JP2000124533A - Solid laser equipment - Google Patents

Abstract

(57) Abstract: The present invention provides a small-sized solid-state laser device with improved heat radiation and stable output. A solid-state laser device includes a semiconductor laser.
The laser light emitted from the laser light is made incident on the laser crystal 5 through the optical transparent substrate 4 by the condensing optical system 3, and the laser crystal 5 generates fluorescence by the incidence of the laser light, and stimulated emission occurs in the laser resonator 7. This causes laser oscillation. The laser resonator 7 is formed between the incident facet of the laser crystal 5 and the facet of the nonlinear optical crystal 6 on the laser emission side. The laser resonator 7 confines the laser fundamental wave inside and generates a second harmonic with high efficiency. Let it. The laser crystal 5 has an optically transparent substrate 4 on the end face of the laser beam incident side.
However, since the nonlinear optical crystal 6 is in contact with and arranged on the end face on the side of the laser resonator 7, heat generated in the laser crystal 5 is efficiently radiated from a portion having the largest heat generation in a direction parallel to the excitation direction, Output can be stabilized.

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, and more particularly, to a small-sized solid-state laser device having improved heat radiation and more stable output.

[0002]

2. Description of the Related Art In recent years, research and development and commercialization of semiconductor laser-excited solid-state lasers have been actively pursued along with the cost reduction of high-power semiconductor lasers.

The semiconductor laser pumped solid-state laser has a very high efficiency because the spectrum width of the pump light source is narrower than that of the conventional lamp pumped laser. A laser suitable for high efficiency. Semiconductor laser-excited solid-state lasers are capable of high-power continuous-wave oscillation at room temperature and high-quality laser oscillation, and are also extremely excellent in energy storage and frequency stability. .

For this reason, expectations have been gathered as a small, highly efficient and high-quality laser light source, and wavelength conversion technology using a solid-state laser and a non-linear optical crystal has been actively researched, developed and commercialized. 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 wavelength, it can be used as a visible light source such as blue-green in the future. It is expected as an excitation light source for an ultraviolet light source by generation of four harmonics, and research and product development are being actively conducted.

The applications of these laser light sources are diverse, such as processing, measurement, and communication. However, in light sources such as light sources for optical printers and optical pickups, the stability and efficiency of the light source are improved, and the lateral mode quality is improved. There is a demand for higher quality. As for the commercialization of these laser light sources, there is also a demand for cost reduction by reducing device manufacturing costs and component costs. That is, a laser light source with high efficiency, high quality, and low price is expected as a commercial product, and various inventions and researches have been conventionally made.

For example, Japanese Patent Application Laid-Open No. 8-181374 proposes a laser diode pumped solid-state laser whose output is stabilized. This laser diode pumped solid-state laser, a photodetector that detects the light intensity of at least a part of the solid-state laser beam emitted from the resonator,
An APC circuit that controls the driving of the laser diode based on the output signal of the photodetector; and an optical component disposed on an optical path from the solid-state laser beam emitted from the resonator to the photodetector, at a predetermined temperature. And temperature control means for maintaining the temperature. That is, to stabilize the output, APC (Automatic Power Control)
While driving, the temperature of the entire optical component is stabilized using a temperature control mechanism, and the output instability due to the temperature instability in the optical component is achieved, thereby stabilizing the laser output. Then, as shown in the embodiment, heat radiation of the laser crystal is performed in a direction orthogonal to the excitation direction of the laser crystal.

For example, Japanese Patent Application Laid-Open No. 9-64471 discloses an optical resonator including a laser medium and a nonlinear optical element, and a pumping light source for exciting the laser medium. In a solid-state laser device that converts a fundamental wave into a second harmonic by using a nonlinear optical element and outputs the fundamental wave, the efficiency with which the fundamental wave is converted into a second harmonic when passing through the nonlinear optical element once is determined by the optical resonance. More than half of the loss of one round trip of the vessel,
In addition, a solid-state laser has been proposed, wherein the full width at half maximum of the wavelength conversion efficiency in the nonlinear optical element is at least half the full width at half maximum of the natural emission intensity corresponding to the fundamental wave of the laser medium. I have. In this solid-state laser, the efficiency with which a laser fundamental wave is converted into a second harmonic when passing once through a nonlinear optical element is equal to one loss of the resonator loss.
/ 2, and the full width at half maximum of the wavelength conversion efficiency of the nonlinear optical element is equal to or more than 1/2 of the full width at half maximum of the natural emission intensity corresponding to the fundamental wave of the laser medium. The mode competition noise is suppressed by unification, so-called green problem is eliminated, and the output is stabilized. Then, as shown in the embodiment, heat radiation of the laser crystal is performed in a direction orthogonal to the excitation direction of the laser crystal.

Further, Japanese Patent Application Laid-Open No. Hei 9-116216 discloses a laser diode which oscillates by irradiating a solid laser crystal provided in a resonator with excitation light output from a laser diode to make it excited. In the pumped solid-state laser device, each of the solid-state laser crystal and the total reflection mirror and the output mirror constituting the resonator is held by different holding members, and the holding member of the solid-state laser crystal is formed of a material having high thermal conductivity. A laser-diode-pumped solid-state laser device has been proposed in which the holding members of the reflection mirror and the output mirror are formed of a material having a small thermal expansion coefficient. Specifically, in order to stabilize the output, each of the total reflection mirror and the output mirror constituting the laser crystal or laser resonator is held by a different holding member, and the solid laser crystal holding member is made of a material having high thermal conductivity. The holding members for the total reflection mirror and the output mirror are made of a material having a small coefficient of thermal expansion. Further, as shown in the embodiment, heat radiation of the laser crystal is performed in a direction orthogonal to the excitation direction of the laser crystal.

[0009]

However, in the laser diode-pumped solid-state laser described in Japanese Patent Application Laid-Open No. 8-181374, the temperature of the entire optical component is stabilized using a temperature control mechanism. In particular,
As described in the embodiment, since the heat radiation of the laser crystal is performed in the direction orthogonal to the excitation direction of the laser crystal, the heat generated in the excitation part of the laser crystal is large. There is a problem that the heat distribution and the output instability due to the heat distribution cannot be eliminated, and the laser output becomes unstable. In addition, the number of parts is large,
This was a problem in reducing the size and cost.

