensing optical element for converging light toward the laser resonator.

Therefore, by providing a condensing optical element for condensing the excitation light from the semiconductor laser toward the laser resonator, the transverse mode can be improved and the efficiency can be improved.

According to a sixth aspect of the present invention, in the solid-state SHG laser device according to the fifth aspect, the condensing optical element comprises:
It is fixed to and integrated with the nonlinear optical crystal.

Therefore, in order to achieve the solid-state SHG laser device according to the fifth aspect, the cost can be further reduced.

[0028] The invention according to claim 7 provides the invention according to claims 1 to 6.
In the solid-state SHG laser device according to any one of the above, an end face of the laser crystal forming the laser resonator is processed to have a radius of curvature.

Accordingly, the laser resonator has a semi-confocal resonator configuration, which is advantageous in achieving high efficiency and improving beam quality.

[0030] The invention according to claim 8 provides the invention according to claims 1 to 6.
In the solid-state SHG laser device according to any one of the above, an end face of the nonlinear optical crystal is processed into a radius of curvature shape.

Accordingly, the laser resonator has a semi-confocal resonator configuration, which is advantageous for improving the efficiency and improving the beam quality, and has a function of condensing the excitation light from the laser excitation light source. Can also.

The ninth aspect of the present invention relates to the first to sixth aspects.
In the solid-state SHG laser device according to any one of the above, an end face of the laser crystal forming the laser resonator and an end face of the nonlinear optical crystal are processed into a radius of curvature.

Accordingly, the laser resonator has a confocal resonator configuration, which is advantageous in improving the efficiency and improving the beam quality, and also has a function of condensing the pump light from the laser pump light source. it can.

[0034]

FIG. 1 shows a first embodiment of the present invention.
It will be described based on. FIG. 1 shows a solid SHG of the present embodiment.
FIG. 3 is a side view showing a laser 31. The solid-state SHG laser device 31 includes a semiconductor laser 32 as a laser excitation light source.
And a non-linear optical crystal 33, a laser crystal 34, and a laser output mirror 35 are sequentially arranged on the optical axis. Here, a laser resonator 36 is formed by the end face 33a of the nonlinear optical crystal 33 on the semiconductor laser 32 side and the laser output mirror 35, and the resonator length is, for example, 25 mm. Therefore, the laser crystal 34 and the nonlinear optical crystal 33 are disposed inside the laser resonator 36. As for the pumping, the end face pumping structure is used, and the output direction of the laser light 37 coincides with the pumping direction. The laser crystal 34 and the non-linear optical crystal 33 are fixed in contact with each other using an optically transparent adhesive.

Here, each component will be described in more detail. First, as the semiconductor laser 32 for exciting the laser crystal 34, a semiconductor laser having an emission center wavelength of 808 nm, a maximum output power of 1 W, and an emission area of 1 × 100 μm is used. The spread angle of light is 86.4 ° (= 1 / e ² ) in the V plane direction (direction perpendicular to the active layer) and 13.6 ° (= 1 / e) in the H plane direction (direction parallel to the active layer). ² ).

The laser crystal 34 is an a-cut YVO ₄ crystal in which Nd is added at 1.1 at%, and has a crystal size of 3 × 3 mm ² in cross section and 1 mm in crystal length. The both surfaces are coated with a multilayer film so as to enable laser oscillation, and the end face on the laser light incident side which is in contact with the nonlinear optical crystal 33 has a wavelength 8 which is excitation light.
The transmissivity is set higher than 08 nm (T> 99%), and the transmissivity is also set higher (T> 99%) at a wavelength of 1064 nm, which is a laser fundamental wave, and at a wavelength of 532 nm, which is a second harmonic. The laser output mirror side end face also has a wavelength of 1064 nm which is a fundamental laser beam and a wavelength of 532 which is a second harmonic.
The transmittance is also set high (T> 99%) for nm.

