JPH0645680A - Solid state laser - Google Patents

Abstract

PURPOSE:To obtain a solid state laser which can efficiently oscillate a harmonic laser light such as a green light of a second harmonic wave of a fundamental laser light of an Nd:YAG laser light, etc. CONSTITUTION:A nonlinear optical crystal 12 having properties to generate a fundamental wave laser light L1 by itself upon irradiation with an exciting light L0 from an exciting light source 4 and to generate a harmonic laser light L2 of the light L1, and a beam splitter 13 for passing the light L1 generated from the crystal 12 and reflecting the light L2 to externally output it are disposed in a laser resonator commonly with an optical axis thereby to externally output the light L1 without passing other optical component disposed in the resonator to reduce loss and beam quality deterioration and to decrease the number of components, thereby efficiently obtaining the light L2 of high quality with less number of components.

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 which uses a nonlinear optical crystal to generate a laser beam as a harmonic of a fundamental wave laser beam.

[0002]

2. Description of the Related Art As a solid-state laser device for generating a laser beam as a harmonic of a fundamental laser beam by using a nonlinear optical crystal, the device shown in FIGS. 2 and 3 has been conventionally proposed.

In the example shown in FIG. 2, a laser medium 1, a non-linear optical crystal 2 and a wavelength selective mirror 3 are arranged with their optical axes in common, and the mirror 3 and the laser medium 1 are attached to the left end face thereof. A laser resonator is configured with the wavelength-selective mirror 1 a having a multilayer film, and the pumping light L ₀ emitted from the semiconductor laser device 4 to the laser medium 1 is collected by the condenser lens 5.
Through the end face of the laser medium 1 to excite the end face of the laser medium ₁ to generate the fundamental wave laser beam L _{1 and} the non-linear optical effect when the fundamental wave laser beam L ₁ passes through the non-linear optical crystal 2. The harmonic laser beam L ₂ is generated and taken out through the mirror 3.

Here, Nd: YAG is used as the laser medium 1.
A laser medium (oscillation wavelength; 1.062 μm) was used, and a KTP (KTiOPO ₄ ) crystal (T
In order to obtain the second harmonic laser light (wavelength: 0.531 μm) that is green light using YPE2), the nonlinear optical crystal 2
Between the mirror 3 and the mirror 3, a λ / 4 plate 6 for satisfying the phase matching condition of the nonlinear optical crystal 2 is arranged, and the fundamental wave laser beam L _{1 is set} to the single longitudinal mode to obtain the first longitudinal mode. Two
The etalon 7 is arranged to obtain the harmonic laser beam L ₂ . In this case, an AlGaAs semiconductor laser device that oscillates a laser beam L ₀ having a wavelength of 0.8 μm that can efficiently excite the Nd: YAG laser medium is used as the semiconductor laser device 4 as the excitation light source.

The wavelength-selective multilayer mirror 1a is
Light of 0.8 μm wavelength is transmitted well, while wavelength of 1.06
It reflects light of 2 μm and light of wavelength 0.531 μm. The wavelength-selective mirror 3 reflects light having a wavelength of 1.062 μm and transmits light having a wavelength of 0.531 μm well.

In the example shown in FIG. 2, a Q switch element 8 is provided instead of the etalon 6 in the example shown in FIG.
The configuration is the same as that shown in FIG. 1 except that the pulsed laser light L ₂ is obtained by Q-switch oscillation. As the Q switch element 8, for example, an acousto-optic element or the like is used.

[0007]

By the way, in the above-mentioned conventional solid-state laser device, the harmonic laser light L ₂ passes through the etalon 6 or the Q switch element 8 arranged in the resonator and then is emitted to the outside. Is ejected. Therefore, the harmonic laser light L ₂ inevitably passes through the etalon 6 or the Q switch element 8 and suffers loss and deterioration of the quality of the radiation.

Further, since the number of optical components arranged in the resonator is large, the loss in each component and the loss due to the reflection of the input / output end face of each component also increase in proportion to this, and the loss due to this. Can no longer be ignored. Further, an antireflection film or the like is provided on each end face in order to reduce this loss as much as possible, but this further increases the substantial number of parts, which is also disadvantageous in terms of life, reliability, manufacturing cost, and the like. Furthermore, there is a disadvantage that the device cannot be formed in a small size due to the large number of parts.

