JP2576415B2 - Laser diode pumped solid state laser - Google Patents

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 using a semiconductor laser as a pumping light source, and more particularly to a compact laser diode-pumped solid-state laser having a nonlinear optical crystal disposed in a laser resonator (hereinafter referred to as an LD-pumped solid-state laser). About.

[0002]

2. Description of the Related Art A conventional solid-state laser using a semiconductor laser as an excitation light source is disclosed in U.S. Pat. No. 4,942,582 issued on Jul. 17, 1990.
There is disclosed a basic configuration in which a laser resonator is formed by a laser medium having a reflection film formed on one surface and an output mirror, and light emitted from a semiconductor laser is projected onto a laser medium of the laser resonator via a lens. In this basic configuration in which the laser medium is excited by the semiconductor laser light and the excitation wavelength of the laser medium is amplified by the laser resonator and emitted from the output mirror, a nonlinear optical crystal such as KTP is further provided between the laser medium and the output mirror. A configuration in which the second harmonics are arranged to generate the second harmonic has also been proposed.

[0003]

However, the configuration disclosed here is only a basic concept, and there is no teaching about a specific holding means of each component. In particular, the laser medium and the nonlinear optical crystal have a problem that the laser oscillation efficiency is reduced due to a rise in temperature. In addition, since the organic nonlinear optical crystal has deliquescence, there is a problem that when it is used in the atmosphere, the change with the passage of time is extremely short and the life is short.

[0004]

SUMMARY OF THE INVENTION An object of the present invention is to provide an LD having a compact structure capable of suppressing deterioration of laser oscillation efficiency due to a rise in temperature and achieving a longer life of a nonlinear optical crystal.
An object of the present invention is to provide a pumped solid-state laser.

According to the present invention, there is provided a hollow member for hermetically integrating a laser resonator having a built-in nonlinear optical crystal, and a thin portion is provided at the center of the hollow member and the thin portion is evacuated to thereby reduce the thin portion. The laser medium, the nonlinear optical crystal, and the output mirror are closely arranged and deformed to be compact, and can be further integrated with the semiconductor laser light source.

[0006]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to FIG. 1, a hollow member 7 has a thin portion 71 substantially at its center. The thin portion 71 is obtained by forming a groove so as to go around the outer surface of the side wall of the hollow member 7. The laser medium 3 on which the reflection film 31 is formed is inserted into one opening of the hollow member 7 and hermetically sealed with an adhesive 8. The nonlinear optical crystal 4 is placed inside the hollow member 7, the output mirror 5 having the reflection film 51 formed in the other opening of the hollow member 7 is inserted, and hermetically sealed with an adhesive 8. An exhaust pipe 9 is provided near the groove of the hollow member 7. When the inside of the hollow member 7 is evacuated through the exhaust pipe 9, the thin portion 71 undergoes compressive deformation such that both end faces of the nonlinear optical crystal 4 are tightly fixed between the laser medium 3 and the output mirror 5. . If the exhaust pipe 9 is pressed and airtightly sealed after the evacuation is completed, an airtight laser resonator unit 70 in which the laser medium 3 and the hollow member 7 are integrated and integrated is obtained as shown in FIG. A laser diode unit 10 as a light source for exciting the laser resonator 70 is arranged on the side of the laser medium 3 and connected and fixed by a connecting member 17. The laser diode unit 10 includes a base substrate 101
And a cap 103 having a transparent window 102 constitute an airtight package, and a laser diode 105 is mounted on a built-in heat sink 104. The laser diode 105 emits output light by a driving voltage applied via the bonding wire 106 and the external terminals 107 and 108. The output light of the laser diode enters the laser medium 3 and is absorbed and converted into a fundamental wave. Then, the laser light is amplified by the laser resonator 70 and the second
The light is emitted from the output mirror 5 as the output light of the second harmonic.

