JP2000347235A - Solid laser device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent decrease in the output due to mismatching of phases between the wavelength converted waves exiting from a nonlinear optical crystal and then reflected by a mirror to return the optical path and the wavelength converted waves exiting from the nonlinear optical crystal to the other direction in the process of wavelength conversion of oscillated beams by the nonlinear optical crystal. SOLUTION: In this device, two kinds of wavelength converted waves 19 exit from a nonlinear optical crystal 16 in the opposite directions to each other, and the device is equipped with a mirror (consisting of, for example, the end face 13a of a solid laser medium 13) which regularly reflects the wavelength converted waves 19 exiting in one direction. In this method, at least one optical member through which the wavelength converted waves 19 pass is disposed between the nonlinear optical crystal 16 and the mirror, and the refractive index of the optical member is changed by controlling the temp. or the like of the optical member by a phase controlling part 40.

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 having a wavelength conversion function, and more particularly, to a wavelength-converted wave that is emitted from a nonlinear optical crystal in one direction and then reflected by a mirror and turned back. The present invention relates to a solid-state laser device that prevents a decrease in output due to a phase shift between a wavelength-converted wave emitted in another direction.

[0002]

2. Description of the Related Art As disclosed in, for example, Japanese Patent Application Laid-Open No. 62-189783, a solid-state laser device for exciting a solid-state laser medium to which neodymium (Nd) is added by light emitted from a semiconductor laser or the like has been known. I have. This type of solid-state laser device basically includes a solid-state laser medium, an excitation source for exciting the solid-state laser medium, and a resonator.

In this solid-state laser device, in order to obtain a laser beam with a shorter wavelength, a nonlinear optical crystal is arranged in the optical path of the laser beam reciprocating in the resonator, and the laser beam is converted to a second harmonic or the like. Wavelength conversion is also widely performed.

In the solid-state laser device having this wavelength conversion function, a wavelength-converted wave such as a second harmonic is emitted from the nonlinear optical crystal in directions opposite to each other as indicated by A and B in FIG. In FIG. 8, 1 is a solid-state laser medium (laser crystal), 2 is a nonlinear optical crystal, and 3 is a resonator mirror. 4 is a Brewster plate for controlling polarization, and 5 is an etalon for making a single longitudinal mode.

In the example shown in FIG. 8, the output direction of the wavelength-converted wave A is the output direction. The wavelength-converted wave B emitted in the opposite direction is specularly reflected by a mirror, and is superimposed on the wavelength-converted wave A and output. It is supposed to be. In this case, the above-mentioned mirror is provided with a wavelength-converted wave B on the outer end face 1a of the solid-state laser medium 1.
Is formed by applying a high-reflection coating.

[0006]

However, as described above, when one of the two types of wavelength-converted waves emitted in the opposite directions from the nonlinear optical crystal is specularly reflected and is output while being superimposed on the other wavelength-converted wave. In some cases, the two phases are shifted from each other and weaken each other. Therefore, in the conventional solid-state laser device having the wavelength conversion function, there is a large individual difference in the output of the wavelength-converted wave, and there is a case where a desired output cannot be obtained in a high ratio.

Accordingly, the present invention provides an output reduction due to a phase shift between a wavelength-converted wave emitted from the nonlinear optical crystal in one direction and reflected by a mirror and turned back, and a wavelength-converted wave emitted from the nonlinear optical crystal in the other direction. It is an object of the present invention to provide a solid-state laser device capable of preventing the problem.

[0008]

A solid-state laser device according to the present invention is capable of adjusting the phase of a wavelength-converted wave by controlling the refractive index of an optical component through which the wavelength-converted wave reflected by a mirror passes. , And a phase shift between the wavelength-converted waves superimposed on the wavelength-shifted waves is eliminated or reduced.

More specifically, a solid-state laser device according to the present invention comprises a solid-state laser medium, an excitation source for exciting the solid-state laser medium, a resonator, and a laser beam as a fundamental wave reciprocating in the resonator. A nonlinear optical crystal arranged in the optical path for wavelength-converting the laser beam, and a wavelength-converted wave emitted in one direction out of two types of wavelength-converted waves emitted from the nonlinear optical crystal in opposite directions. A solid-state laser device including a mirror for controlling the refractive index of at least one optical component through which the wavelength-converted wave passes between the nonlinear optical crystal and the mirror. .