In the solid-state laser disclosed in Japanese Patent Application Laid-Open No. 9-64471, heat is radiated from the laser crystal in a direction perpendicular to the excitation direction of the laser crystal. There is a problem that the output becomes unstable due to the lens effect. In addition, the temperature of the semiconductor laser for excitation and the optical components are independently controlled, and a large lens is used for the condensing optical system of the semiconductor laser. .

Further, even in the laser diode-pumped solid-state laser device described in Japanese Patent Application Laid-Open No. Hei 9-116216, since the heat is radiated from the laser crystal in a direction perpendicular to the laser crystal excitation direction, the temperature of the laser crystal itself is reduced. There has been a problem that the output becomes unstable due to the rise or the thermal lens effect. Also, using two resonator mirrors,
Since a large lens is used for the condensing optical system of the semiconductor laser, there is a problem that the apparatus becomes large and the cost is high.

Therefore, according to the first aspect of the present invention, an optically transparent excitation light emitted from an excitation light source is provided on an incident side end face of a laser crystal where the excitation light is condensed via a condensing optical system. By contacting the transparent substrate and bringing the non-linear optical crystal into contact with the end face of the laser crystal on the emission side of the laser light, a laser resonator is constituted by the laser crystal and the non-linear optical crystal and resonated by the laser resonator. To stabilize the output by emitting laser light and efficiently radiating heat generated at the laser crystal excitation light incident part from the transparent substrate and the nonlinear optical crystal that are in contact with both ends of the laser crystal in the excitation direction. It is an object of the present invention to provide a solid-state laser device capable of performing the above.

According to a second aspect of the present invention, a laser resonator is formed by utilizing an end face of a laser crystal on an incident side of excitation light and an end face of a nonlinear optical crystal on an emission side of a laser beam. While shortening the length of
It is an object of the present invention to provide a small and inexpensive solid-state laser device that can reduce the number of components and stabilize the output.

According to a third aspect of the present invention, by setting the length of the nonlinear optical crystal in the optical axis direction to be 1/5 or less of the effective crystal length, the allowable angle width of the nonlinear optical crystal is increased by a factor of five. In addition, the internal loss of the laser resonator is reduced to 1/25 or less, and the external influence is suppressed to 1/100 or less, that is, 2 digits or less, so that the output is further stabilized and the size is further reduced. It is intended to provide a solid-state and inexpensive solid-state laser device.

According to a fourth aspect of the present invention, the length of the laser crystal in the optical axis direction is set to be equal to or less than half the absorption length of the excitation light, so that the excitation light passes through the laser crystal a plurality of times. Improves the absorption efficiency of the pumping light of the crystal, and evens out the heat generated by the laser crystal, thereby improving the heat radiation efficiency, reducing the generation of heat distribution, stabilizing the output, and reducing the size. It is intended to provide a solid-state and inexpensive solid-state laser device.

According to a fifth aspect of the present invention, as the excitation light source,
An object of the present invention is to provide a solid-state laser device that is smaller and more efficient by using a semiconductor laser light source to reduce the size of the excitation light source and efficiently perform excitation.

According to a sixth aspect of the present invention, an optical element having a curvature shape formed on a predetermined optically transparent substrate is used as a condensing optical system, so that the condensing optical system can be downsized. An object of the present invention is to provide a more compact solid-state laser device that excites a laser crystal with a small spot diameter close to a circle, improves transverse mode quality, and is more compact.

An object of the present invention is to provide an even more inexpensive solid-state laser device in which an optical element as a light-collecting optical system is fixed to a transparent substrate to facilitate alignment and further reduce the cost. .

According to the present invention, the transparent substrate and the nonlinear optical crystal are housed in a predetermined case, and the outer peripheral end of the transparent substrate and the nonlinear optical crystal are brought into contact with the inside of the case, so that the excitation light incident portion of the laser crystal can enter the case. The purpose of the present invention is to provide a solid-state laser device capable of efficiently radiating heat generated from a transparent substrate and a nonlinear optical crystal in contact with both end surfaces in the excitation direction of a laser crystal to a case and further stabilizing the output. I have.

According to a ninth aspect of the present invention, the transparent substrate is formed of a sapphire substrate so that the transmittance of the excitation light is 9%.
9.9% or more, the thermal conductivity of the laser crystal is 4 to 1
It is an object of the present invention to provide a solid-state laser device capable of increasing the heat radiation property to about 0 times, further improving the heat radiation property, lowering the birefringence property, and further stabilizing the output with higher efficiency. .

[0021]

According to a first aspect of the present invention, there is provided a solid-state laser device, comprising: a pump light emitted from a predetermined excitation light source; Condensing on the crystal to excite the laser crystal,
In a solid-state laser device that resonates with the laser resonator and emits laser light, an optically transparent predetermined transparent substrate is brought into contact with an end surface of the laser crystal on the incident side of the excitation light, and The above object is achieved by bringing a predetermined nonlinear optical crystal into contact with the end face on the laser light emission side.

That is, a solid-state laser device includes an excitation light source for emitting excitation light to a laser crystal, a laser resonator having a built-in laser crystal, and condensing optics for condensing excitation light emitted from the excitation light source to the laser crystal. And a system,
The transparent substrate is in contact with the excitation light incident side end face of the laser crystal, and the nonlinear optical crystal is in contact with the laser light emission side end face of the laser crystal.

Therefore, in a solid-state laser device, when excitation light emitted from an excitation light source is made incident on a laser crystal provided in a laser resonator by a condensing optical system, ions added to the laser crystal are excited. It is excited by light and emits fluorescence of a certain wavelength. At this time, if the intensity of the excitation light is increased, the intensity of the fluorescence is increased in accordance with the intensity of the excitation light, stimulated emission is started by the laser resonator, and if the intensity of the excitation light is further increased, the intensity of the laser is increased. Oscillation starts. At this time, by setting the reflectivity of the laser output mirror high for the laser fundamental wave and low for the second harmonic, the second harmonic converted by the nonlinear optical element arranged in the laser resonator is obtained. Can be taken out efficiently.