The present invention has been made under the above-mentioned background, and it is possible to reduce loss in the resonator and the number of parts to efficiently oscillate a harmonic laser beam. At the same time, it is an object of the present invention to provide a solid-state laser device which is advantageous in terms of life, reliability and manufacturing cost.

[0010]

The present invention has solved the above-mentioned problems by adopting the following configuration.

(1) In a solid-state laser device for generating a laser beam as a harmonic laser beam of a fundamental wave laser beam by using a non-linear optical crystal, by irradiating a pumping light emitted from a pumping light source, the laser beam is fundamentally generated by itself. A nonlinear optical crystal having the property of generating a wave laser beam and a harmonic of this fundamental laser beam, and the fundamental laser beam generated in the nonlinear optical crystal is transmitted and the harmonic laser beam is reflected to the outside. The beam splitter to be extracted and the optical axis are arranged in common in the laser resonator.

(2) In the solid-state laser device according to Structure 1, a structure is characterized in that an etalon tuning element is arranged in the laser resonator with the optical axis in common with the nonlinear optical crystal and the beam splitter.

(3) In the solid-state laser device of Structure 1, a Q switch element is arranged in the laser resonator with the optical axis in common with the nonlinear optical crystal and the beam splitter.

(4) In the solid-state laser device according to any one of configurations 1 to 3, the nonlinear optical crystal is NY.
AB (Nd _x Y _1-x Al ₃ (BO ₃ ) ₄ ) and the excitation light source is a semiconductor laser device.

[0015]

According to the structure 1, the fundamental wave laser light generated in the nonlinear optical crystal passes through the beam splitter, resonates, and oscillates. On the other hand, at the same time, the harmonic laser light generated in the nonlinear optical crystal is reflected by the beam splitter and immediately taken out. Therefore, the harmonic laser light is taken out to the outside without passing through other optical parts such as the etalon and the Q switch element arranged in the resonator, and it is possible to avoid the loss and the deterioration of the radiation quality due to this. .

Further, since the oscillation of the fundamental wave laser light and the generation of the harmonic wave laser light are performed by one nonlinear optical crystal, the number of parts can be reduced.

According to the structure 2, a single longitudinal mode harmonic laser beam can be obtained, and according to the structure 3, a harmonic pulsed laser beam by the Q switch can be obtained.

According to the structure 4, a good quality green laser light can be efficiently obtained.

[0019]

(First Embodiment) FIG. 1 is a view showing the arrangement of a solid-state laser device according to the first embodiment of the present invention. Hereinafter, the first embodiment will be described in detail with reference to FIG. Since this embodiment has many parts in common with the conventional example shown in FIG. 2 described above, common parts are designated by the same reference numerals, and description of common points is omitted. The description will be centered on points peculiar to the embodiment.

The difference between this embodiment and the conventional example shown in FIG. 2 is that a nonlinear optical crystal 12 is arranged in place of the laser medium 1 in FIG. 2 and the nonlinear optical crystal 2 in FIG. 2 is removed. In addition, the λ / 4 plate 6 in FIG.
The point is that the beam splitter 13 is arranged instead of.
Other configurations are the same as those shown in FIG.

The nonlinear optical crystal 12 itself emits the fundamental wave laser light L ₁ by irradiating it with the excitation light L ₀ containing the light having a wavelength of 0.8 μm, and at the same time, the second fundamental wave laser light L ₁ is emitted. It has a property of generating a laser beam L ₂ that is a harmonic wave. In this embodiment, NYAB (Nd
TYPE _{1 of x} Y _1-x Al ₃ (BO ₃ ) ₄ ) crystal was used. That is, the fundamental wave laser light L having a wavelength of 1.062 μm
_The phase matching angle θm is set to 3 so that phase matching can be achieved between ₁ and its second harmonic light (green light) having a wavelength of 0.531 μm.
It is set to 2 ° 54 '. The size of this crystal is 3
It is × 3 × 5 mm, and the optical path length is 5 mm. Also, N
The concentration of d ions is 3.5 atomic%. In this case, TY
In the nonlinear optical crystal of PE1, the polarization plane of the fundamental wave laser light L ₁ becomes a plane including the O axis direction by aligning the polarization plane of the excitation light L ₀ with the ordinary ray refractive index (O) axis direction of the crystal, It is possible to obtain the P-polarized fundamental wave laser light L ₁ . In that case, the second harmonic laser beam L ₂ becomes S-polarized.