The reflection film 31 of the laser medium 3 has a high transmittance for the light emitted from the laser diode, and has a high reflection for the light excited by the laser medium 3 and the second harmonic obtained by the nonlinear optical crystal 4. And is formed on one side of the laser medium 3 by a method well known to those skilled in the art. As is well known, the reflection film 51 of the output mirror 5 has a high reflectance of 99.8% or more with respect to the fundamental wave and a high transmittance of 80% or more with respect to the second harmonic, and has a laser resonator. The unit 70 is formed so that output light of the second harmonic can be obtained.

[0008] The LD-pumped solid-state laser thus constructed is composed of a laser diode unit 10 and a laser medium 3.
Are disposed close to each other, so that not only a condensing lens is unnecessary, but also because the laser medium 3, the nonlinear optical crystal 4, and the output mirror 5 are in close contact with each other, the resonator length is 5 mm.
Since the alignment adjustment of the optical components is not required, the size can be reduced.

The material of the hollow member 7 is preferably a material having a high thermal conductivity in order to efficiently radiate heat generated in the laser medium 3 and a material whose thin portion 71 is deformable. In this respect, metals such as copper and aluminum are preferable. In the case of the copper hollow member 7, the thickness of the thin portion 71 is preferably selected in the range of 0.1 mm to 0.2 mm.
An epoxy resin such as Tall Seal (trademark of Varian) is used as the adhesive 8. In addition, it is preferable that a step as shown in the drawing is formed on the inner wall surface of the hollow member 7 in the openings at both ends of the hollow member 7 so that the laser medium 3 and the output mirror 5 can be easily inserted and fixed. In the illustrated example, a step is formed by making the inner diameter of the inside of the hollow member 7 smaller than the inner diameter of both ends. The length of the central portion having a small inner diameter in the tube axis direction is slightly longer than the dimension of the nonlinear optical crystal 4 in the optical axis direction, and the dimension of the nonlinear optical crystal 4 in the optical axis direction due to deformation of the thin portion 71 due to evacuation. It is designed to be the same as The order of assembling is not particularly limited, but if the nonlinear optical crystal 4 is temporarily fixed in advance to one of the laser medium 3 and the output mirror 5 and incorporated, the assembling process is further simplified. The position of the exhaust pipe 9 is such that the through hole is the hollow member 7.
Any location may be used as long as it is conductive to a region having a small inner diameter. It is desirable that the shape of the opening of the hollow member 7 accommodating the laser medium 3 be the same as the outer shape of the laser medium 3 in order to enhance the heat radiation effect.

Although the groove of the hollow member 7 is formed on the outer wall surface in the illustrated example, it is needless to say that the groove may be formed on the inner wall surface side. It is desirable that the laser light emitting surface of the laser diode unit 10 and the reflection film 31 of the laser medium 3 be close to each other in terms of coupling efficiency. Alternatively, a structure in which the inside of the hollow member 7 is evacuated and then filled with an inert gas in an airtight container and hermetically sealed may be used. Further, a cooling fin may be attached to the outer surface of the hollow member 7 or the connecting member 17 to further improve the cooling efficiency.

The operation of the present invention when the laser laser of the laser diode unit 10 is of the GaAs / GaAlAs type will be described below. The laser light having a wavelength of 810 nm emitted from the laser diode unit 10 enters from the reflection film 31 side of the laser medium 3. When the laser medium 3 is Nd: YVO4, the laser medium 3 absorbs the laser light and is optically excited to generate light having a wavelength of 1.06 μm. This light is reflected by the reflection film 31 of the laser medium 3 and the output mirror 5.
The light is amplified within the laser resonator composed of the reflection film 51 of FIG. Since the nonlinear optical crystal 4 such as PCNB or DAN is installed in the laser resonator, the wavelength is 1.06 μm.
Is converted into a second harmonic by the nonlinear optical crystal 4, and visible light having a wavelength of 532 nm is emitted from the outside of the output mirror 5. The reflection film 31 of the laser medium 3 has a wavelength of 8
It has a high transmittance (90%) for a laser beam of 10 nm, and the reflective film 51 of the output mirror 5 has a transmittance of 0.2% or less for light having a wavelength of 1.06 μm. Laser medium 3
And an example of specific dimensions of the output mirror 5 is 4 m
It has a square entrance surface and an exit surface of mx 4 mm, and has a length in the optical axis direction, that is, a thickness of 1 mm. An example of specific dimensions of the nonlinear optical crystal 4 is a square 3 mm × 3 mm incident surface and an exit surface, and the length in the optical axis direction is 5 mm.
mm. Emission surface of semiconductor laser device and laser medium 3
Is preferably 3 mm or less so as not to lower the optical coupling efficiency.