As means for controlling the refractive index of the optical component, for example, means for controlling the temperature of the optical component is applicable. As such a temperature control means, a means for controlling the temperature of the solid-state laser medium can be used. In the case where the nonlinear optical crystal has a region having a periodic domain inversion structure and a region having no periodic domain inversion structure, the temperature control means may include a means for controlling the temperature of the nonlinear optical crystal. Can also be used.

On the other hand, when the optical component is a crystal having an electro-optical effect, means for applying a voltage to the crystal can be applied as means for controlling the refractive index.

In the solid-state laser device according to the present invention, the wavelength conversion wave emitted from the non-linear optical crystal in the direction opposite to the one direction and the specularly reflected wavelength conversion wave superposed on the wavelength conversion wave. It is desirable that the phase shift be kept within ± π / 2.

[0013]

According to the solid-state laser device of the present invention, there is provided means for controlling the refractive index of the optical component through which the wavelength-converted wave reflected by the mirror passes.
By controlling this refractive index, it is possible to adjust the phase of the wavelength converted wave that is folded back.

If this is the case, no matter what the phase relationship between the two types of wavelength converted waves is in a state where the refractive index is not controlled, the phase of the folded wavelength converted wave is
Match the phase of the wavelength conversion wave emitted directly in the output direction,
Or it can be adjusted to a state close to it,
The output of the wavelength-converted wave after the superposition can be sufficiently increased.

[0015]

Embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 1 shows a side view of a semiconductor laser pumped solid-state laser device according to a first embodiment of the present invention.

This solid-state laser device includes a semiconductor laser 11 for emitting a laser beam 10 as excitation light, a condensing lens 12 for condensing a laser beam 10 as divergent light, and a solid-state laser doped with neodymium (Nd). A YAG crystal (Nd: YAG crystal) 13 as a medium, and the Nd: YAG crystal 13
And a resonator mirror 14 arranged on the front side, that is, on the side opposite to the semiconductor laser 11.

The Nd: YAG crystal 13 and the resonator mirror 14
Between the Nd: YAG crystal 13 side and the phase control unit 40, the Brewster plate 15, and MgO-doped LiN which is a nonlinear optical material having a periodic domain inversion structure.
bO ₃ crystal (hereinafter referred to as inverted domain LN crystal) 1
6.Etalon 17 made of quartz plate tilted 35 'to the optical axis
Are arranged.

Further on the front side of the resonator mirror 14, there is provided a partial reflection mirror 25 for partially branching a second harmonic 19 emitted as described later. The second harmonic 19 branched here is detected by a photodetector 26 such as a photodiode.

The semiconductor laser 11 is a broad area laser having an active layer width of about 50 μm and emits a laser beam 10 having a wavelength of 808 nm. Also condensing lens
Reference numeral 12 denotes, for example, a gradient index lens (trade name: Selfoc lens), which emits a laser beam 10 of Nd: YA.
Light is condensed so as to converge inside the G crystal 13. The condenser lens 12 and the semiconductor laser 11 are fixed to a holding member 20. Hereinafter, the portion fixed to the holding member 20 is referred to as an excitation unit.

On the other hand, the portion from the Nd: YAG crystal 13 to the resonator mirror 14 is fixed to another holding member 21.
Hereinafter, the portion fixed to the holding member 21 is referred to as a resonator portion.

The partial reflection mirror 25 and the photodetector 26 are fixed to another holding member 22. Hereinafter, the portion fixed to the holding member 22 is referred to as an APC portion.

The above-described excitation unit, resonator unit, and AP
The holding members 20, 21 and 22, each holding the C portion, are adhered on a plate-shaped base plate 30, and the base plate
It is fixed to a package base 32 via 30 and a Peltier element 31. And the emission window is on the package base 32
A package cap 34 having 34a is attached thereto, and both of them define a space that is kept airtight from the outside. The portion above the Peltier element 31 is housed in this space.

