JPH06216436A - Gas laser device - Google Patents

Abstract

PURPOSE:To provide a gas laser device in which of the oscillation waves generated by the main discharge of the main electrode, the oscillation waves in the direction of the optical axis of an optical resonator can efficiently be attenuated. CONSTITUTION:The device comprises an optical resonator in which an output mirror 14 and a high-reflection mirror 15 are so placed as to oppose to each other, a main electrode consisting of a cathode 2 and an anode 3 which are so placed in the optical resonator as to be spaced apart from each other in a direction perpendicular to the optical axis of the optical resonator, and a plurality of oscillation absorbing plates 17 disposed at gradually changing intervals along the optical axis at least in one of the spaces between one end of the main electrode of the optical resonator and the output mirror and between the other end of the main electrode and the high-reflection mirror.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a gas laser device which excites a gas laser medium and outputs laser light.

[0002]

_2. Description of the Related Art Gas laser devices include TEACO ₂ lasers and excimer lasers of the high pressure lateral discharge excitation type. Such a gas laser device uses CO as a gas laser medium.
He or Ne is used as a buffer gas for a mixed gas of ₂ , ₂ , N ₂ or He or a mixed gas of a rare gas such as Kr or Xe and a halogen such as F ₂ or HCl.

The gas laser medium is circulated in the laser tube, and is circulated in the main discharge space between the main electrodes composed of the cathode and the anode arranged in the circulation path at right angles to the flow direction. A high voltage is applied to the main electrode to generate a main discharge, and the main discharge excites a gas laser medium in the main discharge space to generate laser light.

The laser light generated between the pair of main electrodes is amplified by an optical resonator composed of an output mirror and a high-reflection mirror arranged on both ends of the main electrode in the longitudinal direction, and the output mirror is output.
Is oscillated and output from.

When a main discharge is generated between the main electrodes, it is inevitable that a vibration wave such as an acoustic wave or a shock wave is generated between the pair of main electrodes due to the discharge. This vibration wave is generated in various directions, and in particular, the vibration wave generated in the optical axis direction of the optical resonator formed by the output mirror and the highly reflective mirror is reflected back and forth by the mirror of the optical resonator, It ’s hard to disappear, so
Fluctuations occur in the density of the gas laser medium in the main discharge space.

When the density of the gas laser medium fluctuates, the main discharge becomes nonuniform in accordance with the change in the density, and the density becomes coarse. Therefore, the main discharge cannot be performed at high repetition rate due to the density, and a high output laser is obtained. -The light may not be able to oscillate.

[0007]

As described above, in the conventional gas laser device, fluctuations occur in the gas laser medium in the main discharge space due to the vibration waves generated in the optical axis direction of the optical resonator. Fluctuations have sometimes caused a reduction in laser output.

The present invention has been made in view of the above circumstances. An object of the present invention is to provide a gas laser device capable of promptly attenuating a vibration wave generated in the optical axis direction of an optical resonator. To provide.

[0009]

SUMMARY OF THE INVENTION In order to solve the above problems, the present invention provides an optical resonator in which an output mirror and a high reflection mirror are arranged to face each other, and an optical axis in the optical resonator. Between a main electrode composed of a cathode and an anode arranged apart from each other in a direction intersecting with the direction, between one end of the main electrode and the output mirror in the optical resonator, or the other end of the main electrode and a high reflection mirror. And a plurality of vibration absorbing plates arranged with gradually changing intervals along the optical axis direction in at least one of the space portions between and.

[0010]

According to the above construction, the vibration wave generated in the optical axis direction of the optical resonator is attenuated by the vibration absorbing plate and the distance between the vibration absorbing plates is changed. It is possible to damp vibrations in different frequency bands, that is, damp vibrations in a wide range of frequency bands.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. The gas laser device shown in FIG. 1 and FIG.
The laser tube 1 is filled with a gas laser medium for excimer laser, which is made of Cl, Ne or He. The laser tube 1 has an airtight structure having a circular cross section, and a cathode 2 and an anode 3 forming a main electrode are opposed to each other at a predetermined interval in the axial direction of the laser tube 1. It is arranged along. These electrodes 2 and 3 are connected to a DC high voltage power source 5 via a thyratron 4 as shown in FIG. A main capacitor 6 is connected in parallel to the DC high voltage power supply 5.

A blower 7 and a heat exchanger 8 are arranged in the gas laser pipe 1 as shown in FIG.
The gas laser medium is supplied to the cathode 2 and the anode 3 by the blower 7.
The heat exchanger 8 cools the gas laser medium whose temperature has risen due to the main discharge, which will be described later.

