JPH0669567A - Semiconductor laser-excited solid laser equipment - Google Patents

Abstract

PURPOSE:To restrain output fluctuation and obtain stable output, by arranging one surface of a metal block and the facing surface of Nd:YVO crystal so as to be in contact with each other, and thermally coupling them. CONSTITUTION:A semiconductor laser chip 11 is bonded to the heat absorbing plate of a thermoelectric cooling element 13 via a copper made metal block 12 by using thermally conducting adhesive agent. The metal block 12 is fixed to an optical cabinet 16 so as to be in surface-contact with Nd:YVO4 crystal 14 by using screws. The semiconductor laser pumping light incidence surface where the temperature rises most in the Nd:YVO4 crystal 14 by absorbing semiconductor laser pumping light is in contact with the surface of the metal block 12 whose surface temperature is controlled to be constant by the thermoelectric cooling element 13. Hence the temperature of the semiconductor laser pumping light incidence surface of the Nd:YVO4 crystal 14 becomes equal to the temperature of the metal block 12, and is always controlled to be constant by the thermoelectric cooling element 13, so that the output fluctuation of a solid laser equipment is restrained and stable output can be obtained.

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 semiconductor laser pumped solid-state laser device in which the output fluctuation of solid-state laser light is reduced.

[0002]

2. Description of the Related Art A semiconductor laser pumped solid-state laser device (hereinafter referred to as a solid-state laser device) excites a solid-state laser medium by a semiconductor laser beam to cause laser oscillation, and is small in size, light in weight, long in life, and electro-optical. It has features such as high conversion efficiency and stable operation, and its use is expanding in various industrial fields. In recent years, many attempts have been made to realize green lasers and blue lasers in the visible range by combining a nonlinear optical element and a solid-state laser.

FIG. 5 shows a cross section of a solid-state laser device. The solid-state laser medium 43 is Nd: YAG (neodymium: yttrium aluminum oxide), Nd: YVO.
₄ , Nd: YLF (neodymium: yttrium lithium fluoride) or the like is used. As the semiconductor laser 41, one having an output of 100 mW or more at an oscillation wavelength of 808 to 810 nm which is an absorption wavelength range of the solid laser medium 43 is used.

The semiconductor laser light incident surface of the solid-state laser medium 43 and the concave surface of the output mirror 44 are the fundamental wave 1 of the solid-state laser.
A coating having a high reflectance for 053 to 1064 nm is formed to form a solid-state laser resonator (hereinafter referred to as a resonator). When the semiconductor laser light is condensed on the solid-state laser medium 43 by the condensing optical system 42, solid-state laser oscillation occurs in the resonator, and a part thereof is emitted to the outside through the output mirror 44. When the nonlinear optical element is inserted in this resonator, the second harmonic or the third harmonic of the solid-state laser fundamental wave is generated by the interaction between the nonlinear optical element and the solid-state laser fundamental wave. The second harmonic, that is, the solid-state laser fundamental wave
Attempts to realize a laser with a wavelength of / 2 are active.

In such a solid-state laser device, when an Nd: YVO ₄ crystal is used as the solid-state laser medium 43, N
d: YVO4 crystal is the oscillation wavelength of semiconductor laser
The absorption coefficient in the region of 8 to 810 nm is about 4 times that of the Nd: YAG crystal, and the thermal conductivity is about 1 of that of the Nd: YAG crystal.
Therefore, the temperature of the semiconductor laser excitation light absorption portion of the Nd: YVO ₄ crystal rises and the output of the solid-state laser light fluctuates.

For example, the semiconductor laser excitation light power is 50
At 0 mW and excitation light spot size of 100 μm, N
It is known that the temperature of the central portion of the excitation light spot on the semiconductor laser excitation light incident surface of the d: YVO4 crystal rises by about 40 ° C., and the output of the solid-state laser light decreases to 1/3 accordingly. (The Institute of Electronics, Information and Communication Engineers Technical Group OQE91-
30P73-78)

3 mm × 3 mm × 1 mm Nd: YVO4
The crystal was embedded in an aluminum holder of 10 mm x 10 mm x 2 mm and fixed with an adhesive, and the semiconductor laser oscillation wavelength was 809 nm and the semiconductor laser excitation light power was 200 m.
W, Nd: Y under the condition of excitation light spot size 100 μm
As a result of measuring the temperature fluctuation of the aluminum holder and the output change of the solid-state laser light when the VO ₄ crystal was excited, the output fluctuation of the solid-state laser light was ± 15%, which was roughly synchronized with the temperature fluctuation of the aluminum holder. I found out that
It is considered that this is a cycle in which the semiconductor laser excitation light absorption of Nd: YVO ₄ crystal-temperature increase-solid-state laser output decrease-temperature decrease-semiconductor laser excitation light absorption increase-temperature increase is repeated.

