JP2735063B2 - Gas laser tube - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a gas laser tube, and more particularly to the structure of a gas laser tube using an X-cut quartz plate for a Brewster window.

[0002]

2. Description of the Related Art A gas laser tube has a low-pressure gas such as argon, helium, or neon sealed in an airtight container.
In recent years, the use of such oscillating light, such as medical equipment, printers, experimental light sources, and plate making, has been increasingly used. Also, as a recent trend, high output ultraviolet light (wavelength of about 3
(50 nm or less) is increasing.

FIG. 3 shows a typical example of such a gas laser tube. The Brewster windows 32a and 32b (hereinafter, referred to as windows) are composed of a discharge path thin tube 31, an anode, and a cathode 3
6 are hermetically bonded with glass or the like to the ends of Brewster valves 33a and 33b attached to both ends of an airtight container 30 containing therein. A reflection mirror 34 and an output mirror 35 are provided outside the gas laser tube, respectively, with Brewster windows 32a and 32, respectively.
2b.

A rare gas of several tens Pa, for example, argon, krypton, or the like is sealed in the hermetic container, and a voltage is applied between the cathode 36 and the anode 37 to cause gas discharge. The discharge light oscillates reciprocatingly in the optical resonator constituted by the mirrors 34 and 35, and the light of the specific wavelength is amplified to become the laser light 38, which is emitted from the output mirror 35 side.

The Brewster windows 32a and 32b are generally made of optical glass or quartz glass material, and have a Brewster angle with respect to the optical axis (about 34 in the case of quartz glass).
By tilting only by (°), anisotropy occurs in the reflection loss due to the phase angle of light, transmission and amplification of light having a specific phase component occur, and laser light having strong linear polarization can be obtained. However, since the windows 32a and 32b are irradiated with the above-described high-power ultraviolet light, optical deterioration of the window glass occurs, which causes a problem of lowering the laser output and causing a poor optical mode. .

As a countermeasure for this, recently, an attempt has been made to use quartz (single crystal of SiO ₂ ), which is more stable than glass, for the window. However, quartz, which is a crystal material, has significantly different mechanical properties, that is, physical properties such as Young's modulus, strength and thermal expansion coefficient, depending on the crystal axis direction. FIG. 6 shows the relationship between the crystal axis and the thermal expansion. For this reason, when joining a window to a Brewster valve, various measures are required. For example, JP-A-58-
No. 223384, with the aim of increasing the reliability of the hermetic bonding of the epoxy resin adhesive used as a conventional technique, the window bonding surface of the Brewster valve was
A metal oxide layer is sequentially deposited to have a composition and a thickness so as to finally have a glass composition ratio for bonding. It has been proposed that the glass bonding layer be made as thin as possible by overlapping and heating the windows, thereby minimizing the influence of the stress generated due to the difference in thermal expansion.

FIG. 4 is a quotation of the structure of the Brewster window portion shown in US Pat. No. 4,677,640, in which a Brewster window 11 made of a Z-cut quartz crystal having small anisotropy is used. One end face of the bulb 12 is hermetically joined with a seal glass 13. Further, the other end of the Brewster valve is also a Z-cut surface, and the metal tubular part 14 is air-tightly joined to this with another sealing glass 15. These are joined to the end metal part 16 of the gas laser tube by brazing or the like, and the Brewster window is attached to the gas laser tube.

FIG. 5 is a view showing a cross-sectional structure near a Brewster window of another gas laser tube using an X-cut quartz window. Here, the Brewster window 21 is hermetically bonded to a crystal Brewster valve 22 having an X-cut surface with a seal glass 23. On the other hand, Brewster valve 22
Is formed with a flange 22a at the other end, and its end face is perpendicular to the laser light (tube) axis as shown in the figure. This end face is optically polished, and is mechanically and airtightly bonded to the end metal part 26 of the laser tube via an annular indium (In) foil 27. Parts 28a and 28b are opposed metal flanges which are fastened and fixed by bolts 28c. The reason why indium 27 is used as the hermetic bonding material is to avoid a mismatch in the thermal expansion relationship between the end metal part 26 and the quartz flange (22a).

[0009]

However, the structure of the gas laser tube using the above-described conventional quartz plate for the Brewster window has the following disadvantages.

(1) Since the X-cut quartz plate has directionality, there is a limitation that the mating part to be joined is also X-cut. If this is neglected, breakage such as cracks is likely to occur.