A mirror 12a made of a dielectric multilayer film is attached to the left end surface of the nonlinear optical crystal 12 in the figure.
The mirror 12a constitutes a laser resonator with the mirror 3 and transmits the pumping light L ₀ having a wavelength of 0.8 μm well, but the fundamental laser light L ₁ having a wavelength of 1.062 μm and the wavelength 0.531 μm. It has a property of reflecting the second harmonic laser beam L ₂ of. In this embodiment, this mirror 12a
As is the transmittance for the excitation light L ₀ of wavelength 0.8μm is 98%, the second harmonic laser beam L ₂ of the fundamental laser beam L ₁ and the wavelength 0.531μm wavelength 1.062μm
A dielectric multilayer film having a reflectance of 99% or more was used.

The right end face 1 in the figure of the nonlinear optical crystal 12
An antireflection film made of a dielectric multilayer film is formed on 2b, and a fundamental wave laser beam L ₁ having a wavelength of 1.062 μm and a second harmonic laser beam L having a wavelength of 0.531 μm are formed on the end face 12b.
_The transmittance for ₂ and 99 is 99% or more.

The beam splitter 13 is formed by forming a dielectric multilayer film on the surface of a light-transmitting thin plate, and transmits only the P-polarized component and the S-polarized component on the surface 13a facing the nonlinear optical crystal 12. A dielectric multi-layer film having a property of reflecting light is formed, and this surface 13a is approximately 45 with respect to the optical axis of the laser resonator.
° It is arranged so as to make an egg. Therefore, the P-polarized fundamental laser light L ₁ can pass through the beam splitter 13, but the S-polarized second harmonic laser light L ₂ is reflected and taken out. The back surface 13b is provided with an antireflection multilayer film which transmits 99% or more of the laser beams L ₁ and L ₂ .

The semiconductor laser device 4 has a wavelength of 0.8.
Any device capable of emitting a laser beam of μm with an output of about several hundred mW may be used (as such a semiconductor laser device,
For example, Broad Area SL manufactured by Sony Corporation
D303WT; output is 500mW, etc.). Although the convex lens is used as the condenser lens 5 in the present embodiment, a plurality of lenses may be combined, or an aspherical lens or a cylindrical lens may be used.

The mirror 3 is formed by forming a light-transmitting member in the shape of a concave lens and forming a dielectric multilayer film 3a on the concave surface to form a reflecting surface. The reflectance of this reflecting surface is a wavelength of 1.062 μm.
With respect to the fundamental wave laser beam L ₁ of 99% or more. The curvature of the concave surface is determined by a known method so as to form an optimum resonator, but in this embodiment, the resonator length (distance between the mirror 3 and the mirror 12a) is set to 50 mm in optical length, and the concave surface is formed. Has a radius of curvature of 50 mm. The FSR (free spectral range) of the laser resonator at this time is 3 GHz. Further, the spatial mode of the fundamental wave laser light L ₁ is close to TEM ₀₀ , and a stable output can be obtained.

The etalon 7 is a fused sil
ica (refractive index for the fundamental wave laser beam L ₁ having a wavelength of 1.062 μm; 1.54) is formed to a thickness of 1.5 mm, and a coating having a reflectance of 90% for the fundamental wave laser beam L _{1 is} provided on both surfaces. What was done was used. FSR at this time is about 6
It is 5 GHz and the reflectance finesse Fr is 30.

By the insertion of the etalon 7, the fundamental wave laser light L ₁ becomes a single longitudinal mode, and therefore the second harmonic laser light L ₂ also becomes a single longitudinal mode.