The Nd: YAG crystal 13 emits light having a wavelength of 946 nm when neodymium ions are excited by the incident laser beam 10. On the incident end face 13a of the Nd: YAG crystal 13, light having a wavelength of 946 nm is favorably reflected (reflectance is 99.9% or more), while an excitation laser beam 10 having a wavelength of 808 nm is favorably transmitted (transmittance is 93% or more). Coated. On the other hand, the mirror surface 14a of the resonator mirror 14 is provided with a coating that reflects light having a wavelength of 946 nm well (reflectance of 99.9% or more) and transmits light of the following wavelength 473 nm (transmittance of 90% or more). I have.

Then, the light having the wavelength of 946 nm is confined between the Nd: YAG crystal end face 13a and the mirror face 14a, which is a highly reflecting surface for the light, to cause laser oscillation, and the laser beam 18 having the wavelength of 946 nm is generated. I do. The laser beam 18 as a fundamental wave is converted by the inversion domain LN crystal 16 into a second harmonic 19 having a wavelength of す な わ ち, ie, 473 nm, and the second harmonic 19 is mainly emitted from the resonator mirror 14. The second harmonic 19 is partially branched by the partial reflection mirror 25, and then passes through the exit window 34a and exits outside the package cap 34.

Here, the Brewster plate 15 has a wavelength of 946 nm.
The laser beam 18 is arranged at a Brewster angle and controls the polarization direction of the laser beam 18. The etalon 17 is formed to have a thickness of 0.38 mm, and converts the laser beam 18 into a single longitudinal mode.

On the other hand, the above-described periodic domain inversion structure formed in the inversion domain LN crystal 16 is based on the Brewster plate.
The temperature of the laser beam 18 whose polarization direction is defined by 15
The period of the domain inversion unit is set to about 4 μm so that the second harmonic 19 is efficiently converted at 25 ° C.

The coating formed on the incident end face 13a of the Nd: YAG crystal 13 is a second harmonic having a wavelength of 473 nm.
19 is designed to reflect well (with a reflectivity of 95% or more). From the inversion domain LN crystal 16, the second harmonic 19 is emitted in the output direction, that is, toward the resonator mirror 14, and
In the opposite direction, ie, on the Nd: YAG crystal 13 side, a second
The harmonic 19 is emitted. The second harmonic 19 emitted in the latter direction is specularly reflected on the coated Nd: YAG crystal end face 13a and turned back, and is superimposed on the second harmonic 19 emitted in the former direction and output. .

In this embodiment, the temperature inside the resonator is detected by the thermistor 36 attached to the resonator.
The drive current of the Peltier device 31 is adjusted by the first temperature control circuit 37 so that the detected temperature becomes a predetermined temperature,
The temperature in the resonator is maintained at a predetermined temperature.

The semiconductor laser 11 is generally made of an APC (Au
Receives constant output control called tomatic power control. That is, the second harmonic 19 partially branched by the partial reflection mirror 25 of the APC unit is monitored by the photodetector 26, and the output of the photodetector 26 is output to the LD current control circuit.
Entered in 38. The LD current control circuit 38 controls the drive current of the semiconductor laser 11 so that the monitor light amount indicated by the output becomes constant, and as a result, the output of the second harmonic 19 is kept constant.

In order to put the second harmonic 19 into practical use,
Generally, a filter that absorbs the laser beam 10 emitted in the same direction and the laser beam 18 as a fundamental wave is required, but such a filter may be provided in the APC section.

Next, the point that the phase of the second harmonic 19 that is specularly reflected at the end face 13a of the Nd: YAG crystal and turned back and the phase of the second harmonic 19 that is emitted directly in the output direction will be described. FIG.
Shows in detail the configuration of the phase control unit 40 disposed in the resonator unit, and will be described below with reference to FIG. The phase control unit 40 is a quartz plate fixed to the holding member 21 of the resonator unit.
41, a MgO-doped LiNbO ₃ crystal (hereinafter referred to as MgO: LN crystal) 42 fixed on the quartz plate 41, and a metal block 43 fixed on the MgO: LN crystal 42. The Peltier device 45 includes a thermistor 44 attached to the metal block 43, a Peltier element 45 fixed on the metal block 43, and a heat sink 46 fixed on the Peltier element 45.