As the nonlinear optical crystal 33, a KTP crystal is used. Its crystal size is 4
× 4 mm ² , and the crystal length (thickness in the optical axis direction) is 1 mm
It has been. In this case, the effective crystal length of the KTP crystal is about 6.9 mm (the laser fundamental wave size in the resonator 36 is 11 mm).
0 μm), but the length is 以下 or less. The cut angle of the crystal is set to θ = 90 ° and φ = 23.5 ° so that type II phase matching can be performed with respect to a wavelength of 1064 nm which is a laser fundamental wave. Both end surfaces are coated with a multilayer film so as to enable laser oscillation. The surface in contact with the laser crystal 34 has a high transmittance (T> 99%) with respect to the wavelength of 808 nm, which is the excitation light, and has a wavelength of 1064 n, which is the laser fundamental wave.
The transmittance is also set high (T> 99%) for m and the wavelength 532 nm as the second harmonic. The semiconductor laser side end face also has a high transmittance (T> 99%) with respect to the wavelength of 808 nm which is the excitation light, and has the wavelength 1064 which is the laser fundamental wave.
The reflectance is set to be high (R> 99%) with respect to the wavelength of 532 nm and the second harmonic wavelength of 532 nm.

The laser output mirror 35 has a radius of curvature of 50 m.
A mirror with a diameter of 12.5 mm and a diameter of 12.5 mm is used. The laser output mirror 35 has a high reflectivity (R> 99%) for a laser fundamental wavelength of 1064 nm and a second harmonic wavelength of 532 nm so that the second harmonic can be efficiently extracted. It is formed to have a high transmittance (99%). With such a mirror configuration, a laser fundamental wave generated from the laser crystal 34 can be confined inside the laser resonator 36, and a highly efficient second harmonic output can be obtained as the laser light 37.

In such a configuration, the semiconductor laser 3
The excitation light output from 2 is incident on a laser crystal 34 made of Nd: YVO ₄ crystal through a nonlinear optical crystal 33 made of KTP crystal. Thereby, the center wavelength 1
064 nm fluorescence is generated, stimulated emission occurs in the laser resonator 36, and laser oscillation starts. Here, the laser resonator 36 is set so as to confine the laser fundamental wave (center wavelength of the excitation light) of 1064 nm as described above. Will exist. At this time, since the KTP crystal is arranged as the nonlinear optical crystal 33 in the laser resonator 36, the conversion to the second harmonic is performed with high efficiency by using the high-intensity laser fundamental wave in the laser resonator 36. Can do it. As a result, the output of the second harmonic can be output from the laser output mirror 35 as the laser light 37 with high efficiency.

At this time, this type of solid SHG laser device 1
One of the causes of the instability of the output is heat generation of the laser crystal 34. This is caused by the energy difference between the excitation wavelength and the oscillation wavelength.
In the case of such a short-plane excitation structure, a temperature gradient such as the center of the excitation portion or a Gaussian distribution is generated. Here, depending on the thermal conductivity of the laser crystal 34, the temperature gradient can be moderated to some extent. However, when the laser crystal 34 is placed in the air, there is a limit to heat dissipation, so that a refractive index distribution occurs, and the laser resonator 36 becomes unstable. Further, since the heat generation is greatest at the excitation side end face of the laser crystal 34, it can be said that removing the heat from this portion is most effective. In this regard, in the present embodiment, since the laser crystal 34 and the nonlinear optical crystal 33 are in contact with each other, the heat generated in the laser crystal 34 can be positively removed by the nonlinear optical crystal 33 and the laser crystal 34 Heat can be radiated from the portion generating the largest amount of heat, and it is thermally stable. Thus, the output can be stabilized without being adversely affected by heat.

The effective crystal length L of the nonlinear optical crystal 33 is
eff is represented by Leff = 2Ws / (ρ / 2 ^1/2 ), where Ws is the beam radius in the crystal and ρ is the walk-off angle. In the present embodiment, the nonlinear optical crystal 33 is used.
Has a length of 1 mm in the optical axis direction, and is 以下 or less of the effective crystal length Leff. Usually, in the second harmonic generation, a nonlinear optical crystal having a crystal length of about 5 mm is used for ease of use and miniaturization. However, in the conversion of the nonlinear optical crystal to the second harmonic,
The allowable width of the crystal angle is inversely proportional to the crystal length. That is, there is a 5-fold difference in the allowable angle width between the general example having a crystal length of 5 mm and the present embodiment having a crystal length of 1 mm. In the case of a general example having a crystal length of about 5 mm, alignment is required due to the narrow allowable width. However, according to the present embodiment having a crystal length of 1 mm, the second example can be efficiently performed only by contacting the laser crystal 34. Harmonics can be obtained. In addition, the laser fundamental wave converted into the second harmonic causes a reduction in the fundamental wave intensity due to the same effect as the internal loss, but the crystal length is reduced to 1/5 as in the present embodiment. Reduces internal loss by 1
/ 25 can be drastically reduced. Therefore, the degree of instability becomes 1/100 or less, and the output can be largely stabilized. In this embodiment, since the laser resonator 36 is a parallel plate resonator, the shorter the resonator length is, the more stable the laser output is. Therefore, it is important to set the nonlinear optical crystal 33 to 1 mm or less. is there.

