JPH03145776A - Slab type laser medium - Google Patents

Abstract

PURPOSE:To enable a laser medium to be brought into direct contact with water to cool by a method wherein a thin plate as a protective member is formed of glass material more excellent than laser glass which forms a laser medium base in water resistance, and the protective member concerned is fixed to the outer faces of the two opposed sides of the laser medium base respectively in one piece. CONSTITUTION:A laser medium base 11 is formed of laser glass composed of phosphate glass such as fluorophosphate glass or silica phosphate glass which is doped with 8.7% by weight of Nd ion as a laser active mateiral. Protective members 12 and 13 are formed of silicate glass such as borosilicate glass or the like, and the faces 12a and 13 of them are fusion-welded by heating to the faces 11a and 11b of the laser medium base 11 opposed to each other in a thicknesswise direction respectively. The protective members 12 and 13 are very excellent in water resistance as compared with phosphate glass.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a slab-type laser medium that can be cooled by bringing water into direct contact with the laser medium.

[Prior Art] A slab-type laser medium is known as a laser medium that can stably oscillate a relatively high-power laser beam.

This slab-type laser medium allows laser oscillation to occur by causing laser resonant light traveling through a relatively thin plate-shaped laser medium to travel in a zigzag pattern by alternately reflecting it on two opposing surfaces. This is what I decided to do.

This slab-type laser medium can cool the thin plate-like laser medium from both sides, ensuring good cooling efficiency.At the same time, the laser resonant light travels in a zigzag pattern within the laser medium, so A long effective excitation optical path length can be obtained. Therefore, relatively high-power laser light can be stably oscillated.

By the way, as a method for cooling this slab type laser medium, it is considered most desirable from the viewpoint of cooling efficiency and ease of handling to apply a method of cooling the laser medium by bringing water into direct contact with the laser medium.

However, fluorinate, which is most suitable for constructing this slab-type laser medium, or laser glass containing phosphate as a main component does not have resistance to water.

On the other hand, silicate glass, known as a laser glass that is resistant to water, has a nonlinear coefficient of 1.53X.
10"' e su (for phosphate glass, 1.1 to 1.2 Stimulated emission cross section is 2
．． Since it is as small as 7 x 10" cm (for phosphate glass, it is 4.1 to 4.2 x 10" cm), it cannot be used as a slab type laser medium due to reasons such as low oscillation efficiency.

Therefore, conventionally, a slab type laser medium has been constructed of fluorinate or a laser glass containing phosphate as a main component, and has been cooled by the following cooling method that does not cause damage due to water.

■ Method of cooling the laser medium by bringing the following cooling liquid into direct contact with the laser medium (by KOeClllner, Sp.
r: nger-VerlAq Publishing rSol
id 5tate l-aserEngineeri
ng J) a. A mixed solution of water (50%) and ethylene glycol (50%). Fluorocarbon liquid C1 A mixed solution of water (60%) and methanol (40%) ■ Contact with the cooling liquid of the laser medium. A method of coating the surface with MgF2 or fluoropolymer to form a protective film and cooling it with water.

■ A so-called conduction cooling method, in which a cooling plate is placed opposite the cooling surface of the laser medium with a predetermined gap, and He gas with high thermal conductivity is passed through the gap. In this case, as the cooling plate, for example, a water-cooled sapphire plate is used; E, (IEEE J, Q,
E Vol QE-21, No! + PdI2~414
reference).

[Problems to be Solved by the Invention] However, each of the above-mentioned conventional methods has the following problems.

Each coolant used in this method contains C-H or F-H bonds, and these bonds absorb excitation light and deteriorate the coolant, so the durability of the coolant is limited. short.

In this method, there is a high risk that the coated protective film will swell or peel off due to the action of water during use, and the durability is not sufficient. In particular, when the protective film is made of an organic film, the coefficient of thermal expansion is about one order of magnitude higher than that of glass, so fatigue is likely to occur due to the difference in thermal expansion, and the protective film is also susceptible to optical damage due to the action of excitation light.

This method has a lower cooling effect than methods such as water cooling or bringing a solution into contact with the laser medium.

The present invention was made against the above-mentioned background, and an object of the present invention is to provide a slab-type laser medium that has a relatively simple configuration and can be cooled by bringing water into direct contact with the laser medium. It is something.

[Means for Solving the Problems] The present invention solves the above problems by having the following configuration.

A slab-type laser medium that performs laser oscillation by alternately reflecting laser resonant light traveling in a plate-shaped laser medium on two opposing surfaces and causing it to travel in a zigzag pattern, a laser medium base formed in a plate shape of laser glass; and a thin plate formed of a glass material with higher resistance to water than the laser glass constituting the laser medium base, the laser medium base facing each other; A protection member is integrally formed with the laser medium base by fixing one surface of each of the two surfaces to the outer surface of the two surfaces.

[Function] In the above configuration, the surfaces of each of the protection members that contact the outside are surfaces that face each other, and the laser resonant light is alternately reflected from these surfaces and travels in a zigzag pattern within the laser medium. By doing so, laser oscillation can be performed.