The MgO: LN crystal 42 does not have a periodic domain inversion structure, and is formed with a length of 1 mm and a thickness of 0.4 mm. The MgO: LN crystal 42 is arranged on the optical path of the second harmonic 19 emitted from the inversion domain LN crystal 16 to the Nd: YAG crystal 13 side. This MgO:
The LN crystal 42 is arranged such that the c-axis direction of the crystal coincides with the linearly polarized light directions of the laser beam 18 and the second harmonic 19 as the fundamental waves.

The quartz plate 41 disposed between the MgO: LN crystal 42 and the holding member 21 has a very low thermal conductivity. Therefore, the temperature of the MgO: LN crystal 42 can be controlled by the Peltier element 45 via the metal block 43 independently of the temperature of the resonator section. This temperature adjustment is performed by detecting the temperature of the metal block 43 at which the temperature becomes substantially the same as that of the MgO: LN crystal 42 by the thermistor 44, and by the second temperature control circuit 39, the Peltier element 45 is adjusted so that the detected temperature becomes a desired value.
This is done by adjusting the drive current.

As described above, when the temperature of the MgO: LN crystal 42 is changed, its refractive index changes. Therefore, after passing through the crystal 42, the second harmonic wave 19 which is specularly reflected at the end face 13a of the Nd: YAG crystal and turned back. Changes. So this second
The phase of the harmonic 19 and the second harmonic 19 superimposed thereon (the second harmonic 19 emitted directly to the side of the resonator mirror 14) are matched so that they are strengthened with each other, and the maximum second harmonic 19 Wave output can be obtained.

When controlling the temperature of the MgO: LN crystal 42 so as to obtain the maximum second harmonic output,
The control for keeping the output of the second harmonic 19 constant (APC: Automatic Power Control) by the LD current control circuit 38 described above is omitted. When the output stabilization control is subsequently performed, the temperature of the MgO: LN crystal 42 may be set to the temperature at which the maximum second harmonic output is obtained.

In the present embodiment, in particular, in addition to obtaining the maximum second harmonic output as described above, the second temperature control circuit 39 sweeps the drive current of the Peltier element 45 to obtain MgO:
The temperature of the LN crystal 42 can be swept. At this time, the second temperature control circuit 39 receives a signal indicating the drive current value of the semiconductor laser 11 from the LD current control circuit 38, and
The temperature at which the semiconductor laser drive current is minimized with respect to the harmonic output is searched. After that, the second temperature control circuit 39
O: The drive current of the Peltier element 45 is controlled so that the temperature of the LN crystal 42 is maintained at the detected temperature.

Even in this case, the end face of the Nd: YAG crystal
The second harmonic 19, which is specularly reflected at 13a and turned back, and the second harmonic 19 superimposed thereon (the second harmonic 19 emitted directly to the side of the resonator mirror 14) are strengthened so as to maximize each other. The phases can be matched. The above configuration is
This is particularly preferable for securing long-term reliability of the solid-state laser device.

Instead of the above, the temperature of the MgO: LN crystal 42 at which the second harmonic output becomes maximum with respect to the constant optical output of the semiconductor laser 10 is searched, and the temperature of the MgO: LN crystal 42 is reduced. The same effect can be obtained by controlling the drive current of the Peltier element 45 so as to maintain the detected temperature.

In the embodiment described above, the MgO: LN crystal 42 is used as an optical component for phase adjustment. However, the present invention is not limited to this.
As long as the optical material is transparent to the second harmonic 19, any other glass or LiTaO ₃ can be applied. However, since this optical component changes the refractive index by changing the temperature, it is particularly desirable that the optical component be made of an optical material having a large temperature coefficient of the refractive index. In order to obtain a large phase change, it is desirable to use a longer optical component within a permissible range in consideration of other conditions.

Further, in this embodiment, the temperature of the MgO: LN crystal 42 is adjusted by the Peltier element 45, but a heater may be used instead. Further, here, the temperature of the MgO: LN crystal 42 is adjusted using the thermistor 44, but the MgO: LN crystal 42 is fixed to the resonator portion whose temperature is adjusted (that is, to the holding member 21). A constant amount of heat may be supplied to the MgO: LN crystal 42 so that a temperature difference is provided.