In the solid-state laser device, since the transparent substrate and the non-linear optical crystal are in contact with both end faces in the excitation direction of the laser crystal, the heat generation of the laser crystal by the excitation light is caused by the laser crystal in a direction parallel to the excitation direction. Heat can be efficiently radiated through the transparent substrate and the nonlinear optical crystal that are in contact with both end surfaces.

As described above, according to the above configuration, the optically transparent excitation light emitted from the excitation light source is formed on the incident side end face of the excitation light of the laser crystal which is condensed through the condensing optical system. Since the transparent substrate is brought into contact with the non-linear optical crystal at the end face of the laser crystal on the laser light emission side, a laser resonator is composed of the laser crystal and the non-linear optical crystal, and the laser resonator is caused to resonate. The laser beam can be emitted from the laser crystal, and the heat generated at the laser crystal excitation light incident part is efficiently radiated from the transparent substrate and the nonlinear optical crystal that are in contact with both ends in the laser crystal excitation direction, and the output is stabilized. Can be changed.

In this case, for example, as set forth in claim 2, the laser resonator is configured such that an end face of the laser crystal on the incident side of the excitation light and an end face of the nonlinear optical crystal on the emission side of the laser light. It may be formed by utilizing.

According to the above configuration, the laser resonator is formed using the end face of the laser crystal on the incident side of the excitation light and the end face of the nonlinear optical crystal on the emission side of the laser light. The length can be shortened, the number of components can be reduced, the output can be stabilized, and the solid-state laser device can be made small and inexpensive.

Further, for example, as set forth in claim 3, the nonlinear optical crystal may have a length in the optical axis direction which is equal to or less than one fifth of an effective crystal length.

Here, the length of the nonlinear optical crystal in the direction of the optical axis is set to 1/5 or less of the effective crystal length. The effective crystal length Leff is expressed by the following equation.

Leff = 2Ws / (ρ / 2 ^1/2 ) where Ws is the beam radius in the nonlinear optical crystal, and ρ is
The walk-off angle.

When the length of the nonlinear optical crystal in the direction of the optical axis is made not more than one fifth of the effective crystal length, the allowable angle width of the nonlinear optical crystal can be increased by a factor of five, and the loss inside the laser resonator can be reduced by 1 /. The size can be reduced to 25 or less, and the external influence can be suppressed to 1/100 or less, that is, 2 digits or less.

As described above, according to the above configuration, the length of the nonlinear optical crystal in the direction of the optical axis is set to 1/5 or less of the effective crystal length. The resonator length of the resonator can be shortened, the allowable angle width of the nonlinear optical crystal can be increased five times, and the loss inside the laser resonator can be reduced by one.
/ 25 or less, the external influence can be suppressed to 1/100 or less, that is, two digits or less, the output can be further stabilized, and the solid-state laser device can be further miniaturized. And inexpensive.

Further, for example, the length of the laser crystal in the optical axis direction may be equal to or less than half of the absorption length for the excitation light.

According to the above configuration, the length of the laser crystal in the optical axis direction is set to be equal to or less than half of the absorption length of the excitation light, so that the excitation light passes through the laser crystal a plurality of times. The efficiency of light absorption can be improved, and the heat generated by the laser crystal can be made uniform, the heat radiation efficiency can be improved, and the occurrence of heat distribution can be reduced. It can be more stable, smaller and cheaper.

Also, for example, the excitation light source may be a semiconductor laser light source.

According to the above configuration, since the semiconductor laser light source is used as the excitation light source, the excitation light source can be reduced in size, the excitation can be performed efficiently, and the solid-state laser device can be made more compact. And higher efficiency.

Further, for example, the converging optical system may be an optical element having a curvature shape formed on a predetermined optically transparent substrate.

According to the above configuration, since the optical element having a curved shape formed on a predetermined optically transparent substrate is used as the light-collecting optical system, the light-collecting optical system can be downsized. At the same time, the laser crystal is excited with a small and nearly circular spot diameter, so that the transverse mode quality can be improved, and the solid-state laser device can be made smaller and more efficient.

Further, for example, the optical element may be fixed to the transparent substrate.

According to the above configuration, since the optical element as the condensing optical system is fixed to the transparent substrate, alignment can be facilitated, and the solid-state laser device can be made more inexpensive. it can.

Further, for example, as described in claim 8, the transparent substrate and the nonlinear optical crystal are housed in a predetermined case, and the outer peripheral end thereof is in contact with the inside of the case. Is also good.

According to the above configuration, the transparent substrate and the nonlinear optical crystal are housed in the predetermined case, and the outer peripheral end thereof is in contact with the inside of the case. Heat can be efficiently radiated to the case from the transparent substrate and the nonlinear optical crystal that are in contact with both end faces in the excitation direction of the laser crystal, and the output can be further stabilized.

Also, for example, the transparent substrate may be a sapphire substrate.

According to the above configuration, since the transparent substrate is formed of the sapphire substrate, the transmittance of the excitation light is 99.9.
% Or more, the thermal conductivity can be increased to about 4 to 10 times that of the laser crystal, the heat dissipation can be further improved, and the birefringence is reduced, so that the solid-state laser device can be further improved. The output can be further stabilized with efficiency.

[0045]

Preferred embodiments of the present invention will be described below in detail with reference to the accompanying drawings. It should be noted that the embodiments described below are preferred embodiments of the present invention, and therefore, various technically preferable limitations are added. However, the scope of the present invention is not limited to the following description. The embodiments are not limited to these embodiments unless otherwise specified.

FIG. 1 shows a first embodiment of the solid-state laser device according to the present invention.
1 is a front view of a solid-state laser device 1 to which the embodiment is applied.

In FIG. 1, a solid-state laser device 1 includes a semiconductor laser 2 as an excitation light source, a condensing optical system 3, an optically transparent substrate 4, a laser crystal 5, and a nonlinear optical crystal 6. The condensing optical system 3, the optically transparent substrate 4, the laser crystal 5, and the nonlinear optical crystal 6 are arranged in this order in the optical axis direction of the laser as the excitation light emitted from the semiconductor laser 2.

The semiconductor laser 2 has a center wavelength of 808n.
m, the output is 1 W, and the emission diameter is 1 × 100 μm.