In this case, even if water is brought into direct contact with the outer surface of the protection member for cooling, the laser medium will not be eroded by water.

"Example" Fig. 1 is a perspective view of a slab type laser medium according to an embodiment of the present invention, Fig. 2 is a sectional view taken along the line ■-■ of Fig. 1, and Fig. 3 is a usage example of the embodiment. It is an explanatory diagram.

Hereinafter, one embodiment will be described in detail with reference to these drawings.

In the figure, reference numeral 10 indicates a slab type laser medium, and reference numeral 11
12 and 13 are protection members, 21 and 22 are excitation light sources, and 31 and 32 are resonant mirrors.

The slab type laser medium 10 is a substantially belt-shaped plate having a thickness of about 10 mm, a length of 100 mm, and a width of about several tens of mm.

The two opposing surfaces in the thickness direction of this slab type laser medium 10 are formed to be extremely accurately parallel (plane parallelism: 10 seconds), and the reflecting surface 10a of the laser resonant light is
, ], constitutes Ob.

In addition, the two surfaces facing each other in the length direction of this slab type laser medium 10 are also formed to be exactly parallel (surface parallelism: 23 seconds), and the laser resonant light input/output surface 10 is
c, constitute 10d. In this case, these people/emission surface 1
The angle α formed by 0c and 10d with respect to the reflecting surfaces 1.0a and 10b is selected so as to accurately form a predetermined angle. That is, angles are selected such that the resonant light that enters and exits the slab-type laser medium 10 through the input/output surfaces 10c and 1-Od enters and exits at the B-edge Euster angle. . In this example, α146.92°
is set to

Note that these reflective surfaces 10a, 10b and the entrance/exit surface 10
C and 10d are subjected to precision polishing, and the area degree is maintained at approximately λ/2.

On the other hand, the two surfaces (side surfaces>10d and 10f) facing each other in the width direction of this slab type laser medium 10 do not require high accuracy in both parallelism and surface area. The surface may have a roughness of about 10 μm as measured by a surface roughness measuring device called Kristetub.

The slab type laser medium 1-0 includes a laser medium base 11 having a similar shape to the external shape of the slab type laser medium 1.0, and two surfaces 11a and 11a facing each other in the thickness direction of the laser medium base 11. It is integrally formed with protective members 12 and 13 fixed to 11-b, respectively.

The laser medium base 11 has a thickness of 10 mm and a length of 150 mm.
It is a substantially strip-shaped plate with a width of about 30 mm.

The laser medium base 1 is made of a laser glass in which 8.7 wt % of Nd ions are doped as a laser active substance into a phosphate glass such as fluorophosphate glass or silica phosphate glass. In this example, the refractive index of the laser medium base 1 is 1.53510 for light with a wavelength of 1.06 μrn, and the thermal expansion coefficient is 103
．． 2 x 10'/°C.

The protective members ]-2 and 1-3 are made of silicate glass such as borosilicate glass, and have a thickness of about 0.2 mm. One surface of each of these protective members 12.13, 2a, 1.3a is thermally fused to two opposing surfaces 11a, llb of the laser medium 11 in the thickness direction. The other surfaces of these protective members 12 and 1.3 constitute the reflective surfaces 10a and 10a of the slab laser medium 10, respectively. In this embodiment, the refractive index of these protection members 12, 1.3 is 1.5 at wavelength.
For light of 0.06 μm, it is 1.54.527, and the coefficient of thermal expansion is 103, OX 10′/′C. That is, both the refractive index and the thermal expansion coefficient have values extremely close to those of the laser medium base 11. In addition, these protective members 1.2.13 are rated at 95% for light in the Nd absorption wavelength band.
% transmittance. Furthermore, these protection members 12
．． No. 13 has extremely superior water resistance compared to phosphate glass. That is, the weight loss due to the powder method is only 0.03%, compared to 0.1% for phosphate. Here, the powder method refers to taking a predetermined amount of glass powder that has been ground to a predetermined particle size in a mortar, adding water to it, heating it, drying it, and weighing it to reduce the weight. is expressed as a percentage. Note that the silicate glass constituting these protective members 12, 1.3 may contain a laser active substance such as Nd. However, in that case, it becomes a two-wavelength laser medium.

The slab-type laser medium of the embodiment described above can be manufactured, for example, by the following procedure.

(a) Phosphate glass containing 8.7 wt% of Nd ions, which is a laser active substance, is 10 mm thick, 30 mm wide,
One plate-shaped laser glass body having a length of 160 mm is prepared.

(b) Silicate glass with a thickness of 7 mm and a width of 30 mm,
Two plate glass bodies each having a length of 160 mm are prepared.

(c) Two surfaces of the phosphate laser glass body facing each other in the thickness direction and one surface of each of the two silicate glasses are polished to a surface precision of λ/2.

(d) Wash the three plate-shaped glass bodies with a cleaning machine used for cleaning semiconductors, etc., and place the 1-sheet of phosphate glass bodies into two sheets with the polished surfaces in contact with each other. The three glass bodies are stacked by sandwiching them between the silicate glass bodies. As a result, the contact surface of each glass body is λ
Since they are polished to a high precision of /2, they are in condition to be optical contactors.