According to the first embodiment described above, since the fundamental laser light L ₁ generated in the nonlinear optical crystal 12 is P-polarized light, it passes through the beam splitter 13 to resonate and oscillate. On the other hand, at the same time, the second harmonic laser light L ₂ generated in the nonlinear optical crystal 12 is S-polarized, so that the beam splitter 1
It is reflected by 3 and immediately taken out. Therefore, the second harmonic laser light L ₂ is extracted to the outside without passing through the etalon 7 arranged in the resonator, so that the loss and the deterioration of the radiation quality due to the extraction can be avoided. Therefore,
The second harmonic laser light L ₁ (green light) of good quality can be efficiently extracted.

Further, the oscillation of the fundamental wave laser light L ₁ and the generation of the second harmonic laser light L ₂ are combined into one nonlinear optical crystal 12
Since the number of components is smaller than that of the conventional example shown in FIG. 2, the oscillation efficiency can be increased correspondingly, and it is also advantageous in terms of life, reliability, and manufacturing cost. Become.

(Second Embodiment) FIG. 4 is a view showing the arrangement of a solid-state laser device according to the second embodiment of the present invention. In this embodiment, a Q switch element 18 is arranged instead of the etalon 7 in the first embodiment shown in FIG. 1 to perform Q switch oscillation of the fundamental wave laser light L ₁ .
Except for obtaining the pulsed second harmonic laser beam L2, it has the same configuration as that of the first embodiment.

In this embodiment, an acousto-optic modulator is used as the Q switch element 18. In this case, a flint glass (FD-6 manufactured by HOYA Co., Ltd.), which is transparent to the fundamental wave laser beam L ₁ and has a high refractive index, is adopted as the acousto-optic medium forming the acousto-optic modulator. The Q switch element 18 is driven by applying an ultrasonic wave having a frequency of 80 MHz by a control device (not shown). As this control device, for example, a control device that can arbitrarily set the switching frequency between DC and 50 KHz can be used. The Q switch element 18 may include a temperature control element 1 such as a Peltier element, if necessary.
8a is attached to stabilize the operation.

In this embodiment, the Q switch element 18
When the switching frequency of 1 is set to 1 kHz, the pulsed fundamental wave laser light L ₁ having a pulse width of about 30 nsec is oscillated, whereby the second harmonic laser light L ₂ having a high peak power is obtained. According to this embodiment, the second
The harmonic laser light L ₂ is extracted to the outside without passing through the acousto-optic modulator 18 arranged in the resonator, and it is possible to avoid the loss and the deterioration of the wire quality due to this. Therefore, the high-quality second harmonic laser light L ₁ (green light) can be efficiently extracted. Further, the number of parts is smaller than that of the conventional example shown in FIG. 3, and therefore, the oscillation efficiency can be increased correspondingly, and it is also advantageous in terms of life, reliability, and manufacturing cost.

In each of the above embodiments, an example using a NYAB crystal as the non-linear optical crystal is given.
Other non-linear optical crystals include, for example, EYAB (E
r _X Y _1-X A ■ ₃ (BO ₃ ) ₄ ), Nd: MgO: Li
NbO ₃ , Nd: KTP, Nd: KDP, Nd: BB
O, Nd: LBO, Nd: KNbO ₃ or the like can be used.

Further, although the example in which the semiconductor laser device is used as the excitation light source to perform the end face excitation, another laser device may be used instead of the semiconductor laser device, and a semiconductor laser array or a flash lamp. It is also possible to use side-effect excitation using, for example.

Further, as the Q switch element, another Q switch element such as a Pockels element may be used.

[0037]

As described above in detail, according to the present invention, the fundamental wave laser light is generated by itself by irradiating the exciting light emitted from the exciting light source and the harmonics of the fundamental wave laser light are generated. A non-linear optical crystal having the property of generating,
By arranging a beam splitter that transmits the fundamental laser light generated in the nonlinear optical crystal and reflects the harmonic laser light and extracts the reflected laser light to the outside in the laser resonator with the optical axis in common, the harmonic laser light Is taken out to the outside without passing through other optical parts arranged in the resonator to reduce loss and deterioration of radiation quality, and to oscillate the fundamental laser light and generate the harmonic laser light. By using two nonlinear optical crystals, the number of parts can be reduced and high-quality harmonic laser light can be efficiently obtained.

[Brief description of drawings]

FIG. 1 is a diagram showing a configuration of a solid-state laser device according to a first embodiment of the present invention.