[0008]

SUMMARY OF THE INVENTION An object of the present invention is to suppress the output fluctuation of a solid-state laser device in which the solid-state laser medium is Nd: YVO ₄ and obtain a solid-state laser device having a stable output. .

[0009]

According to the present invention, there is provided a semiconductor laser chip, a metal block supporting the semiconductor laser chip, an electronic cooling element bonded to the metal block, and a heat sink having the electronic cooling element fixed thereto. Nd: Y arranged to face the laser excitation light emitting surface of the semiconductor laser chip
A solid-state laser medium of VO ₄ crystal, an output mirror arranged in front of the laser excitation light emitting surface of the Nd: YVO ₄ crystal, an optical housing to which the output mirror is fixed, the metal block in the optical housing, In a semiconductor laser pumped solid-state laser device in which a solid-state laser medium and the heat sink are fixed, one surface of the metal block and the facing surface of the Nd: YVO4 crystal are arranged in contact with each other, and the facing surface is thermally coupled. It is a feature.

[0010]

According to the present invention, the semiconductor laser excitation light incident surface, which has the highest temperature in the Nd: YVO ₄ crystal due to absorption of the semiconductor laser excitation light, has a metal block whose temperature is controlled to a constant temperature by the electronic cooling element. Is in contact with the surface of. Therefore, the temperature of the semiconductor laser excitation light incident surface of the Nd: YVO4 crystal becomes equal to the temperature of the metal block, and is constantly controlled to a constant temperature by the electronic cooling element.

Therefore, it is possible to suppress the output fluctuation of the solid-state laser device due to the temperature change of the Nd: YVO ₄ crystal and obtain the solid-state laser device of stable output. Furthermore, N
The surface of the d: YVO ₄ crystal which is the semiconductor laser excitation light incident surface excluding the semiconductor laser excitation light incident portion is Au,
When coated with at least one metal or alloy selected from Ag, Cu, and Al, the metal is rich in ductility, so N
The contact property between the semiconductor laser excitation light incident surface of the d: YVO ₄ crystal and the metal block is improved, and the above-mentioned action can be made more reliable.

[0012]

1 is a sectional view showing an embodiment of a solid-state laser device according to the present invention. A semiconductor laser chip 11, a metal block 12, an electronic cooling element 13, an Nd: YVO ₄ crystal 1 are shown.
4, output mirror 15, optical housing 16, heat sink 1
7, a radiation fin 18, and a heat insulating member 19. As the semiconductor laser chip 11, a multimode oscillation semiconductor laser having a wavelength of 809 nm and an output maximum of 500 mW was used.

The semiconductor laser chip 11 is provided with a thermoelectrically conductive adhesive 13 via a copper metal block 12 and a thermally conductive adhesive.
Bonded to the endothermic plate of the metal block 12 with N
d: Optical housing 16 so as to make surface contact with the YVO4 crystal 14
Fixed to. Nd: YVO ₄ crystal 14 is 3 × 3 × 1 m
With a size of m, the semiconductor laser excitation light incident surface has a wavelength of 80
A coating was applied so as to be non-reflective at 9 nm and highly reflective at a wavelength of 1064 nm to form a resonator between the concave surface of the output mirror 15.

The output mirror 15 has a diameter of 15 × 5 mm and a radius of curvature of 50 mm. Each optical element of the Nd: YVO ₄ crystal 14 and the output mirror 15 was fixed to the optical housing 16 made of aluminum by using screws while adjusting the positions thereof precisely. The heat sink 17 with the heat radiating fins 18 has a central portion joined to the heat radiating plate of the electronic cooling element 13 by a heat conductive adhesive, and a peripheral portion made of an acrylic resin plastic through a tetrafluoroethylene resin (heat insulating member 19). Optical housing with screws 1
It was fixed at 6.