Next, a second embodiment of the present invention will be described with reference to FIGS. In these figures, the same elements as those in FIG. 1 are denoted by the same reference numerals, and redundant description thereof will be omitted (the same applies hereinafter).

FIG. 3 shows a side view of a semiconductor laser-excited solid-state laser device according to a second embodiment of the present invention. In the second embodiment, the phase control unit 40 provided in the apparatus of FIG.
O: A phase control unit 50 including an LN crystal 51 and the like is provided. In FIG. 3, components relating to temperature control of the resonator unit and APC driving of the semiconductor laser 11 are omitted (FIGS. 4 to 7).
The same).

Hereinafter, the phase control unit 50 will be described with reference to FIG. The MgO: LN crystal 51 has an inversion domain region 51a in which the same periodic domain inversion structure as the inversion domain LN crystal 16 of the first embodiment is formed.
A non-inversion region 51b is provided on the YAG crystal 13 side. The non-inversion region 51b is a region where the above-described periodic domain inversion structure is not formed.

The MgO: LN crystal 51 is fixed to the holding member 21 of the resonator via a quartz plate 52. Also Mg
O: A heater 53 that generates a certain amount of heat is mounted on the LN crystal 51.

In the second embodiment, when the heater 53 generates a certain amount of heat, a certain temperature difference is caused between the MgO: LN crystal 51 and the resonator, that is, between the MgO: LN crystal 51 and the holding member 21. I have to. Thus, MgO: LN
By setting the temperature of the crystal 51 to a desired value independently of the resonator section, the refractive index of the non-inversion region 51b of the MgO: LN crystal 51 can be controlled.

Therefore, the phase of the second harmonic 19 emitted from the inversion domain region 51a of the MgO: LN crystal 51 toward the Nd: YAG crystal 13 and turned back can be controlled. If so, the phase of the second harmonic 19 and the phase of the second harmonic 19 emitted directly to the resonator mirror 14 are matched, and they are superposed so as to reinforce each other, so that the maximum second harmonic output is obtained. Can be obtained.

Next, a third embodiment of the present invention will be described with reference to FIG. FIG. 5 shows a side view of a semiconductor laser-pumped solid-state laser device according to a third embodiment of the present invention. In the third embodiment, an Nd: YVO ₄ crystal 63 is used as a solid-state laser medium.
d: The YVO ₄ crystal 63 is excited by the laser beam 10 having a wavelength of 809 nm emitted from the semiconductor laser 11 and
Emit 1064nm light. The end face 63a of the Nd: YVO ₄ crystal 63 on the side of the inverted domain LN crystal 16 and the mirror face 14a of the resonator mirror 14 are provided with coatings for favorably reflecting light having a wavelength of 1064 nm.
Laser oscillation is caused between 14a, and a laser beam 18 as a fundamental wave having a wavelength of 1064 nm is obtained.

This laser beam 18 has an inverted domain LN
The crystal 16 converts the wavelength into a second harmonic 19 having a wavelength of す な わ ち, ie, 532 nm. Nd: end face 63a of YVO ₄ crystal 63
It is said that the coating formed in the step (1) well reflects the second harmonic 19 having a wavelength of 532 nm.

In this embodiment, Nd: YV
A phase control unit 60 is provided between the O ₄ crystal 63 and the Brewster plate 15. The phase control unit 60 includes a LiNbO ₃ crystal (hereinafter, referred to as an LN crystal) 61 having an electro-optic effect.
And a DC power supply 62 for applying a voltage to the LN crystal 61.

The LN crystal 61 is disposed on the optical path of the second harmonic 19 emitted from the inversion domain LN crystal 16 to the Nd: YVO ₄ crystal 63 side. When a voltage is applied to the LN crystal 61 from the DC power supply 62, the refractive index changes by an amount corresponding to the applied voltage value. Therefore, by controlling the voltage applied to the LN crystal 61, the refractive index of the LN crystal 61 is changed, and the phase of the second harmonic 19 passing therethrough can be controlled.

Therefore, the phase of the second harmonic 19 and the phase of the second harmonic 19 emitted directly to the side of the resonator mirror 14 are matched with each other.
They can be superimposed one on the other to obtain the maximum second harmonic output. In this example, the LN crystal
When the length of the 61 in the optical axis direction is 4 mm, the thickness is 0.4 mm, and the applied voltage is 100 V, the second
The phase relationship of the harmonics 19 could be adjusted to reinforce each other.