In this embodiment, since the semiconductor laser 32 having a narrow half width of the emission wavelength is used as the laser excitation light source, the stability of the excitation light source can be maintained, and the output can be further stabilized. This is also advantageous for miniaturization.

A second embodiment of the present invention will be described with reference to FIG. FIG. 2 shows the solid-state SHG laser 4 of the present embodiment.
FIG. This solid SHG laser device 41
Is configured by sequentially disposing a semiconductor laser 42, a nonlinear optical crystal 43, and a laser crystal 44 as laser excitation light sources on an optical axis. Here, a laser resonator 45 is formed by the end face 43a of the nonlinear optical crystal 43 on the semiconductor laser 42 side and the end face 44a of the laser crystal 44 in the laser output direction, and the length of the resonator is, for example, about 2 mm.
It has been. Therefore, the laser crystal 44 and the nonlinear optical crystal 43 are disposed inside the laser resonator 45. As for the pumping, the end face pumping structure is used, and the output direction of the laser beam 46 and the pumping direction match. The laser crystal 44 and the nonlinear optical crystal 43 are fixed in a contact state using an optically transparent adhesive.

Here, each component will be described. First,
As the semiconductor laser 42, exactly the same as the semiconductor laser 32 is used. The laser crystal 44 is basically the same as the laser crystal 34, but the laser output side also functions as an output mirror with respect to the setting of the transmittance and the reflectance. For 1064 nm, the reflectance is high (R> 99).
%), And a multilayer film is formed such that the transmittance is high (99%) with respect to the wavelength 532 nm as the second harmonic.
As the nonlinear optical crystal 43, exactly the same as the nonlinear optical crystal 33 is used. With such a configuration of the laser resonator 45, a laser fundamental wave generated from the laser crystal 44 can be confined inside the laser resonator 45, and a highly efficient second harmonic output can be obtained as the laser beam 46. Can be

In such a configuration, the semiconductor laser 4
The excitation light output from 2 is incident on a laser crystal 44 made of Nd: YVO ₄ crystal through a nonlinear optical crystal 43 made of KTP crystal. As a result, the center wavelength 1
064 nm fluorescence is generated, stimulated emission occurs in the laser resonator 45, and laser oscillation starts. Here, the setting of the laser resonator 45 is set to the laser fundamental wave (the center wavelength of the excitation light) 1.
Since 064 nm can be confined, a high-intensity laser fundamental wave exists in the laser resonator 45. At this time, since the KTP crystal is arranged as the nonlinear optical crystal 43 in the laser resonator 45, the conversion to the second harmonic is performed with high efficiency by using the high-intensity laser fundamental wave in the laser resonator 45. Can do it. As a result, the output of the second harmonic as the laser beam 46 from the laser resonator 45 can be output with high efficiency.

At this time, also in this embodiment, the laser crystal 4
Since the non-linear optical crystal 43 is in contact with the non-linear optical crystal 43, the heat generated in the laser crystal 44 can be positively removed by the non-linear optical crystal 43, and the heat can be radiated from the portion of the laser crystal 44 which generates the most heat. Be thermally stable.
Thus, the output can be stabilized without being adversely affected by heat. Further, since the laser resonator 45 is constituted by the end face 43a of the nonlinear optical crystal 43 and the end face 44a of the laser crystal 44, the number of components can be reduced and the solid-state SHG laser device 41 can be miniaturized.
Cost reduction can be achieved.