The dotted line 31 in FIG. 2 shows the time change of the output of the solid-state laser device of this embodiment, and the output fluctuation was within ± 5%. In the figure, the solid line 32 indicates the metal block 12 and N.
The time variation of the output of the conventional solid-state laser device using the same optical system and optical element as the present embodiment except that the d: YVO ₄ crystal 14 is not in contact is shown, and the output fluctuation is ± 15%. .

In the solid-state laser device of this embodiment, the semiconductor laser excitation light incident surface is in contact with the surface of the metal block 12 whose temperature is controlled at a constant temperature by the electronic cooling element 13, so that Nd: YVO ₄ The temperature of the semiconductor laser excitation light incident surface of the crystal 14 becomes equal to the temperature of the metal block 12, and is constantly controlled to a constant temperature by the electronic cooling element 13, and the time change of the output of the solid-state laser device is 3 times as compared with the conventional example. You can see that it is suppressed to one-half.

FIG. 3 is an enlarged view of a main part of another embodiment of the present invention, which is a semiconductor laser chip 11 and a metal block 1.
2, the electronic cooling element 13 and the Nd: YVO ₄ crystal 14 are shown. A solid-state laser in which a gold thin film 20 is deposited to a thickness of 3 μm on the surface of the Nd: YVO ₄ crystal 14 on which the semiconductor laser excitation light is incident, excluding the semiconductor laser excitation light incident portion, by a known sputtering method. It is an example of an apparatus.

A gold thin film 20 having a thickness of 3 μm is formed on the surface of the Nd: YVO ₄ crystal 14 on which the semiconductor laser excitation light is incident by the well-known technique, excluding the semiconductor laser excitation light incident portion. I wore it. The gold thin film at the center of the semiconductor laser excitation light incident surface of the Nd: YVO ₄ crystal 14 having the gold thin film 20 deposited thereon was removed into a circular shape having a diameter of 200 μm by the known etching method. The area of the gold thin film 20 to be removed is equal to or larger than the beam diameter of the incident semiconductor laser and is preferably as small as possible. The stripe width of the active layer of the semiconductor laser used in this embodiment is 100 μm, and the beam diameter of the solid-state laser fundamental wave emitted is determined by the radius of curvature of the concave surface of the output mirror 15 and the cavity length. Since the radius of curvature is 50 mm and the resonator length is 7 mm, it is 77 μm.

Therefore, in this embodiment, the diameter of the gold thin film 20 to be removed is set to 200 μm in consideration of the margin for adjusting the position of the optical element. The solid line 33 in FIG. 2 shows the change over time in the output of the solid-state laser device of this embodiment, and the output fluctuation was within ± 3%. The semiconductor laser excitation light incident surface is in contact with the surface of the metal block 12 controlled to a constant temperature by the electronic cooling element 13, and Nd: YVO
4 The gold thin film 20 was deposited to a thickness of 3 μm on the surface of the crystal 14 on which the semiconductor laser excitation light was incident, excluding the semiconductor laser excitation light incident portion, by the known sputtering method. The contact with the surface is improved and N
The temperature of the semiconductor laser excitation light incident surface of the d: YVO ₄ crystal 14 is more surely controlled to a constant temperature by the electronic cooling element, and the time change of the output of the solid-state laser device is reduced to 1/5 as compared with the conventional example. You can see that it is suppressed.

In the above embodiment, Nd: YVO
_Although an example in which gold is used as a metal for coating the semiconductor laser excitation light incident surface of the ₄ crystal 14 has been shown, the present invention is not limited to this, and a good thermally conductive metal such as copper, silver, and aluminum that is rich in ductility. Can be used.

In the embodiments described above, the optical system for oscillating the fundamental wave of the solid-state laser is shown. However, the present invention is not limited to this, and KTiOPO ₄ (titanium phosphate) is used in the solid-state laser resonator. A non-linear optical element such as potassium) is inserted, and the second harmonic of the solid-state laser fundamental wave, that is, a laser having a half wavelength of the solid-state laser fundamental wave is realized by the interaction between the non-linear optical element and the solid-state laser fundamental wave. You can Since the output of the second harmonic is proportional to the square of the power of the fundamental wave in the resonator, the output variation of the second harmonic has a magnitude obtained by amplifying the output variation of the solid-state laser fundamental wave. Therefore, the present invention capable of stabilizing the output of the fundamental wave of the solid-state laser is particularly effective for the second harmonic generation solid-state laser device.