The condenser optical system 3 is constituted by combining an aspheric lens having a focal length of 3 mm. The aspherical lens constituting the condensing optical system 3 is provided with an AR coating having a transmittance of 99% with respect to a wavelength of 808 nm of the laser light, and condenses the laser light emitted from the semiconductor laser 2. Then, the light is made to enter the laser crystal 5 through the optically transparent substrate 4.

The optically transparent substrate 4 is made of sapphire and has an aperture size of 5 mm × 5 mm and a substrate thickness of 0.5 mm. The optical transparent substrate 4 is coated with a dielectric multilayer film on both end faces in the direction of incidence and emission of laser light, and both end faces have a transmittance of 99.9% with respect to a laser wavelength of 808 nm.

The laser crystal 5 has its semiconductor laser 2
A non-linear optical crystal 6 is adhered to the opposite end face, that is, the end face of the laser light emission side, by an optically transparent adhesive while being in contact with the optical transparent substrate 4. In the state of being in contact, it is adhesively fixed with an optically transparent adhesive. The laser crystal 5 and the non-linear optical crystal 6 form a laser resonator 7 between the laser emission side end faces of the laser crystal 5 and the non-linear optical crystal 6, and the laser resonator 7 is non-linear with the laser crystal 5. In this state, the optical crystal 6 is incorporated. Laser resonator 7
Has an end-pumped configuration, in which the laser light output direction and the excitation direction are the same.

The laser crystal 5 is made of Nd: LSB (LaSc ₃ (BO ₃ ) ₄ ) containing 10% of neodymium (Nd).
A crystal having an aperture size of 4
mm × 4 mm, and the crystal length is 1 mm. The laser crystal 5 has a dielectric multi-layer coating on both end faces, and the end face on the excitation side by the semiconductor laser 2 is:
98% transmittance for the excitation wavelength of 808 nm,
The reflectivity with respect to 1062 nm which is the laser fundamental wave and 531 nm which is the second harmonic is 99.9%, and the end face in contact with the nonlinear optical crystal 6 is 1062 nm which is the laser fundamental wave. 531n which is 2 harmonics
With respect to m, the transmittance is 99.9%.

As the nonlinear optical crystal 6, a KTP crystal is used, and the crystal size is 3 mm × aperture size.
The crystal length is 3 mm and the crystal length is 1 mm. The nonlinear optical crystal 6 has an effective crystal length of 69 m because the fundamental wave spot size in the laser resonator 7 is about 110 μm.
m, and the cut angle of the crystal is set to θ = 90 degrees and φ = 23.5 degrees so that Type II phase matching can be performed with respect to the laser fundamental wave of 1062 nm. The non-linear optical crystal 6 is coated with a dielectric multilayer film on both end faces in the direction of incidence and emission of laser light, and the end face on the side of the laser crystal 5 has a laser fundamental wave of 1062n.
The transmittance is 99.9% for m and 531 nm, which is the second harmonic, and the end face on the laser light output side has a reflectance of 992 nm for the laser fundamental wave, 1062 nm. 2.9% to 631 nm which is the second harmonic
Is 98%.

Next, the operation of the present embodiment will be described. The solid-state laser device 1 emits laser light from a semiconductor laser 2 in the direction of a condensing optical system 3 as shown by a broken line in FIG. Laser crystal 5 through transparent substrate 4
Incident on

When the laser beam is incident on the laser crystal 5, the laser crystal 5 generates fluorescence having a center wavelength of 1062.5 nm, stimulated emission occurs in the laser resonator 7, and laser oscillation occurs.

Since the laser resonator 7 is set so as to confine the laser fundamental wave (1062.5 nm) in the laser resonator 7 as described above, the laser resonator 7 has a high intensity. Laser fundamental wave exists. The laser resonator 7 is formed between the laser crystal 5 and the end face of the nonlinear optical crystal 6 on the laser light emission side, and has the laser crystal 5 and the nonlinear optical crystal 6 incorporated therein. Therefore,
A high-efficiency second harmonic can be generated by using a high-intensity laser fundamental wave existing in the laser resonator 7, and the second harmonic can be obtained efficiently.

The laser resonator 7 has an end-pumped structure, and the heat generated by the laser crystal 5 is generated by the energy difference between the excitation wavelength and the oscillation wavelength. A gradient occurs. The temperature gradient in the laser crystal 5 becomes gentle to some extent due to the heat conduction of the laser crystal 5, but when the laser crystal 5 is placed in the air, its heat radiation is limited, and the refractive index distribution due to heat is generated. The output of the resonator 7 becomes unstable.

However, in the solid-state laser device 1, the optical transparent substrate 4 is disposed in contact with the excitation side of the laser crystal 5, and the laser resonator 5 side of the laser crystal 5 is
That is, the nonlinear optical crystal 6 is disposed in contact with the laser light emission side. Therefore, the heat generated in the laser crystal 5 is efficiently radiated in the direction parallel to the excitation direction from the portion that generates the most heat, so that the instability of the laser resonator 7 due to the heat can be reduced and the output can be stabilized. Can be.

Further, when generating the second harmonic, the nonlinear optical crystal 6 is usually formed to have a crystal length of about 5 mm for ease of use and miniaturization. Reference numeral 1 indicates that the crystal length of the nonlinear optical crystal 6 is 1 mm, which is 1/5 or less of the effective crystal length. And
In the conversion of the nonlinear optical crystal 6 to the second harmonic, the allowable width of the crystal angle is inversely proportional to the crystal length. That is, the nonlinear optical crystal 6 has a crystal length of 5 mm and a crystal length of 1 mm.
In this case, the angle allowable width has a five-fold difference. Normally, a nonlinear optical crystal 6 using a KTP crystal of about 5 mm
It is necessary to perform alignment because the allowable width of the crystal angle is narrow, but when the crystal length is 1 mm, the second harmonic can be efficiently obtained only by contacting with the laser crystal 5, The workability of the assembling work can be improved, and the cost can be reduced.