Further, since the length of the nonlinear optical crystal 43 in the optical axis direction is 1 mm and is not more than 1/5 of the effective crystal length Leff, the laser crystal 44 and the laser crystal 44 have the same length as in the first embodiment. The second harmonic can be obtained efficiently only by contact, the internal loss can be drastically reduced to 1/25, the instability becomes 1/100 or less, and the output can be largely stabilized. . Further, in this embodiment, since the laser resonator 45 is a parallel plate resonator, the shorter the resonator length is, the more stable the laser output is.
It is important that the nonlinear optical crystal 43 be 1 mm or less.

Also, in this embodiment, since the semiconductor laser 42 having a narrow half width of the emission wavelength is used as the laser excitation light source, the stability of the excitation light source can be maintained, and the output can be further stabilized. This is also advantageous for miniaturization.

A third embodiment of the present invention will be described with reference to FIG. This embodiment is based on the second embodiment, and the same portions as those shown in FIG. 2 are denoted by the same reference numerals, and description thereof is omitted (the same applies to each of the following embodiments). And). FIG. 3 shows the solid SH of the present embodiment.
FIG. 2 is a side view showing a G laser 51. In the solid-state SHG laser 51 of the present embodiment, a condensing optical element 52 is added between the solid-state SHG laser 41 and the semiconductor laser 42 and the laser resonator 45. The condensing optical element 52 is a laser-side end face 43 of the nonlinear optical element 43.
a is fixed by an adhesive 53. here,
The condensing optical element 52 has a curvature shape 52b having a condensing function formed on an optically transparent substrate 52a for condensing the excitation laser light from the semiconductor laser 42. In the example, a biconvex lens shape is formed on a quartz substrate having a thickness of 550 μm. The convex lens shape at the curvature shape 52b on the excitation light incident side has a radius of curvature of 50 × 400.
It has a toric lens shape of μm, and the direction in which the radius of curvature of the semiconductor laser 42 is large corresponds to the direction in which the radius of curvature is small. The curvature shape 52b on the excitation light emission side is a circular lens shape having a radius of curvature of 400 μm. Further, an antireflection film made of a dielectric film is formed on both ends thereof, and the wavelength of the excitation light of the semiconductor laser 42 is 808 nm.
Anti-reflection measures are taken.

Also in the case of the present embodiment, operation is basically performed in the same manner as in the second embodiment, and similar effects are obtained. In addition, in the present embodiment, the condensing optical element 5 for condensing the excitation light from the semiconductor laser 42 having the curvature shape 52b formed on the optically transparent substrate 52a.
Since the number 2 is added, the efficiency of the excitation light to be incident on the laser crystal 44 can be improved, and the quality of the transverse mode can be improved according to the curvature shape 52b. At the same time, since the condensing optical element 52 is fixed to and integrated with the nonlinear optical crystal 43, the assembling process can be simplified and the cost can be reduced.

A fourth embodiment of the present invention will be described with reference to FIG. FIG. 4 shows a solid state SHG laser 6 according to the present embodiment.
FIG. In the solid-state SHG laser 61 of the present embodiment, a convex-shaped radius of curvature 62 having a curvature of 4 mm is formed on the laser output side end surface 44a of the laser crystal 44 forming the laser resonator 45 in the solid-state SHG laser 41 described above.
Are formed. Thus, the laser resonator 45 of the present embodiment has a semi-confocal resonator structure. Other points are the same as those of the solid-state SHG laser 41.

In the present embodiment, basically, the operation is the same as that of the second embodiment, and the same effect is obtained. In addition, in the present embodiment, since the laser resonator 45 has a semi-confocal resonator structure, the laser fundamental wave intensity in the nonlinear optical crystal 44 is larger than that of the parallel plate resonator structure. And the efficiency can be further improved. At the same time, the transverse mode quality of the laser can be improved.

A fifth embodiment of the present invention will be described with reference to FIG. FIG. 5 shows a solid-state SHG laser 7 of the present embodiment.
FIG. In the solid-state SHG laser 71 of the present embodiment, a convex-shaped radius of curvature 72 having a curvature of 4 mm is formed on the laser incident side end surface 43a of the nonlinear optical crystal 43 forming the laser resonator 45 in the solid-state SHG laser 41 described above. ing. Thus, the laser resonator 45 of the present embodiment has a semi-confocal resonator structure.
Other points are the same as those of the solid-state SHG laser 41.