The crystal having the electro-optical effect is not limited to the above-mentioned LN crystal 61, but may be, for example, LiTaO ₃ , MgO.
Doped LiNbO ₃ or LiTaO ₃ , BaTi
Any other material such as O ₃ , ZnO, ADP, and KDP crystals can be used.

Next, a fourth embodiment of the present invention will be described with reference to FIG. FIG. 6 shows a side view of a semiconductor laser pumped solid-state laser device according to a fourth embodiment of the present invention. In the fourth embodiment, the phase control unit 7
0 is a quartz plate having a low thermal conductivity fixed to the holding member 21
Nd: YAG crystal 13 fixed on quartz plate 71
And a heater 72 similarly fixed on the quartz plate 71 at a position close to the Nd: YAG crystal 13.

In this configuration, when the heater 72 generates a certain amount of heat, a certain temperature difference occurs between the Nd: YAG crystal 13 and the holding member 21. Thus, the temperature of the Nd: YAG crystal 13 is set to a desired value independently of the resonator section,
The refractive index of the Nd: YAG crystal 13 can be controlled.

Therefore, it is possible to control the phase of the second harmonic 19 which is reflected and reflected at its end face 13a after passing through the Nd: YAG crystal 13. If so, this second harmonic 19
The phases of the second harmonics 19 emitted directly to the resonator mirror 14 are made to coincide with each other, and they are superposed so as to reinforce each other, so that the maximum second harmonic output can be obtained.

In this example, the length of N is 1 mm in the optical axis direction.
d: Using a YAG crystal 13 and N
d: By setting the temperature of the YAG crystal 13 to + 25 ° C., it was possible to adjust the two kinds of phase relations of the second harmonic 19 so as to reinforce each other. When the phase difference between these two second harmonics 19 is ± π / 2, the output of the second harmonic superimposed and output reaches about 70% of the maximum output. Therefore, if the phase difference can be set within a range of ± π / 2 without completely setting the phase difference to zero, the object of the present invention is sufficiently achieved.

If the temperature difference between the holding member 21 and the Nd: YAG crystal 13 is set too large, the adjustment of the resonator may be shifted due to the influence of thermal strain. It is desirable to set the temperature of crystal 13.

Next, a fifth embodiment of the present invention will be described with reference to FIG. FIG. 7 shows a side view of a semiconductor laser pumped solid-state laser device according to a fifth embodiment of the present invention. In the fifth embodiment, the phase control unit 80
Is composed of a heater 81 fixed to the holding member 20 of the excitation unit. In this case, the Nd: YAG crystal 13 is fixed to the holding member 20 of the excitation section. And the holding member 20
Is fixed on the base plate 30 via a glass plate 82 made of BK7 glass having a low thermal conductivity so that the temperature of the excitation unit can be set independently of that of the resonator unit.

In this configuration, the heater 81 generates a certain amount of heat, so that a certain temperature difference occurs between the Nd: YAG crystal 13 and the holding member 21 of the resonator. As an example, the glass plate 82 has a thickness of 0.25 mm, a size of 10 mm × 10 mm,
When the heater 81 generates a certain amount of heat within the range of 5 W, the temperature of the holding member 20 of the excitation unit can be maintained at a maximum of 50 ° C. with respect to the temperature of the holding member 21 of the resonator unit of 25 ° C. Thereby, when there is no temperature difference between the resonator section and the excitation section, regardless of the phase difference between the two kinds of second harmonics 19, they are superposed so as to reinforce each other. Thus, the maximum second harmonic output can be obtained.

As described above, Nd: YAG is used as the solid-state laser medium.
Although the embodiment using the crystal or the Nd: YVO ₄ crystal has been described, the solid-state laser medium in the present invention is not limited to the above, and may be, for example, an Nd: YLF crystal.

A mirror for regularly reflecting the wavelength-converted wave is also provided.
Not limited to those having a coating on the rear end face or the front end face of the solid-state laser medium, but also those having a coating on the rear end face or the front end face of other optical components such as generally known wave plates, and further, Alternatively, a mirror independent of those optical components and the solid-state laser medium can be applied.