The fundamental wave converted to the second harmonic is
This has the same effect as the internal loss, and causes a decrease in the fundamental wave intensity. However, in the solid-state laser device 1, since the crystal length of the nonlinear optical crystal 6 is set to 1 mm which is 1/5 or less of the effective crystal length, the internal loss can be reduced to 1/25, and the instability is reduced to 1/100, that is, , The output can be reduced to two digits or less, and the output can be stabilized.

Further, the laser resonator 7 composed of the laser crystal 5 and the nonlinear optical crystal 6 is a parallel plate resonator. The shorter the resonator length is, the more stable the laser output is. Is formed to 1 mm or less, so that the laser output can be stabilized.

FIG. 2 shows a second embodiment of the solid-state laser device according to the present invention.
1 is a front view of a solid-state laser device 10 to which the embodiment of the present invention is applied.

In FIG. 2, the solid-state laser device 10
Semiconductor laser 11 as excitation light source, focusing optical element 1
2, comprising an optically transparent substrate 13, a laser crystal 14, and a nonlinear optical crystal 15, a semiconductor laser 11, a condensing optical element 12, an optically transparent substrate 13, and a laser crystal 14.
The laser light serving as the excitation light emitted from the semiconductor laser 11 is arranged in the order of the nonlinear optical crystal 15 in the optical axis direction of the laser.

The semiconductor laser 11 has a center wavelength of 808.
nm, the output was 1 W, and the emission diameter was 1 × 100 μm.

The condensing optical element 12 is formed of a micro optical element having a convex lens shape (curvature shape) formed on both sides of a quartz substrate having a thickness of 550 μm. That is, the condensing optical element 12 has a curvature radius of 50 μm
A toric lens of × 400 μm is formed, and the direction in which the divergence angle of the laser beam is large corresponds to the direction in which the radius of curvature is small.
A 0 μm circular lens is formed. The light-collecting optical element 12 is subjected to anti-reflection treatment by a dielectric multilayer film on both surfaces thereof, so that the transmittance is 99% with respect to the wavelength of 808 nm of the laser light. The condensing optical element 12 is fixed to an optically transparent substrate 13,
Laser light emitted from the semiconductor laser 11 is condensed and made incident on the laser crystal 14 through the optically transparent substrate 13.

The optically transparent substrate 13 is made of sapphire and has an aperture size of 5 mm × 5 mm and a thickness of 0.5 mm. The optically transparent substrate 13 is coated with a dielectric multilayer film on both end faces in the direction of incidence and emission of laser light, and both end faces have a transmittance of 99.9% with respect to a laser wavelength of 808 nm.

The laser crystal 14 is provided with an optically transparent substrate 4 which is adhered with an optically transparent adhesive while being in contact with the end face on the semiconductor laser 11 side. A non-linear optical crystal 15 is disposed in a state of being contacted with an optically transparent adhesive. The laser crystal 14 and the nonlinear optical crystal 15 form a laser resonator 16 between the laser emission side end faces of the laser crystal 14 and the nonlinear optical crystal 15, and the laser resonator 16 is nonlinear with the laser crystal 14. In this state, the optical crystal 15 is incorporated.

This solid-state laser device 1 is of an end-pumped type, and the laser beam output direction and the pumping direction are the same.

The laser crystal 14 is made of neodymium (Nd)
: 10% Nd: LSB (LaSc ₃ (B
O ₃ ) ₄ ) crystal having an aperture size of 4 mm × 4 mm and a crystal length of 1 mm, which is an absorption length.
0.5 mm, which is half or less of the above. Laser crystal 1
Numeral 4 is coated with a dielectric multilayer film on both sides, and the end face on the excitation side of the semiconductor laser 11 has a transmittance of 98% for an excitation wavelength of 808 nm and a laser fundamental wave of 1062 nm, which is the second. 531 which is a harmonic
The reflectance with respect to nm is 99.9%. The end face of the laser crystal 14 that is in contact with the nonlinear optical crystal 15 has a reflectivity of 99.9% for an excitation wavelength of 808 nm, a laser fundamental wave of 1062 nm and a second harmonic of 531 nm. Is coated with a dielectric multilayer film so as to have a transmittance of 99.9%.

The nonlinear optical crystal 15 uses a KTP crystal, and the crystal size is 3 mm.
× 3 mm and a crystal length of 1 mm. Since the nonlinear optical crystal 15 has a fundamental wave spot size of about 110 μm in the laser resonator 16, its effective crystal length is 69 mm, and the cut angle of the crystal is Type II phase matching with respect to the laser fundamental wave of 1062 nm. Are formed at θ = 90 degrees and φ = 23.5 degrees. The non-linear optical crystal 15 is coated with a dielectric multilayer film on both end faces in the direction of incidence and emission of laser light, and the end face on the side of the laser crystal 14 has 1062 nm as a laser fundamental wave and 531 nm as a second harmonic. And 99.9% of the transmittance%.
The end face on the laser light output side is the laser fundamental wave 10
The reflectance is 99.9% for 62 nm, and the transmittance is 98% for 631 nm, which is the second harmonic.

Next, the operation of the present embodiment will be described. The solid-state laser device 10 emits laser light from the semiconductor laser 11 in the direction of the condensing optical element 12 as shown by a broken line in FIG. The laser crystal 14 through the transparent substrate 13.

When laser light is incident on the laser crystal 14, the laser crystal 14 generates fluorescence having a center wavelength of 1062.5 nm, stimulated emission occurs in the laser resonator 16, and laser oscillation occurs.

Since the laser resonator 16 is set to confine the laser fundamental wave (1062.5 nm) in the laser resonator 16 as described above,
A high-intensity laser fundamental wave exists in the laser resonator 16. And this laser resonator 1
Numeral 6 is formed between the laser crystal 14 and the end face of the nonlinear optical crystal 15 on the laser light emission side, and the laser crystal 14 and the nonlinear optical crystal 15 are incorporated therein. Therefore, a high-efficiency second harmonic can be generated by using a high-intensity laser fundamental wave existing in the laser resonator 16, and the second harmonic can be obtained efficiently.

The laser resonator 16 has an end-pumped configuration, and the heat generated by the laser crystal 14 is generated by the energy difference between the excitation wavelength and the oscillation wavelength. A gradient occurs.
The temperature gradient in the laser crystal 14 is
However, when it is placed in the air, its heat dissipation is limited, and a refractive index distribution due to the heat is generated, and the output of the laser resonator 16 becomes unstable.