In the case of the present embodiment, basically, the operation is the same as that of the second embodiment, and the same effect is obtained. In addition, in the present embodiment, since the laser resonator 45 has a semi-confocal resonator structure, the laser fundamental wave intensity in the nonlinear optical crystal 44 is larger than that of the parallel plate resonator structure. And the efficiency can be further improved. At the same time, the transverse mode quality of the laser can be improved. Further, the convex-shaped radius of curvature 72 is located on the side of the excitation light of the semiconductor laser 42 and has a function of condensing the excitation light. In this respect, the efficiency can be further improved.

A sixth embodiment of the present invention will be described with reference to FIG. FIG. 6 shows a solid state SHG laser 8 of the present embodiment.
FIG. In the solid-state SHG laser 81 of the present embodiment, the solid-state SHG laser 41 has a convex curvature radius shape 82 with a curvature of 2 mm on the laser output side end face 44a of the laser crystal 44 forming the laser resonator 45 in the solid-state SHG laser 41 described above.
Are formed, and a convex-shaped radius of curvature 83 having a curvature of 2 mm is formed on an end face 43 a on the laser incident side of the nonlinear optical crystal 43 forming the laser resonator 45. Thus, the laser resonator 45 of the present embodiment has a confocal resonator structure. Another point is that solid SH
It is similar to the G laser 41.

In the present embodiment, basically, the operation is the same as that of the second embodiment, and the same effect is obtained. In addition, in the present embodiment, since the laser resonator 45 has a confocal resonator structure, the laser fundamental wave intensity in the nonlinear optical crystal 44 is increased as compared with the parallel plate resonator structure. The efficiency can be further improved. At the same time, the transverse mode quality of the laser can be improved. Further, the semiconductor laser 42 has a convex radius of curvature 83 on the incident side of the excitation light and has a function of condensing the excitation light, so that the excitation light is condensed on the laser crystal 44 into a small spot. In this respect, the efficiency can be further improved.

In each of these embodiments, one type of semiconductor laser is shown as the semiconductor lasers 32 and 42 as the laser excitation light sources. However, the semiconductor lasers having an oscillation wavelength matching the absorption wavelength of the laser crystals 34 and 44 are shown. Any laser can be used, and a semiconductor laser having other characteristics can also be used. Regarding the laser crystals 34 and 44, the four-level system Nd:
Although described with reference to the example of a YVO ₄ crystal, the present invention is not particularly limited to this. For example, a four-level system Nd: YAG or Nd: L
SB or a three-level laser crystal (for example, Yb: YA
G) and the like are applicable. Further, the nonlinear optical crystals 33 and 43 are not limited to KTP, but may be, for example, BB.
Any crystal material such as O crystal, CLBO, LBO, KN, etc., which can be phase-matched to the laser fundamental wave, can be applied.

[0058]

According to the first aspect of the present invention, the laser crystal and the nonlinear optical crystal are in contact with each other, and the laser crystal has an end face pumping structure in which excitation light is incident on the laser crystal from the nonlinear optical crystal side. In order to efficiently obtain harmonics, heat generated by the laser crystal can be emitted to the nonlinear optical crystal without using a special heat sink or the like, and the output can be stabilized.

According to the second aspect of the present invention, in order to achieve the solid-state SHG laser device of the first aspect, the laser resonator is formed by the end face of the laser crystal and the end face of the nonlinear optical crystal, so that the size and size can be reduced. Cost reduction can be achieved.

According to the third aspect of the present invention, in the solid-state SHG laser device according to the second aspect, the length of the nonlinear optical crystal in the optical axis direction is set to 1/5 or less of the effective crystal length.
The angle tolerance of the phase matching can be increased, and a stable output can be obtained.

According to the invention described in claim 4, according to claim 1,
In the solid-state SHG laser device described in 2 or 3, the semiconductor laser-excited solid-state SHG device is configured by using a semiconductor laser having a narrow half-width of the emission wavelength as the laser excitation light source, so that the stability of the laser-excitation light source can be maintained. The output can be further stabilized by reducing the size.

According to the fifth aspect of the present invention, the solid-state SHG laser device according to the fourth aspect is provided with the condensing optical element for condensing the excitation light from the semiconductor laser toward the laser resonator. In addition, the lateral mode can be improved and the efficiency can be increased.