(2) The Z-cut quartz plate has good isotropic in-plane thermal expansion characteristics, but has a practical problem that it takes time to stabilize the output characteristics and the like of the laser tube. Although the cause of this phenomenon is not clear yet, it is considered that the thickness direction of the optical face plate is the Z-axis direction having a large coefficient of thermal expansion and is easily affected by the temperature drift of the laser tube itself and the laser oscillator.

(3) In the above-mentioned mechanical hermetic bonding using indium, the heat resistance of the bonding structure is higher than the melting point of In (156).
° C), which is about 200 ° C or more lower than that of glass bonding. To this extent, the heating for outgassing became insufficient, and the cleanliness of the gas in the pipe deteriorated, and there was a problem that the life was naturally shortened.

[0013]

According to the present invention, a discharge path thin tube is provided in an airtight container, and a Brewster valve and a Brewster window arranged coaxially with the tube axis of the discharge path thin tube are provided at the end of the airtight container. In a gas laser tube which is airtightly joined, the Brewster window is made of an X-cut quartz plate, the Brewster valve is made of a quartz tubular member, and the Brewster valve has a joint surface with the Brewster window. An X-cut surface is used, and a joint surface with the airtight container is a Z-cut surface.

A metal tubular part having a coefficient of thermal expansion similar to that of Z-cut quartz is disposed between the Z-cut surface of the Brewster valve and the airtight container, and the Brewster valve and the metal tubular part are fritted with glass. And are hermetically bonded. As the material of the metal tubular component, Monel, cupronickel, 42% Ni-6% Cr-remainder Fe alloy, stainless steel, soft magnetic iron, nickel, etc. are used.

[0015]

Next, the present invention will be described with reference to the drawings. FIG. 1 is a sectional view of a Brewster window of a gas laser tube according to a first embodiment of the present invention and the vicinity thereof. Reference numeral 1 denotes a Brewster window (hereinafter, referred to as a window) made of an elliptical X-cut quartz plate having a major axis of 18 mm, a minor axis of 10 mm, and a thickness of 1 mm. The window 1 has a major axis direction parallel to the Z axis and a minor axis direction parallel to the Y axis (perpendicular to the X axis and the Z axis). Reference numeral 2 denotes a Brewster valve made of a quartz cylinder having an outer diameter of 12 mm and an inner diameter of 7 mm. One end face is 32.66 ° with respect to the tube axis, and the other end face is 122.
It is cut and polished at an angle of 66 °. At this time,
Since the 2.66 ° plane was selected to be perpendicular (X cut) to the X axis of the crystal axis, the other end (122, 66 ° plane) was automatically perpendicular to the Z axis and to the X and Y axes. It is parallel (Z cut). Both surfaces were polished to a flatness of λ / 10 or less.

Next, an electromagnetic soft iron plate was pressed to prepare a metal tubular part 4a having a flange at one end. This part was located at one end of the airtight container of the gas laser tube main body in a later step, and was joined by TIG welding 7 to an end metal part 6a made of Kovar alloy having the same dimensions as the flange of the metal tubular part 4a.

In assembling and joining the Brewster window 1, first, the Z-cut surface of the Brewster valve 2 (122.
A paste of seal glass (# 7575, manufactured by Iwaki Glass Co., Ltd., coefficient of thermal expansion: 89 × 10 ⁻⁷ / ° C.) is applied to the (66 ° plane). Similarly, a metal tubular part 4a having the tip coated with the sealing glass paste is fixed concentrically with a butt jig (not shown). The Brewster valve 2 and the metal tubular part 4a thus combined were heated at 450 ° C. for 40 minutes to melt and crystallize the # 7575 seal glass 5, and then cooled to obtain a Brewster window assembly.

Next, this assembly is fixed to a jig (not shown) which holds the assembly at an angle so that the X-cut surface is horizontal. A Brewster window 1 of X-cut quartz is placed on the Brewster surface (X-cut surface) of Brewster valve 2 on this assembly.
An elliptical glass sintered body made of another seal glass 3 (LS-0111M, manufactured by NEC Corporation, having a coefficient of thermal expansion of 50 × 10 ⁻⁷ / ° C.) and circumscribing the window 1 was used for the window 1. Put around. These assemblies were heated in an electric furnace at 460 ° C. for 10 minutes to melt the seal glass 3 and then cooled to produce a Brewster window.