However, in the solid-state laser device 10, the optical transparent substrate 13 is placed in contact with the excitation side of the laser crystal 14, and the nonlinear optical crystal 15 is placed in contact with the laser resonator 16 side of the laser crystal 14. are doing. Therefore, the heat generated in the laser crystal 14 is
The heat is radiated efficiently in the direction parallel to the excitation direction from the portion that generates the most heat, so that the instability of the laser resonator 16 due to the heat can be reduced, and the output can be stabilized.

Further, when generating the second harmonic, the nonlinear optical crystal 15 is usually formed to have a crystal length of about 5 mm in order to achieve ease of use and downsizing. Numeral 10 indicates that the crystal length of the nonlinear optical crystal 15 is 1 mm, which is 1/5 or less of the effective crystal length.
In the conversion of the nonlinear optical crystal 15 to the second harmonic, the allowable width of the crystal angle is inversely proportional to the crystal length. That is, when the nonlinear optical crystal 15 has a crystal length of 5 mm and a crystal length of 1 mm, there is a five-fold difference in the angle allowable width. Normally, a nonlinear optical crystal 15 using a KTP crystal of about 5 mm requires alignment due to the narrow allowable width of the crystal angle. However, when the crystal length is 1 mm, only the laser crystal 14 is brought into contact. Thus, the second harmonic can be efficiently obtained.

The fundamental wave converted to the second harmonic is
This has the same effect as the internal loss, and causes a decrease in the fundamental wave intensity. However, in the solid-state laser device 10, since the crystal length of the nonlinear optical crystal 15 is set to 1 mm which is 1/5 or less of the effective crystal length, the internal loss can be reduced to 1/25, and the instability is reduced to 1/100. Thus, the output can be stabilized.

Further, the laser resonator 16 composed of the laser crystal 14 and the nonlinear optical crystal 15 is a parallel plate resonator. The shorter the resonator length is, the more the laser output is stabilized. Is formed to 1 mm or less, so that the laser output can be stabilized.

In the solid-state laser device 10, the laser crystal 14 has a crystal thickness of 0.5 mm. That is, the absorption of the excitation light (laser light) is 0.5 m
m cannot sufficiently absorb the excitation light, but since both end faces of the laser crystal 14 are coated with the dielectric multilayer film having the above-described specifications, the excitation light (laser light) is applied to the laser crystal 14 twice. The excitation light can be passed, and a sufficient passage distance can be given to the excitation light. Also,
Since the crystal thickness of the laser crystal 14 is 0.5 mm, the distribution of heat generated by the excitation light (laser light) in the crystal can be made more uniform, and the heat radiation from both end surfaces can be made more effective. Can be done. Further, by setting the crystal thickness of the laser crystal 14 to 0.5 mm, the resonator length of the laser resonator 16 can be shortened, and the output can be further stabilized.

Further, since the solid-state laser device 10 uses a micro optical element as the condensing optical element 12, the solid-state laser apparatus 10 itself can be reduced in size, and Since it is fixed to the transparent substrate 13, assembly steps such as alignment can be omitted, and costs can be reduced.

The condensing optical element 12 has a toric lens having a radius of curvature of 50 μm × 400 μm formed on the incident surface of the laser beam so that the direction of the small radius of curvature corresponds to the direction of the large divergence angle of the laser beam. Since a circular lens having a radius of curvature of 400 μm is formed on the laser light emitting surface, the laser light from the semiconductor laser 11 serving as the excitation light is emitted to the laser crystal 14 region at a radius of 120 μm.
Excitation can be performed with a spot shape that is almost circular, and the output light can also be made close to circular, so that the transverse mode quality can be further improved.

FIG. 3 shows a third embodiment of the solid-state laser device according to the present invention.
FIG. 2 is a front sectional view of a solid-state laser device 20 to which the embodiment is applied.

In the present embodiment, the solid-state laser device 10 of the second embodiment is housed in a case to improve heat dissipation. In the description of the present embodiment, The same components as those in the second embodiment are denoted by the same reference numerals, and detailed description thereof will be omitted.

In FIG. 3, the solid-state laser device 20 is
A semiconductor laser case 22 is detachably housed in the optical component case 21. The optical component case 21 and the semiconductor laser case 22 are members having good thermal conductivity.
For example, it is formed of copper.

In the semiconductor laser case 22, the same semiconductor laser 11 as in the second embodiment is provided.
The laser light is emitted inward of the optical component case 21.

In the optical component case 21, the condensing optical element 12, the optically transparent substrate 13, the laser crystal 14, and the nonlinear optical crystal 23 are arranged in this order in the optical axis direction of the laser emitted from the semiconductor laser 11. And a condensing optical element 12, an optically transparent substrate 13, and a laser crystal 14.
Is similar to that of the second embodiment.

The nonlinear optical crystal 23 is the same as the nonlinear optical crystal 15 of the first embodiment except that the aperture size is 5 mm × 5 mm. The laser crystal 14 and the nonlinear optical crystal 23 Laser crystal 14
A laser resonator 24 is formed between the laser light and the end face of the nonlinear optical crystal 23 on the laser light emission side. The laser resonator 24 has the laser crystal 14 and the nonlinear optical crystal 23 built therein.

The optical component case 21 has, on its inner surface, a holding groove into which the optical transparent substrate 13 and the non-linear optical crystal 23 are inserted at the outer peripheral end. The outer peripheral end is inserted into the holding groove, and is fixed with an adhesive having high thermal conductivity.

Then, as described above, the condensing optical element 12
Is fixed to the optical transparent substrate 13, the optical transparent substrate 13 is bonded and fixed to the laser light incident side end face of the laser crystal 14, and the nonlinear optical crystal 23 is fixed to the laser light emission side end face of the laser crystal 14. Since they are bonded and fixed, the condensing optical element 12, the optically transparent substrate 13, the laser crystal 14, and the nonlinear optical crystal 23 are
3 and the nonlinear optical crystal 23 are appropriately held in the optical component case 21 by being held in the optical component case 21.