(e) The laminated glass bodies are held at 500° C. for 48 hours, and the three glass bodies are thermally fused and integrated.

(f) Two opposing surfaces in the J-width direction of the integrally formed glass body are polished so that the thickness of the silicate glass body becomes approximately 0.12 mm, and the surface accuracy of both surfaces is λ/2, so that the parallelism on both sides is 10 seconds.

(g) Next, both longitudinal end surfaces of the glass body are polished. In this polishing, the two end faces are parallel and the angle α between the two ends and the surface in the thickness direction is α-146.92°. In that case, the degree of area is λ/2, and the parallelism of both end faces is 23 seconds. As a result, two slab-type laser media 10 can be obtained.

Next, an example of laser oscillation using the slab type laser medium 10 of this embodiment will be described.

As shown in FIG. 3, the slab type laser medium 10
A resonant mirror 3 whose reflecting surfaces are parallel to each other
Placed between 1 and 32. In this case, the reflective surfaces of the slab laser medium 10], Oa, and 10b are perpendicular to the reflective surfaces of the resonant mirrors 31 and 32, and
The positions are set so that the light reflected by these resonant mirrors 31 and 32 enters and exits through the center of the entrance and exit surfaces 10c and 10d of the slab type laser medium 10.

The resonant mirror 3] transmits light with a wavelength of 1.06 μm to 100 μm.
The resonant mirror 32 is one that reflects 70% of light with a wavelength of 1.06 μm.

Further, the reflective surfaces 10a, 1 of the slab type laser medium 10
Excitation light sources 21 and 22 are placed outside facing 0b. As the excitation light sources 21 and 22, Xe flash lamps are used.

Further, the cooling water W is made to flow so as to directly contact the reflecting surfaces 3 10a and 10b of the slab type laser medium]-◯.

In the above configuration, the excitation light source 21. ．． On 22]
- 10Hz energy at 100OJ per pulse 3
An oscillation test was performed in addition to the time. As a result, it is not possible to stably obtain pulsed laser light with an average output of 80W.

In addition, when the slab of the above-mentioned example was brought into contact with the reflective surfaces 1.0a and 10b of the laser medium O for 1188 hours, and this was continued for 3 months, it was taken out and observed under a microscope. No changes were observed. That is, it was confirmed that the slab type laser medium 10 of this example had sufficient water resistance.

In the above embodiment, the protective member is fixed to the base of the laser medium by heat fusion, but depending on the case, it may be bonded using an adhesive.

This eliminates the need for thick polishing after heat-sealing in order to increase the area of the glass body serving as the protective member, unlike in the case of heat-sealing, making it possible to save on materials.

4 On the other hand, there is a risk of bubbles forming during adhesion, and it is not possible to achieve adhesion as strong as heat fusion without interfacial loss, and the adhesive is easily deteriorated by TJV light or laser light. However, it cannot be denied that the durability is inferior to that of heat fusion.

Further, although the thickness of the protective member was set to 0.2 mm in the above embodiment, it may be within the range of O11 to 0.3 mm. Furthermore, in order to reduce Fresnel reflection at the fixed surface between the protective member and the base of the laser medium, it is advantageous to have a smaller difference in their refractive indexes;
．． It is sufficient to select any value in the range 5 to 1.6. Furthermore, the smaller the difference in thermal expansion, the better.
Practically speaking, it is sufficient that the difference in thermal expansion is within ±5×10'/°C.

[Effects of the Invention] As detailed above, the present invention has the following features: Laser resonant light traveling in a plate-shaped laser medium is alternately reflected by two opposing surfaces to travel in a zigzag pattern. 5. A slab-type laser medium that performs laser oscillation by oscillating a laser beam, the laser medium having a plate-shaped base made of laser glass, and a glass having superior water resistance compared to the laser glass constituting the laser medium base. A protection member formed in a thin plate shape from a material and integrally formed with the laser medium base by fixing one surface of each to the outer surface of two opposing surfaces of the laser medium base. As a result, a slab-type laser medium that can be cooled by bringing water into direct contact with the laser medium is obtained with a relatively simple configuration.

[Brief explanation of the drawing]

FIG. 1 is a perspective view of a slab type laser medium according to an embodiment of the present invention, FIG. 2 is a sectional view taken along the line II-n of FIG. 1, and FIG.
The figure is an explanatory diagram of an example of use of one embodiment. DESCRIPTION OF SYMBOLS 10... Slab type laser medium, 11... Laser medium base, 12, 1.3... Protective member.

Claims (1)

[Claims] A slab-type laser medium that performs laser oscillation by causing laser resonant light traveling in a plate-shaped laser medium to alternately reflect on two opposing surfaces and travel in a zigzag pattern. a laser medium base formed in a plate shape of laser glass; and a thin plate formed of a glass material that is more resistant to water than the laser glass constituting the laser medium base; A slab-type laser medium having a protective member formed integrally with the laser medium base by fixing one surface of each to the outer surface of two opposing surfaces of the slab-type laser medium.