Next, the Brewster window manufactured as described above is attached to the end metal parts 6a made of Kovar alloy with flanges attached to both ends of the gas laser tube manufactured separately as described above. Were brought into close contact with each other, and the periphery thereof was hermetically joined by argon arc welding. The other end of the gas laser tube was similarly airtightly joined to the Brewster window. This process completes the sealed tube of the gas laser tube,
Thereafter, through the same steps as in the prior art, after evacuation and gas charging, the exhaust pipe was closed to complete the gas laser tube.

FIG. 2 is a sectional view of a Brewster window of a gas laser tube and its vicinity according to a second embodiment of the present invention. The Brewster valve 2 is the same as the first embodiment, and is a quartz tubular component having one end face having an X-cut face and the other end face having a Z-cut face. A metal tubular part 4b made of a 42% Ni-6% Cr-Fe alloy, which is fitted with the outer peripheral surface with a clearance of 0.2 mm, was hermetically joined to the Z-cut side of the Brewster valve 2 with a # 7575 seal glass 5.

Next, the other end of the metal tubular part 4b was brazed to the end metal part 6b of the gas laser tube using a high-frequency induction heating brazing apparatus using silver-copper alloy brazing (not shown). Then, the Brewster valve 2, the metal tubular part 4b, and a part of the end metal part 6b of the hermetic container are inserted, and
The assembly was placed in an electric furnace in a nitrogen atmosphere such that the X-cut surface of Brewster valve 2 was horizontal. Next, the Brewster window 1 is placed on the Brewster valve 2, a glass sintered body made of LS-0111M sealing glass 3 is placed around the Brewster window 2, and heated at 460 ° C. for 10 minutes to heat the Brewster window 1. And the Brewster valve 2 were hermetically joined. Thereafter, a gas laser tube was completed in the same manner as described in the first embodiment.

[0022]

The gas laser tube manufactured as described above has been confirmed to be superior to the conventional structure in the following points. (1) X-cut quartz can be used for the window, and the initial stabilization time of the laser beam output is about 1/3 of that of the conventional Z-cut window. (2) Hard seal made of glass at the hermetic joint Can be adopted, the reliability of the seal has been improved, and the gas discharge heating at the time of exhaustion can be increased to 300 ° C. or more, so the gas emission in the pipe decreases,
The (3) Brewster valve, which has a longer life,
The function of converting the anisotropy such as the thermal expansion characteristic in the crystal axis direction has been provided, so that the design of the gas laser tube has been simplified.

[Brief description of the drawings]

FIG. 1 is a sectional view of a Brewster window according to a first embodiment of the present invention.

FIG. 2 is a sectional view of a Brewster window according to a second embodiment of the present invention.

FIG. 3 is a schematic diagram showing a configuration of a conventional gas laser oscillator.

FIG. 4 is a cross-sectional view of a Brewster window of a conventional gas laser tube.

FIG. 5 is a cross-sectional view of a Brewster window of another conventional gas laser tube.

FIG. 6 is a graph showing the temperature change of the thermal expansion coefficient of the crystal in the X, Y and Z axis directions.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Brewster window 2 Brewster valve 3, 5 Seal glass 4a, 4b Metal tubular part 6a, 6b End metal part

Claims (3)

(57) [Claims] A blast tube and a Brewster window disposed coaxially with a tube axis of the discharge path thin tube are hermetically joined to at least one end of the airtight container. In a gas laser tube that is
The Brewster window is made of an X-cut quartz plate, and the Brewster valve is made of a quartz tubular member. The Brewster valve has an X-cut surface at the joint surface with the Brewster window, and the airtight container. A gas laser tube, characterized in that a joining surface of the gas laser tube is a Z-cut surface. 2. A metal tubular part having a coefficient of thermal expansion similar to that of Z-cut quartz is disposed between the Z-cut surface of the Brewster valve and the hermetic container. 2. The gas laser tube according to claim 1, wherein said gas laser tube is hermetically bonded with frit glass. 3. The material of said metal tubular part is Monel, cupronickel, 42% Ni-6% Cr-remaining Fe alloy,
The gas laser tube according to claim 2, wherein the gas laser tube is any one of 18% Cr-Fe alloy, stainless steel, soft magnetic iron and nickel.