FIG. 2 is a diagram showing a configuration of a conventional example.

FIG. 3 is a diagram showing a configuration of a conventional example.

FIG. 4 is a diagram showing a configuration of a solid-state laser device according to a second embodiment of the present invention.

[Explanation of Codes] 1 laser medium 2,12 nonlinear optical crystal 3,12a mirror 4 semiconductor laser device 5 condenser lens 6 λ / 4 plate 7 etalon 8,18 optical Q switch element 13 beam splitter L ₁ fundamental wave laser light L2 Harmonic laser light

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[Procedure amendment]

[Submission date] October 14, 1991

[Procedure Amendment 1]

[Document name to be amended] Statement

[Correction target item name] 0004

[Correction method] Change

[Correction content]

Here, Nd: YAG is used as the laser medium 1.
A laser medium (oscillation wavelength; 1.062 μm) was used, and a KTP (KTiOPO ₄ ) crystal (T
When the second harmonic laser light (wavelength: 0.531 μm) that is green light is obtained using the YPE2, the phase matching condition of the nonlinear optical crystal 2 is satisfied between the nonlinear optical crystal 2 and the mirror 3. λ / 4 plate 6 is placed (OPTICS LET
TERS October 1988 Vol.13, No.10 P806 See Fig3),
Further, an etalon 7 is arranged in order to convert the fundamental wave laser light L ₁ into a single longitudinal mode to obtain the second harmonic laser light L ₂ in the single longitudinal mode. In this case, the semiconductor laser device 4 serving as a pumping light source oscillates a laser beam L ₀ having a wavelength of 0.8 μm capable of efficiently pumping the Nd: YAG laser medium.
An lGaAs semiconductor laser device is used.

[Procedure Amendment 2]

[Document name to be amended] Statement

[Correction target item name] 0006

[Correction method] Change

[Correction content]

In the example shown in FIG. 3, a Q switch element 8 is provided instead of the etalon 7 in the example shown in FIG.
The structure is the same as that shown in FIG. 2 except that the pulsed laser light L2 is obtained by Q-switch oscillation. As the Q switch element 8, for example, an acousto-optic element or the like is used. (OPTICS LETTERS June 1988 Vol.13, No.
(Refer to 6)

[Procedure 3]

[Document name to be amended] Statement

[Correction target item name] 0026

[Correction method] Change

[Correction content]

The mirror 3 is formed by forming a light-transmitting member in the shape of a concave lens and forming a dielectric multilayer film 3a on the concave surface to form a reflecting surface. The reflectance of this reflecting surface is a wavelength of 1.062 μm.
With respect to the fundamental wave laser beam L ₁ of 99% or more. The curvature of the concave surface is determined by a well-known method so as to form an optimum resonator, but in this embodiment, the resonator length (the distance between the dielectric multilayer film 3a of the mirror 3 and the mirror 12a) is optically determined. The length is 50 mm, and the radius of curvature of the concave surface is 50 mm. FS of laser resonator at this time
R (free spectral range) is 3 GHz. Further, the spatial mode of the fundamental wave laser light L ₁ is close to TEM ₀₀ , and a stable output can be obtained.

Claims (4)

[Claims] 1. A solid-state laser device for generating laser light as harmonic light of fundamental-wave laser light using a non-linear optical crystal, by irradiating with excitation light emitted from an excitation light source the fundamental-wave laser light itself. And a non-linear optical crystal having the property of generating harmonics of the fundamental laser light, and a beam splitter for transmitting the fundamental laser light generated in the nonlinear optical crystal and reflecting the harmonic laser light to the outside. A solid-state laser device in which the optical axes are arranged in common in the laser resonator. 2. The solid-state laser device according to claim 1, wherein an etalon tuning element is arranged in the laser resonator with the optical axis being common to the nonlinear optical crystal and the beam splitter. . 3. The solid-state laser device according to claim 1, wherein a Q switch element is arranged in the laser resonator with the optical axis in common with the nonlinear optical crystal and the beam splitter. . 4. The solid-state laser device according to claim 1, wherein the nonlinear optical crystal is NYA.
B (Nd _x Y _1-x Al ₃ (BO ₃ ) ₄ ), wherein the excitation light source is a semiconductor laser device.