FIG. 4 is a sectional view of a solid-state laser device according to another embodiment of the present invention. The solid-state laser oscillates a second harmonic of the solid-state laser fundamental wave, that is, a laser having a half wavelength of the solid-state laser fundamental wave. 2 shows a cross section of the device. In the solid-state laser device of this embodiment, KTiOPO ₄ is used as the nonlinear optical element.
Crystal 21 was used. KTiOPO ₄ crystal 21 is 3 × 3
In the size of × 5 mm, the incident surface of the solid-state laser fundamental wave was polished to a flat surface and coated so as to be non-reflective with respect to the solid-state laser fundamental wave (λ = 1064 nm) and the second harmonic (λ = 532 nm). .

On the other hand, the emission surface of the solid-state laser fundamental wave is R = 5.
Spherical polishing to a 0 mm convex surface, solid-state laser fundamental wave (λ = 1
(064 nm) was coated to have high reflection, and the second harmonic (λ = 532 nm) was coated to be non-reflection. By doing so, the solid-state laser resonator is composed of the semiconductor laser excitation light incident surface of the Nd: YVO ₄ crystal 14 and the spherical surface of the KTiOPO ₄ crystal 21, so that the output mirror can be omitted and the solid-state laser fundamental wave Second harmonic, that is, 1/2 of fundamental wave of solid-state laser
It is possible to reduce the size of a solid-state laser device that oscillates a laser of the wavelength.

The output fluctuation of the solid-state laser device of this embodiment is ±
Within 6%, the output fluctuation of the solid-state laser device of the conventional example using the same optical system and optical element as that of the present embodiment, except that the metal block 12 and the Nd: YVO ₄ crystal 14 are not in contact, is ± 27. %Met. It is apparent that the present invention is particularly effective for the second harmonic generation solid state laser device.

[0025]

As described above, according to the present invention, the output fluctuation of the solid-state laser device in which the solid-state laser medium is Nd: YVO ₄ can be suppressed, and the solid-state laser device having a stable output can be obtained.

[Brief description of drawings]

FIG. 1 is a sectional view showing an embodiment of a solid-state laser device according to the present invention.

FIG. 2 is a characteristic diagram showing a time variation of an output of a solid-state laser device.

FIG. 3 is an enlarged view of a main part in another embodiment of the present invention.

FIG. 4 is a sectional view of a solid-state laser device according to another embodiment of the present invention.

FIG. 5 is a sectional view of a conventional solid-state laser device.

[Explanation of symbols]

11 Semiconductor Laser Chip 12 Metal Block 13 Electronic Cooling Element 14 Nd: YVO ₄ Crystal 15,44 Output Mirror 16 Optical Housing 17 Heat Sink 18 Radiating Fin 19 Heat Insulating Member 20 Gold Thin Film 21 KTiOPO ₄ Crystal 41 Semiconductor Laser 42 Focusing Optical System 43 Solid-state laser medium 45 holder

Claims (2)

[Claims] 1. A semiconductor laser chip and the semiconductor laser
Contact the metal block that supports the chip and the metal block.
Combined thermoelectric cooler and heater with the thermoelectric cooler fixed
Tosink and laser excitation light output of the semiconductor laser chip
Nd: YVO placed facing the projection surface _Four Crystal solid laser medium
Quality and the Nd: YVO_Four Front side of laser excitation light emission surface of crystal
The output mirror arranged in the
A housing, and the metal block and the solid-state laser on the optical housing.
The medium and a semiconductor laser having the heat sink fixed
In a pumped solid-state laser device, one surface of the metal block
And the above Nd: YVO_Four Place the facing surface of the crystal in contact,
A semiconductor laser characterized in that the facing surfaces are thermally coupled.
Laser pumped solid state laser device. 2. A semiconductor laser excitation light incident surface of the Nd: YVO ₄ crystal, the surface excluding the incident portion of the semiconductor laser excitation light being at least one selected from Au, Ag, Cu and Al. 2. A semiconductor laser pumped solid-state laser device according to claim 1, which is coated with a metal or an alloy.