JPS62160779A - Gas laser apparatus - Google Patents

Abstract

PURPOSE:To avoid entry of atmosphere into a laser resonator and to remove contamination on the inner surface of a mirror readily even in a structure, from which the laser mirror cannot be removed, when the contamination of the laser mirror is removed, by removing the contamination by etching utilizing discharge from a discharge electrode provided in the laser resonator without detaching the laser mirror from the resonator. CONSTITUTION:When a total reflection mirror, which is attached to a laser resonator 1 or an output window (laser mirror M) is contaminated, a valve 2 is opened, and laser gas in the resonator 1 is exhausted by an exhausting pump (d). After the valve 2 is closed, a valve 3 is opened, and etching gas (e) is introduced in the resonator 1. As the etching gas, e.g., CCl4, CCl2F2, CF4, NF3 and the like are used. It is desirable that a pressure range of several Pa - several hundred Pa is used. Discharge is generated between a mesh electrode 6 facing the contaminated surface of the laser mirror M and the resonator 1. Then the gas in the vicinity of the mesh electrode 6 is converted into plasma, and the contamination of the laser mirror M is etched with ions.

Description

[Detailed description of the invention] (Technical field of invention) The present invention relates to a gas laser device.

(Background of the invention) FIG. 2 is an example of a conventional gas laser resonator.

(Hereinafter, the gas laser will be simply referred to as a laser.) Total reflection mirror Mr, partial transmission mirror or output window M.

A laser gas is sealed in a laser resonator 1 equipped with a laser mirror (hereinafter referred to as a laser mirror).

Light excited by an excitation source (not shown) causes laser oscillation between the laser mirrors and exits from the output window Mo. (Output light is indicated by an arrow) In FIG. 2, the reflection surface of the total reflection mirror Mr is shown as an outer surface, but it may be an inner surface.

However, during laser oscillation, impurities generated or mixed into the laser gas adhere to the inner surface of the laser mirror, and when the laser beam is irradiated onto this, the impurities become particles or films and stick to the inner surface. It becomes dirty.

This contamination is hereinafter referred to as "optical element contamination." Since most of this optical element contamination is opaque to the laser wavelength, it has been a cause of a decrease in laser output. In addition, even if the transparent optical element is dirty, the laser beam will be scattered. Deterioration of beam divergence angle and beam cross-section swelling,
It was the cause.

Therefore, it is necessary for conventional gas lasers to have a structure in which the laser mirror can be replaced, and to replace it with a clean laser mirror when the dirt becomes severe. However, when replacing the laser mirror, if the atmosphere mixes with the laser gas in the resonator 1, the laser oscillation becomes impossible or the efficiency decreases, so mixing of the atmosphere must be avoided at all costs. Therefore, the internal pressure of resonator 1 must always be kept higher than atmospheric pressure, and the laser gas must be replaced while flowing out through the hole after removing the laser mirror, or the inside of the laser resonator, which is contaminated with air, must be replaced several times. Measures were also taken to replace the remaining atmosphere with laser gas and reduce the amount of air remaining. However, this method requires a large amount of laser gas, the mechanism for replacing the laser mirror becomes complicated, the overall size of the device increases, and the optical axis of the laser mirror after replacement is disadvantageous. Since it has the disadvantage of requiring adjustment, relatively inexpensive lasers are of a sealed type, and the laser mirror (window in the case of an external mirror type) and resonator are integrated, and when the optical element becomes dirty, , and the lifespan of the laser device.

(Objectives of the Invention) An object of the present invention is to solve the drawbacks of conventional treatment methods for gas laser stains on optical elements, and to provide a gas laser device having a function of removing stains on optical elements.

(Embodiment) FIG. 1 shows a first embodiment of the present invention, and only shows the vicinity of the total reflection mirror or the output window. Figure 1(a) is shown in Figure 1(a).
It is a CC arrow sectional view of b).

When the total reflection mirror or output window (hereinafter simply referred to as laser mirror M) attached to the laser resonator 1 becomes dirty, the dirt is removed in the following order. (i) Open valve 2,
The laser gas inside the resonator 1 is exhausted by an exhaust pump. (ii) After closing valve 2, valve 3 is opened and etching gas is introduced into resonator 1. The etching gas is, for example, CCβ4, CC1z F2, CF4, N
It is preferable to use F3 or the like and set the pressure in the range of several Pa to several 100 Pa. (iii) By causing a discharge between the mesh electrode 6 facing the dirty surface of the laser mirror M and the resonator 1, the gas near the mesh electrode 6 turns into plasma, and ions etch the dirt on the laser mirror M. . In this case, the discharge may be a direct current discharge or a high frequency discharge. The power supplied from the power source 5 varies depending on the area of the mesh electrode 6, but the power density per area is 0.1
~IW is required. (iv) Once the dirt has been removed,
After stopping the discharge, valve 3 is closed and valve 2 is opened to exhaust the etching gas. If the residual etching gas has a large effect on laser oscillation, it is desirable to open the valve 4 and perform passivation with the laser gas. (
v) Finally, the laser resonator 1 is filled with laser gas at a predetermined pressure.