On the other hand, on both sides of the cathode 2 and the anode 3,
As shown in FIG. 2, a pair of upper pin electrodes 11a and lower pin electrodes 11b, which are opposed to each other in the vertical direction and are opposed to each other, are arranged at predetermined intervals along the longitudinal direction of the main electrode. ing. The pin electrodes 11a and 11b are connected to the DC high-voltage power supply 5 via the thyratron 4, and the upper pin electrode 11a is connected to the peaking capacitor 1
It is connected to the DC high voltage power source 5 via 2.

Therefore, when the thyratron 4 is turned on by a trigger signal from a control unit (not shown), the charge charged in the main capacitor 6 is changed to the peaking capacitor 1.
Since the transition to No. 2, spark discharge is ignited between the upper pin electrode 11a and the lower pin electrode 11b. As a result, the main discharge space 9 between the cathode 2 and the anode 3 is preionized by the ultraviolet rays. When the preliminary ionization of the main discharge space 9 progresses, the main discharge is ignited between the cathode 2 and the anode 3,
The main discharge excites the gas laser medium to generate laser light.

A first tube body 12 and a second tube body 12 are provided at portions of both end surfaces in the axial direction of the laser tube 1 corresponding to the main discharge space 9.
One end of each tube body 13 is attached airtightly.
An output mirror 14 is airtightly attached to the other end of the first pipe body 12, and the output mirror 14 is attached to the other end of the second pipe body 13.
A highly reflective mirror 15 which forms an optical resonator is also mounted in an airtight manner.

Inside the tubes 12 and 13, a plurality of rectangular through holes 16 through which the laser light L generated in the main discharge space 9 passes are formed. A single vibration absorbing plate 17 is held between these peripheral portions via a plurality of cylindrical spacers 18. The spacer 18 is made of an elastic material such as rubber, a porous material, a material easily absorbing vibration such as a nickel wire mesh or alumina fiber, and the vibration absorbing plate 17 is an aluminum or nickel plate or a nickel porous material. It is also made of a material such as a plate that easily absorbs vibration.

As shown in FIG. 3, four vibration absorbing plates 17 are provided.
If the distances from the main electrodes 2 and 3 to the mirrors 14 and 15 are P1 to P3, the distance is, for example, 2
By expanding by mm, P1 <P2 <P3 (P1 = 2 mm,
(P2 = 4 mm, P3 = 6 mm). That is,
The thickness (length) of the spacer 18 provided between the vibration absorbing plates 17 is set so as to satisfy the above relationship.

In the gas laser device having the above structure, the thyratron 4 is turned on to ignite a spark discharge between the upper pin electrode 11a and the lower pin electrode 11b, and ultraviolet rays generated at that time cause a main discharge space. When part 9 is preionized, a main discharge is ignited between cathode 2 and anode 3. As a result, the gas laser medium circulating in the main discharge space 9 is excited and laser light L is generated.

The laser light L generated in the main discharge space 9 is repeatedly reflected and amplified by the high reflection mirror 15 and the output mirror 14 of the optical resonator, and is oscillated and output from the output mirror 14. .

When the main discharge is ignited between the cathode 2 and the anode 3, acoustic waves and shock waves are generated at that time. These velocities are Xe, HCl, He as the laser gas medium.
It is about 100 m / s in the gas for exim maleizer consisting of. Of the acoustic waves and shock waves generated along the optical axis direction of the optical resonator, a part of them is the pair of main electrodes 2, 3 described above.
When it passes through the through hole 16 of the vibration absorbing plate 17, the other part wraps around in the direction of the spacer 18 as shown by the arrow in FIG. It is absorbed by the spacer 18.

The frequency wave of the acoustic wave is 2 cm for each electrode design.
Then, about 50 will be reflected and propagated.
KHz, if the distance between the optical resonators composed of two mirrors 14 and 15 is 1 m, the one that resonates there is 1 KHz.
Met. In addition, an acoustic wave of 50KH that is a positive multiple of the above frequency
z, 100 KHz, 150 KHz, ... and 1 KHz, 2K
Hz and 3 KHz were also observed.

The vibration wave passing through the through holes 16 is sequentially attenuated by the vibration absorbing plates 17 and the spacers 18 by successively passing through the through holes 16 of the plurality of vibration absorbing plates 17, and the output mirror is output. When it reaches 14 or the high reflection mirror-15, it will be considerably attenuated. Therefore, since the vibration wave generated in the main discharge space 9 is hardly reflected by the mirrors 14 and 15 and returns to the main discharge space 9 again,
Fluctuation does not occur in the gas laser medium in the main discharge space 9.