Since the semiconductor laser case 22 is housed in the optical component case 21, the semiconductor laser 11 and the condensing optical element 12 for introducing the laser light emitted from the semiconductor laser 11 into the laser crystal 14. Can be properly aligned.

The optical component case 21 is disposed on the heat radiating plate 26 via the Peltier element 25, and the temperature is precisely adjusted by controlling the power supply to the Peltier element 25.

Next, the operation of the present embodiment will be described. The solid-state laser device 20 emits laser light from the semiconductor laser 11 in the direction of the condensing optical element 12 as shown by a broken line in FIG.
2 makes the laser beam incident from the semiconductor laser 11 incident on the laser crystal 14 through the optically transparent substrate 13.

When the laser beam enters, the laser crystal 14 generates fluorescence having a center wavelength of 1062.5 nm, stimulated emission occurs in the laser resonator 16, and laser oscillation occurs.

Since the laser resonator 24 is set so as to confine the laser fundamental wave (1062.5 nm) in the laser resonator 24 as described above,
A high-intensity laser fundamental wave exists in the laser resonator 24. And this laser resonator 2
Numeral 4 is formed between the laser crystal 14 and the end face of the nonlinear optical crystal 23 on the laser light emission side, and the laser crystal 14 and the nonlinear optical crystal 23 are incorporated therein. Therefore, a high-efficiency second harmonic can be generated using a high-intensity laser fundamental wave existing in the laser resonator 24, and the second harmonic can be obtained efficiently.

The solid-state laser device 20 has the optical transparent substrate 13 placed in contact with the excitation side of the laser crystal 14 and the laser resonator 2 of the laser crystal 14.
The non-linear optical crystal 23 is arranged in contact with the four sides.
Therefore, the heat generated in the laser crystal 14 is efficiently radiated in the direction parallel to the excitation direction from the portion generating the most heat, so that the instability of the laser resonator 24 due to the heat can be reduced and the output can be stabilized. Can be.

Further, since the solid-state laser device 20 sets the crystal length of the nonlinear optical crystal 23 to 1 mm, which is 1/5 or less of the effective crystal length, the efficiency can be improved simply by bringing the nonlinear optical crystal 23 into contact with the laser crystal 14. The second harmonic can be obtained well.

Further, in the solid-state laser device 1, since the crystal length of the nonlinear optical crystal 23 is set to 1 mm which is 1/5 or less of the effective crystal length, the internal loss can be reduced to 1/25.
The instability is reduced to 1/100, and the output can be stabilized.

Further, the laser resonator 24 composed of the laser crystal 14 and the nonlinear optical crystal 23 is a parallel plate resonator. The shorter the resonator length, the more the laser output is stabilized. Is formed to 1 mm or less, so that the laser output can be stabilized.

In the solid-state laser device 20, since the thickness of the laser crystal 14 is set to 0.5 mm, and both end surfaces thereof are coated with a dielectric multilayer film having the above-described specifications, the excitation light ( (Laser light) can be passed twice through the laser crystal 14, and a sufficient passage distance can be given to the excitation light (laser light). Further, since the crystal thickness of the laser crystal 14 is 0.5 mm, the distribution of heat generated by the excitation light (laser light) in the crystal can be made more uniform, and the heat radiation from both end faces can be further reduced. It can be done effectively. further,
By setting the crystal thickness of the laser crystal 14 to 0.5 mm, the resonator length of the laser resonator 24 can be shortened, and the output can be further stabilized.

Further, since the solid-state laser device 20 uses a micro optical element as the condensing optical element 12, the solid-state laser device 20 itself can be reduced in size, and Since it is fixed to the transparent substrate 13, assembly steps such as alignment can be omitted, and costs can be reduced.

The condensing optical element 12 has a toric lens having a radius of curvature of 50 μm × 400 μm formed on the laser light incident surface so that a direction with a small radius of curvature corresponds to a direction with a large divergence angle of the laser beam. Since a circular lens having a radius of curvature of 400 μm is formed on the laser light emission surface, the excitation light (laser light) can be excited in the laser crystal 14 region in a spot shape closer to a circular shape with a radius of about 120 μm. The output light is also close to a circle, so that the transverse mode quality can be further improved.

Furthermore, since the semiconductor laser case 22 is housed in the optical component case 21, the semiconductor laser 11 and the condensing optical element 12 for introducing the laser light emitted from the semiconductor laser 11 into the laser crystal 14. Can be properly aligned.

Further, in the solid-state laser device 20, the outer peripheral edges of the optically transparent substrate 13 and the nonlinear optical crystal 23 are held in an optical component case 21 made of copper or the like which has a high thermal conductivity and does not easily cause a temperature gradient. The heat generated in the laser crystal 14 can be more efficiently radiated, and the output can be further stabilized.

The invention made by the present inventor has been specifically described based on the preferred embodiments. However, the present invention is not limited to the above, and various modifications can be made without departing from the gist of the invention. It goes without saying that it is possible.

For example, in the second and third embodiments, the condenser optical element 12 is a quartz substrate, but the material of the condenser optical element 12 is not limited to the quartz substrate. As long as the substrate is optically transparent, an appropriate material can be used. For example, a sapphire substrate, synthetic quartz, or the like can be used. Further, the condensing optical element 12
Can be arbitrarily set.

In each of the above embodiments, Nd: LSB is used as laser crystal 5 and laser crystal 14.
Is used, but other laser crystals, for example, Nd: Y
AG, Nd: YVO ₄ , or Yb: YAG may be used.

In each of the above embodiments, the KTP crystal is used as the nonlinear optical crystal 6, the nonlinear optical crystal 15, and the nonlinear optical crystal 23.
For example, a material such as a BBO crystal, a CLBO crystal, an LBO crystal, or a KN crystal that can be phase-matched to a laser fundamental wave can be used as appropriate.

In each of the above embodiments, the sapphire crystal is used as the optically transparent substrate 4 and the optically transparent substrate 13. However, other materials such as YAG crystal and LSB crystal are used. A transparent material can be used as appropriate.

Further, the semiconductor laser 2 and the semiconductor laser 11 are not limited to those used in the above embodiments.