[Brief description of the drawings]

FIG. 1 is a partially cutaway side view showing a semiconductor laser pumped solid-state laser device according to a first embodiment of the present invention.

FIG. 2 is a side view showing a main part of the solid-state laser device of FIG. 1;

FIG. 3 is a partially cutaway side view showing a semiconductor laser pumped solid-state laser device according to a second embodiment of the present invention;

FIG. 4 is a side view showing a main part of the solid-state laser device of FIG. 3;

FIG. 5 is a partially cutaway side view showing a semiconductor laser pumped solid-state laser device according to a third embodiment of the present invention.

FIG. 6 is a partially cutaway side view showing a semiconductor laser pumped solid-state laser device according to a fourth embodiment of the present invention.

FIG. 7 is a partially cutaway side view showing a semiconductor laser pumped solid-state laser device according to a fifth embodiment of the present invention.

FIG. 8 is an explanatory diagram for explaining a problem in a conventional solid-state laser device.

[Explanation of symbols]

10 Laser beam (excitation light) 11 Semiconductor laser 12 Condensing lens 13 Nd: YAG crystal 13a End face of Nd: YAG crystal 14 Resonator mirror 14a Mirror surface of resonator mirror 15 Brewster plate 16 Inverted domain LN crystal 17 Etalon 18 Solid Laser beam (fundamental wave) 19 Second harmonic 20, 21, 22 Holding member 25 Partial reflection mirror 26 Photodetector 30 Base plate 31 Peltier device 32 Package base 34 Package cap 36 Thermistor 37 First temperature control circuit 38 LD current control Circuit 39 Second temperature control circuit 40 Phase control unit 41 Quartz plate 42 MgO: LN crystal 43 Metal block 44 Thermistor 45 Peltier element 46 Heat sink 50 Phase control unit 51 MgO: LN crystal 51 a MgO: Inversion domain region of LN crystal 51 b MgO : Non-inverting region of LN crystal 52 Quartz plate 53 Heater 60 Phase controller 61 LN crystal 62 DC power 63 Nd: YVO ₄ crystal 70 phase controller 71 quartz plate 72 heater 80 phase controller 81 heater 82 glass plates

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 2H079 AA02 AA06 AA12 BA03 CA24 DA03 KA14 KA18 KA20 2K002 AB12 AB27 CA03 DA01 FA27 HA20 5F072 AB02 AB13 FF09 JJ04 JJ05 KK02 KK08 KK12 KK15 KK30 PP07 QQ02 SS01 TT01

Claims (6)

[Claims] 1. A solid-state laser medium, an excitation source for exciting the solid-state laser medium, a resonator, and an optical path of a laser beam as a fundamental wave reciprocating in the resonator, for wavelength conversion of the laser beam A solid-state laser device comprising: a nonlinear optical crystal that oscillates; and a mirror that regularly reflects a wavelength-converted wave emitted in one direction among two types of wavelength-converted waves emitted from the nonlinear optical crystal in directions opposite to each other. A solid-state laser device provided with means for controlling a refractive index of at least one optical component through which the wavelength-converted wave passes between the optical crystal and the mirror. 2. The solid-state laser device according to claim 1, wherein said means for controlling the refractive index comprises temperature control means for controlling the temperature of said optical component. 3. The solid-state laser device according to claim 2, wherein said temperature control means controls the temperature of said solid-state laser medium. 4. The nonlinear optical crystal has a region having a periodic domain inversion structure and a region having no periodic domain inversion structure, wherein the temperature control means controls the temperature of the nonlinear optical crystal. The solid-state laser device according to claim 2, wherein 5. The apparatus according to claim 1, wherein the optical component is a crystal having an electro-optic effect, and the means for controlling the refractive index applies a voltage to the crystal having the electro-optic effect. The solid-state laser device as described in the above. 6. A phase difference between a wavelength-converted wave emitted from the nonlinear optical crystal in a direction opposite to the one direction and the specularly reflected wavelength-converted wave superimposed on the wavelength-converted wave is ± π. The solid-state laser device according to any one of claims 1 to 5, wherein the ratio is within / 2.