[0012]

As described above, according to the present invention, the nonlinear optical crystal 4 is sealed in a vacuum-tight manner and the laser medium 3 and the nonlinear optical crystal 4 are integrated by the hollow member 7 having good heat conduction characteristics. Is dissipated through the hollow member 7, and the heat generated by the nonlinear optical crystal 4 is also dissipated through the hollow member 7 through the laser medium 3, so that a decrease in laser oscillation efficiency can be suppressed. Further, since the nonlinear optical crystal 4 is isolated from the atmosphere, a long life is guaranteed, and a practical LD capable of obtaining a compact and easy-to-handle laser resonator 70 is obtained.
Pumped solid-state lasers can be achieved.

[Brief description of the drawings]

FIG. 1 is a sectional view showing a first embodiment of the present invention.

FIG. 2 is a perspective view of the hollow member 7 of FIG.

[Explanation of symbols]

 Reference Signs List 3 laser medium 4 nonlinear optical crystal 5 output mirror 7 hollow member 8 adhesive 9 exhaust pipe 10 laser diode unit 17 connecting member 31 reflective film 51 reflective film 70 hermetic laser resonator unit 71 thin portion 105 laser diode

Claims (10)

(57) [Claims] An output mirror that hermetically seals one end of a hollow member; a laser medium that hermetically seals the other end of the hollow member to form an optical resonator with the output mirror; and a center of the hollow member. Having a nonlinear optical crystal disposed so as to be in close contact with both the output mirror and the laser medium by deforming a portion, and a semiconductor laser light source disposed on the opposite side of the laser medium from the nonlinear optical crystal. A solid-state laser pumped by a laser diode. 2. An exhaust pipe is provided in the hollow member, and the inside of the hollow member is exhausted through the exhaust pipe to reduce the pressure in the hollow member. Laser diode pumped solid state laser. 3. The laser-diode-pumped solid-state laser according to claim 1, wherein a thin portion is formed on a part of a side wall of the hollow member, and the thin portion is compressed and deformed by the reduced pressure. 4. The laser diode-pumped solid-state laser according to claim 1, wherein the hollow member is filled with an inert gas. 5. The laser-diode-pumped solid-state laser according to claim 3, wherein said thin portion is obtained by forming a groove in an outer wall of said hollow member. 6. The laser-diode-pumped solid-state laser according to claim 1, wherein said hollow member is formed of a metal having good thermal conductivity. 7. The laser-diode-pumped solid-state laser according to claim 1, wherein said hollow member and said and said output mirror are connected by an adhesive. 8. The laser according to claim 1, wherein a reflection coat is formed on a surface of said output mirror in contact with said nonlinear optical crystal and on a surface of said laser medium on a side opposite to said nonlinear optical crystal. Diode-pumped solid-state laser. 9. The laser-diode-pumped solid-state laser according to claim 1, wherein said semiconductor laser light source and said hollow member are integrated via a connecting member. 10. An optical resonator having an airtight structure is constituted by an output mirror hermetically sealed at one end of a hollow member with an adhesive, and a laser medium airtightly sealed at the other end of the hollow member with an adhesive. The nonlinear optical crystal disposed between the output mirror and the laser medium depressurizes the inside of the optical resonator, so that the nonlinear optical crystal, the output mirror, and the laser medium are in close contact with each other. The thin portion provided on the side wall of the member is deformed, and the semiconductor laser light source disposed on the opposite side of the laser medium from the nonlinear optical crystal and the hollow member are integrated via a connecting member. A solid-state laser pumped by a laser diode.