[0110]

According to the solid-state laser device of the first aspect of the present invention, the excitation light emitted from the excitation light source is condensed via the condensing optical system on the incident end face of the excitation light of the laser crystal. Since an optically transparent transparent substrate is brought into contact with the non-linear optical crystal at the end face of the laser crystal on the laser light emission side, a laser resonator is composed of the laser crystal and the non-linear optical crystal. The laser light can be emitted by resonating with the laser resonator, and the heat generated at the laser crystal excitation light incidence part is efficiently radiated from the transparent substrate and the nonlinear optical crystal that are in contact with both ends of the laser crystal in the excitation direction. Thus, the output can be stabilized.

According to the solid-state laser device of the second aspect of the present invention, the laser resonator is formed by using the end face of the excitation light of the laser crystal on the incident side and the end face of the nonlinear optical crystal on the emission side of the laser light. Therefore, the length of the laser resonator can be shortened, the number of parts can be reduced, and the output can be stabilized.
The solid-state laser device can be small and inexpensive.

According to the solid-state laser device of the third aspect of the present invention, the length of the nonlinear optical crystal in the optical axis direction is set to 1/5 or less of the effective crystal length, so that the number of parts of the solid-state laser device is reduced. In addition, the length of the laser resonator can be shortened, the allowable angle width of the nonlinear optical crystal can be increased five times, and the loss inside the laser resonator can be reduced to 1/25 or less. The external influence can be suppressed to 1/100 or less, that is, two digits or less, the output can be further stabilized, and the solid-state laser device can be made more compact and inexpensive. be able to.

According to the solid-state laser device of the fourth aspect of the present invention, the length of the laser crystal in the optical axis direction is less than half the absorption length of the excitation light, so that the excitation light passes through the laser crystal a plurality of times. As a configuration, it is possible to improve the absorption efficiency of the excitation light of the laser crystal, to make the heat generation in the laser crystal uniform, to improve the heat radiation efficiency, and to reduce the occurrence of heat distribution. As a result, the solid-state laser device can be made more compact and inexpensive with more stable output.

According to the solid-state laser device of the fifth aspect of the present invention, since the semiconductor laser light source is used as the excitation light source, the excitation light source can be downsized.
Excitation can be performed efficiently, and the solid-state laser device can be made smaller and more efficient.

According to the solid-state laser device of the sixth aspect of the present invention, an optical element having a curved shape formed on a predetermined optically transparent substrate is used as a focusing optical system.
A compact and highly efficient solid-state laser device that can reduce the size of the condensing optical system and improve the transverse mode quality by exciting the laser crystal with a small and nearly circular spot diameter. It can be.

According to the solid-state laser device of the present invention, since the optical element as the light-collecting optical system is fixed to the transparent substrate, alignment can be facilitated, and the solid-state laser device can be further improved. It can be cheaper.

According to the solid-state laser device of the present invention, the transparent substrate and the nonlinear optical crystal are housed in a predetermined case, and the outer peripheral end thereof is in contact with the inside of the case. Heat generated in the excitation light incident portion of the crystal can be efficiently radiated to the case from the transparent substrate and the nonlinear optical crystal that are in contact with both end surfaces in the excitation direction of the laser crystal, and the output can be further stabilized. .

According to the ninth aspect of the present invention, since the transparent substrate is formed of a sapphire substrate, the transmittance of the excitation light is set to 99.9% or more and the thermal conductivity of the laser crystal is increased. It can be increased to about 4 to 10 times, and the heat radiation can be further improved, and the birefringence is reduced, so that the solid-state laser device has higher efficiency and more stable output. be able to.

[Brief description of the drawings]

FIG. 1 is a front view of a solid-state laser device to which a first embodiment of a solid-state laser device according to the present invention is applied.

FIG. 2 is a front view of a solid-state laser device to which a second embodiment of the solid-state laser device according to the present invention is applied.

FIG. 3 is a front sectional view of a solid-state laser device to which a third embodiment of the solid-state laser device according to the present invention is applied.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Solid-state laser apparatus 2 Semiconductor laser 3 Condensing optical system 4 Optically transparent substrate 5 Laser crystal 6 Nonlinear optical crystal 7 Laser resonator 10 Solid-state laser apparatus 11 Semiconductor laser 12 Condensing optical element 13 Optically transparent substrate 14 Laser crystal 15 Non-linear Optical crystal 16 Laser resonator 20 Solid-state laser device 21 Optical component case 22 Semiconductor laser case 23 Nonlinear optical crystal 24 Laser resonator 25 Peltier element 26 Heat sink

Claims (9)

[Claims] 1. An excitation light emitted from a predetermined excitation light source,
In a solid-state laser device that converges on a laser crystal disposed in a laser resonator with a predetermined condensing optical system to excite the laser crystal and resonates with the laser resonator to emit laser light, A predetermined optically transparent substrate is brought into contact with an end face of the crystal on the incident side of the excitation light, and a predetermined nonlinear optical crystal is brought into contact with an end face of the laser crystal on the emission side of the laser light. Characterized solid-state laser device. 2. The laser resonator according to claim 1, wherein the laser resonator is formed using an end face of the laser crystal on an incident side of the excitation light and an end face of the nonlinear optical crystal on an emission side of the laser light. The solid-state laser device according to claim 1. 3. The solid-state laser device according to claim 1, wherein the length of the nonlinear optical crystal in the optical axis direction is one fifth or less of the effective crystal length. 4. The solid-state laser device according to claim 1, wherein the length of the laser crystal in the optical axis direction is not more than half of the absorption length of the excitation light. . 5. The solid-state laser device according to claim 1, wherein said excitation light source is a semiconductor laser light source. 6. The optical system according to claim 1, wherein the condensing optical system is an optical element having a curvature shape formed on a predetermined optically transparent substrate. Solid laser device. 7. The solid-state laser device according to claim 6, wherein said optical element is fixed to said transparent substrate. 8. The apparatus according to claim 1, wherein the transparent substrate and the nonlinear optical crystal are housed in a predetermined case, and an outer peripheral end thereof is in contact with the inside of the case. 8. The solid-state laser device according to any one of 7. 9. The solid-state laser device according to claim 1, wherein said transparent substrate is a sapphire substrate.