According to the sixth aspect of the present invention, in the solid state SHG laser device according to the fifth aspect, the condensing optical element is fixed to and integrated with the nonlinear optical crystal. In achieving the SHG laser device, further cost reduction can be achieved.

According to a seventh aspect of the present invention, in the solid-state SHG laser device according to any one of the first to sixth aspects, the end face of the laser crystal forming the laser resonator is processed into a radius of curvature. Therefore, the laser resonator has a semi-confocal resonator configuration, which is advantageous in achieving high efficiency and improving beam quality.

According to the eighth aspect of the present invention, in the solid-state SHG laser device according to any one of the first to sixth aspects, the end face of the nonlinear optical crystal is processed into a radius of curvature, so that the laser resonator is formed. Becomes a semi-confocal resonator configuration,
In addition to being advantageous in achieving high efficiency and improving the beam quality, it can also have a function of condensing the excitation light from the excitation light source.

According to the ninth aspect of the present invention, in the solid-state SHG laser device according to any one of the first to sixth aspects, the end face of the laser crystal forming the laser resonator and the end face of the nonlinear optical crystal have a radius of curvature. Because it is processed into a shape, the laser resonator has a confocal resonator configuration, which is advantageous for achieving high efficiency and improving beam quality, and has a function of condensing excitation light from the excitation light source. You can also.

[Brief description of the drawings]

FIG. 1 is a side view showing a solid-state SHG laser according to a first embodiment of the present invention.

FIG. 2 is a side view showing a solid-state SHG laser according to a second embodiment of the present invention.

FIG. 3 is a side view showing a solid-state SHG laser according to a third embodiment of the present invention.

FIG. 4 is a side view showing a solid-state SHG laser according to a fourth embodiment of the present invention.

FIG. 5 is a side view showing a solid-state SHG laser according to a fifth embodiment of the present invention.

FIG. 6 is a side view showing a solid-state SHG laser according to a sixth embodiment of the present invention.

FIG. 7 is a plan view showing a first conventional example.

FIG. 8 is a side view thereof.

FIG. 9 is a side view showing a second conventional example.

FIG. 10 is a plan view showing a third conventional example.

[Explanation of symbols]

 Reference Signs List 32 semiconductor laser, laser excitation light source 33 nonlinear optical crystal 34 laser crystal 36 laser resonator 42 semiconductor laser, laser excitation light source 43 nonlinear optical crystal 43a end face 44 laser crystal 44a end face 45 laser resonator 52 light-collecting optical element 52a substrate 52b curvature Shape 62,72,82,83 Radius of curvature

Claims (9)

[Claims] 1. A laser crystal, a laser resonator for resonating laser light, a laser excitation light source for exciting the laser crystal, and a non-linear optical crystal for generating a second harmonic in the laser resonator. A solid-state SHG laser device comprising: a solid-state SHG having an end-face excitation structure in which the laser crystal and the nonlinear optical crystal are in contact with each other and excitation light is incident on the laser crystal from the nonlinear optical crystal side. Laser device. 2. The solid-state SHG laser device according to claim 1, wherein said laser resonator comprises an end face of said laser crystal and an end face of said nonlinear optical crystal. 3. The solid-state SHG laser device according to claim 2, wherein the length of the nonlinear optical crystal in the optical axis direction is 1/5 or less of the effective crystal length. 4. The solid state S according to claim 1, wherein said laser excitation light source is a semiconductor laser.
HG laser device. 5. A condensing optical element having a curved shape having a condensing function formed on an optically transparent substrate and condensing excitation light from the semiconductor laser toward the laser resonator. The solid-state SHG laser device according to claim 4, comprising: 6. The solid-state SHG laser device according to claim 5, wherein said condensing optical element is fixed to and integrated with said nonlinear optical crystal. 7. The solid SHG according to claim 1, wherein an end face of the laser crystal forming the laser resonator is processed to have a radius of curvature.
Laser device. 8. An end face of said nonlinear optical crystal is processed into a radius of curvature shape.
The solid-state SHG laser device according to any one of the above. 9. An end face of said laser crystal forming said laser resonator and an end face of said nonlinear optical crystal are processed into a radius of curvature.
The solid-state SHG laser device according to any one of the above.