The above is the procedure for removing dirt from a laser mirror.

During laser oscillation, if the mesh electrode 6 has a thin mesh wire diameter, there is no problem because it hardly blocks the laser output beam. If the mesoche pattern is made into an irregular mesh pattern instead of a regular grid pattern, interference speckles can be prevented from occurring in the output beam.

FIG. 3 shows a second embodiment of the invention. FIG. 3(a) is a sectional view taken along the line DD in FIG. 3(b).

Except for the aperture-shaped electrode 7, this embodiment is the same as the first embodiment, and the operation up to the removal of dirt on the laser mirror M is also the same. However, when removing dirt on the laser mirror M by electric discharge, the aperture-shaped electrode 7 is used in a fully closed state as shown in FIG. , does not block the laser beam at all. The opening and closing of the aperture-shaped electrode 7 is remotely controlled by an appropriate method, such as mechanical operation from outside the resonator l or electromagnetic drive attached to the aperture-shaped electrode 7.

Figure 4 shows the third embodiment in which the discharge electrode is a flip-up electrode 8, which is set at position A only when discharging to remove dirt from the laser mirror M, and set at position B during laser oscillation. Therefore, it does not interfere with the laser beam. The discharge groove 8 may be plate-shaped or mesh-shaped.

FIG. 5 shows a fourth embodiment in which the discharge electrode is a vertically movable electrode 9.
It has become. Power is supplied to the discharge pole 9 through the bellows 10, so it is set at position A during discharge and at position B during laser oscillation. However, Figures 4 and 5
In the figure, valves 2 to 4 are omitted.

FIG. 6 shows a fifth embodiment of the present invention. Gate valve G
The configuration is the same as that of the first embodiment except that the resonator can be isolated into 1 and 1'' by V.

If the laser mirror M becomes dirty, (i) close the gate valve GV and isolate the resonators 1 and 1'.

After this, evacuation, introduction of etching gas, etching of dirt, evacuation, and filling of laser gas are performed, and the gate valve GV is opened again to enable laser oscillation. When removing dirt from the laser mirror M as described above, by closing the gate valve GV, only the small volume of laser gas present in the resonator 1 can be discarded without discarding the laser gas in the resonator 1. Since the objective can be achieved, laser gas can be saved. Also, other valve types (for example, a butterfly valve) can be used instead of the gate valve G■.

FIG. 7 shows a sixth embodiment of the present invention. The gate valve electrode GE isolates the resonator into parts 1 and 1, and the gate part also serves as a discharge pole. However, the gate portion is electrically insulated from the resonator 1 (1'). During discharge to remove dirt from the laser mirror M, the gate valve electrode GE is closed and the same operation as in the fifth embodiment is performed.

Of course, the gate should be open during laser oscillation.

(Effects of the Invention) As described above, according to the present invention, when removing dirt from a laser mirror, etching can be performed by electric discharge using a discharge scraper provided in the laser resonator without removing the laser mirror from the resonator. Since dirt is removed by the laser resonator, it is possible to prevent air from entering the laser resonator, and even if the laser mirror cannot be removed, dirt can be easily removed from the inner surface of the mirror, making it easy to maintain the purity of the laser gas. Since the laser mirror does not move, there is no need to adjust the optical axis, and the need for replacement gas and laser gas can be saved, which saves the effort, time, and cost of removing dirt from the laser mirror.The seal has a simple structure. Although it is a cutting gas laser, it can remove dirt on mirrors, so it has the advantage of a long device life.

[Brief explanation of drawings]

FIG. 1 is a diagram showing a first embodiment of the present invention, FIG. 2 is a schematic sectional view showing a conventional gas laser, and FIGS. 3 to 7 are diagrams showing second to sixth embodiments of the present invention. (Explanation of symbols of main parts) 1: Laser resonator 2 to 4: Valve filter 5: Discharge radio wave 6: Mesh electrode 7: Squeezed electrode 8: Flip-up type electrode 9: Vertically movable electrode 10: Bellows 6 M: Laser mirror MO: Output window Mr: Total reflection mirror Gv: Gate valve GE: Gate valve electrode

Claims (1)

[Scope of Claims] 1) A gas laser device characterized in that a discharge electrode for removing dirt from an optical element is provided near the laser mirror. 2) The gas laser device according to claim 1, wherein the discharge electrode is a fixed mesh electrode. 3) The gas laser device according to claim 1, wherein the discharge electrode is a constricted electrode. 4) The gas laser device according to claim 1, wherein the discharge electrode is a movable electrode.