Moreover, since the distance between the vibration absorbing plates 17 is set to be larger by 2 mm in the direction of the mirrors 14 and 15, vibrations of different frequencies are generated depending on the change in the distance between the vibration absorbing plates 17. Be absorbed. That is, in this embodiment, the interval is gradually widened,
As the interval becomes wider, it is possible to absorb vibration in a low frequency band.

FIG. 5 shows that due to the main discharge, acoustic vibration exists in the main discharge space 9 in a wide frequency band of 10 kHz to 1 MHz. Then, the acoustic vibration is 0 to 100 k in the interval P1 of 2 mm formed by the first and second vibration absorbing plates 17 located on the end sides of the main electrodes 2 and 3.
It resonates with vibrations up to Hz, damps the vibrations, and is 10 at a 4 mm interval P2 formed by the second and third vibration absorbing plates 17.
Vibrations of 0 to 500 kHz resonate and attenuate the vibrations. Further, it was measured that at a distance P3 of 6 mm formed by the third and fourth vibration absorbing plates 17, the vibration resonates with the vibration from 500 kHz to 1 MHz and attenuates the vibration. That is, by gradually increasing the distance between the plurality of vibration absorbing plates 17, it is possible to damp vibration waves having frequencies over a wide range. The resonance frequency at each interval varies depending on various conditions such as the material of the vibration absorbing plate 17.

FIG. 6 shows the results of measurement of the relationship between the magnitude of the oscillating wave and the repetition rate of pulse oscillation in the gas laser device of the present invention and the conventional gas laser device. The straight line A in the figure shows the present invention and the straight line B shows. Indicates conventional. According to the present invention, it was confirmed that the magnitude of the vibration wave was sufficiently smaller than the conventional one, even if the number of repetitions increased.

FIG. 7 shows the relationship between the laser output and the number of repetitions in the gas laser device of the present invention and the conventional gas laser device. Curve A
It has been confirmed that, according to the present invention shown by, the number of repetitions is increased and a high laser output can be obtained as compared with the conventional case shown by the curve B.

In the above embodiment, the interval between the plurality of vibration absorbing plates is gradually increased in the direction from the end of the main electrode to the mirror, and the vibration wave having a low frequency is set according to the interval. The vibration absorbing plate may be gradually absorbed, but the vibration absorbing plate may be configured to gradually absorb a vibration of a high frequency by providing the intervals of the plurality of vibration absorbing plates gradually narrower. Even if it is provided in only one of the two space portions between both ends and the mirror, the vibration wave can be considerably attenuated.

Spaces provided between the vibration absorbing plates are also provided.
The spacer is made of a vibration absorbing material, and the spacer can absorb the vibration wave. However, even if only the vibration absorbing plate is used without the spacer, the vibration wave can be sufficiently absorbed. .

[0029]

As described above, according to the present invention, at least between the one end of the main electrode disposed in the optical resonator and the output mirror or between the other end of the main electrode and the high reflection mirror. A plurality of vibration absorbing plates are arranged in one space portion while gradually changing the intervals along the optical axis direction.

Therefore, the vibration wave generated in the optical axis direction of the optical resonator due to the main discharge can be attenuated by the vibration absorbing plate, and the distance between the vibration absorbing plates is set in the mirror direction from the end of the main electrode. Since the vibration wave is gradually changed as it goes, the vibration wave in a wide frequency band can be attenuated by the change of the interval.

[Brief description of drawings]

FIG. 1 is a side view showing the overall configuration of an embodiment of the present invention.

FIG. 2 is a sectional view taken along line AA of FIG.

FIG. 3 is an enlarged view of a tube body also provided at the end of the laser tube.

FIG. 4 is a front view of the vibration absorbing plate.

FIG. 5 is an explanatory diagram showing a frequency band of a vibration wave generated by a main discharge.

FIG. 6 is a graph showing the relationship between the magnitude of an oscillating wave and the repetition rate of pulse oscillation in the gas laser device according to the present invention and the related art.

FIG. 7 shows a laser in the present invention and a conventional gas laser device.
The graph of the relation between the output and the repetition rate of pulse oscillation.

[Explanation of symbols]

2 ... Cathode, 3 ... Anode, 14 ... Output mirror, 15 ... High reflection mirror, 17 ... Vibration absorbing plate.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification code Office reference number FI technical display location 7454-4M H01S 3/097 Z

Claims (1)

[Claims] 1. An optical resonator in which an output mirror and a high-reflection mirror are arranged to face each other, and a cathode and an anode arranged in the optical resonator so as to be separated from each other in a direction intersecting the optical axis direction. In the optical axis direction in the space between at least one of the main electrode and the output mirror of the main electrode in the optical resonator, or between the other end of the main electrode and the high-reflection mirror. And a plurality of vibration absorbing plates arranged so as to gradually change intervals along the gas laser device.