JPS60178681A - Gas laser device - Google Patents

Abstract

PURPOSE:To obtain the titled device which can obtain stable and homogeneous discharge by the removal of an electrode from inside a high speed flow of gas in a discharge tube by applying a discharge generating by impressing an AC voltage on a plurality of electrodes provided in opposition to each other in the outer periphery of the discharge tube. CONSTITUTION:The discharge tube 110 of a laser oscillator is filled with a laser medium gas with the mixture of CO2, N2, He, etc. under a pressure of about 100Torr. When a high frequency voltage with a frequency of e.g. about 100kHz and a zero peak of about 5kV is impressed on each metallic electrode 111 and 121 from a high frequency power source 150, AC discharge, i.e. noiseless discharge 130 generates via dielectric, and CO2 molecules are excited. The CO2 molecules excited by this noiseless discharge cause laser oscillation in a photo resonator consisting of a total reflection mirror 4 and a partial reflection mirror 5, and the laser beam is partly taken out of the reflection mirror 5. Then, the laser medium gas is cooled by a heat exchanger 3 and then circulates through the discharge tube 110 at a high speed by a route blower 2. With this CO2 laser device, each metallic electrode 111 and 121 does not exist in the high speed flow of gas, and there is no loss of gas pressure due to these electrodes; accordingly, the discharge becomes stable.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to an improvement in a laser excitation method in a gas laser device.

[Prior art]

Conventionally, a typical gas laser device of this type is shown in FIG. Figure 1 shows conventional DC (direct current)
1 is a schematic configuration diagram showing a glow discharge excited high speed axial flow type COI laser device. In the figure, l is the discharge tube, iiu anode (anode), 12L cathode (cathode), 13 is discharge tube 1
14 is the nozzle, 100 is D
C (DC) power supply, 2 is a roots blower, 3 is a heat exchanger, 4 is a total reflection mirror, 5 is a partial reflection mirror, 6 is a vacuum pump, 7 is a gas recycling device, 8 is a laser gas cylinder,
9 is an air pipe, and 10 is the direction of gas flow.

Next, the operation of the conventional DC glow discharge excited high speed axial flow type CO laser apparatus shown in FIG. 1 will be described. Inside the discharge tube 1 of the laser oscillator, there is CO.

A laser medium gas consisting of a mixed gas of N2, He, etc. is filled at a gas pressure of about several 10 Torr. A DC voltage of approximately several tens of volts is applied between the anode 11 and the cathode 12 to generate a glow discharge 13 within the discharge tube 1 to excite CO7 molecules. Here, the nozzle 14 serves to reduce gas pressure loss and stabilize the glow discharge 13. The COt molecules excited by the glow discharge 13 cause laser oscillation within the optical resonator composed of the total reflection mirror 4 and the partial reflection mirror 5, and a part of the laser beam is emitted from the partial reflection mirror 5 to the outside. It is taken out. In this type of gas laser device, a roots blower 2 normally circulates the laser medium gas within the discharge tube 1 at a high speed of about 200% by about 50 or more to suppress the rise in gas temperature. Moreover, the gas temperature is kept low by the heat exchanger 3. In the gas sealing operation, the anode 11. cathode 1
The gas deteriorates due to ion emission from the metal electrode of the second grade, etc., and the laser output decreases. Therefore, in order to prevent the laser output from decreasing, vacuum pump 6, gas recycling device 7. The purity of the gas is maintained at a substantially constant value by means of a laser gas cylinder 8 or the like, in which a portion of the laser medium gas is flushed away, a portion is regenerated, and a portion is replenished.

The conventional DC glow discharge-excited high-speed axial flow type CO laser device is constructed as described above, so that the anode 11. Due to the presence of metal electrodes such as the cathode 12, there were the following drawbacks.

■ Gas pressure drop increases, gas flow rate decreases and gas temperature increases.

■ Nozzle 14 and each anode 11. The discharge condition is highly dependent on the shape of the metal electrode such as the cathode 12, and variations in the shape have an excessive effect on the laser output and laser beam mode. (For example, published in 1981,
“High-efficiency, high-speed axial-flow CO,” in “Laser Research” Volume 9, No. 1
(Refer to "Laser Development") ■ Each anode 11. Due to ion emission from metal electrodes such as the cathode 12 and abnormal discharge caused by this, gas deterioration is severe and a gas recycling device 7 is required.

In addition, there were various other drawbacks as described below.

(2) A stabilizing effect (by bipolar diffusion) on the wall of the discharge tube 1 is required, and operation with an arbitrary diameter of the discharge tube 1 is impossible.

■ In order to obtain a discharge in the direction 10 of the high-speed gas flow, 1) the inter-electrode distance d between the anode 11 and the cathode 12 becomes long, requiring a high voltage of approximately mtoKv, and 11) the discharge space is The charged region of charged particles flowing in the same direction as the flow direction 10 is very long, and as a result the insulation distance must be long.

■ In order to suppress the rise in gas temperature of the laser medium gas, increasing the gas pressure pfr to increase the mass flow rate is an effective means, and increasing the gas pressure p is also an essential condition for the gas shut-off operation. On the other hand, the value of pd, which is the product of the gas pressure p and the interelectrode distance d, is an indicator of the stability of the discharge, so if the pdO value above exceeds a certain critical value, the discharge becomes unstable. Therefore, as mentioned in (■) above, when the distance d between the electrodes becomes large, it is impossible to increase the gas pressure p beyond a certain level.
It can only be used in areas below Torr.

(2) Since glow discharge 13 may shift to arc discharge due to the influence of residual charge, in pulse discharge, the pulse period cannot be made shorter than the gas discharge section passage time.

[Summary of the invention]

This invention was made with the aim of alleviating all the drawbacks of the conventional ones as described above.The discharge to excite the laser is generated by applying an alternating current voltage to a plurality of opposing electrodes around the outer periphery of the discharge tube. The present invention provides a gas laser device in which an electrode can be removed from a high-speed gas flow in a discharge tube and a stable and homogeneous discharge can be obtained by applying a discharge (silent discharge).

[Embodiments of the invention]

Embodiments of the present invention will be described below with reference to the drawings.

Figures 2 (JL) and (b) are a schematic configuration diagram showing a silent discharge type high-speed axial flow type CO and laser device, which is an embodiment of the present invention, and a cross-sectional view taken along the line A-A. The same parts as in FIG. 1 are indicated using the same reference numerals, and detailed explanation thereof will be omitted. In each of the above figures, 110 is a discharge tube made of a dielectric material such as glass 2 ceramic or titanium oxide;
, 121 is a plurality of metal electrodes provided around the outer circumference of the discharge tube 110, 150 is a high frequency power source connected to each metal electrode 111, 121, 130 is a silent discharge generated inside the discharge tube 110, 140 is a diffuser nozzle It is.

Next, the operation of the silent a-type high-speed axial flow type CO2 laser device, which is an embodiment of the present invention shown in FIG. 2, will be described. Inside the discharge tube 110 of the laser oscillator, COI, N
2. ■The laser medium gas consisting of a mixed gas such as Ie is approximately I
It is filled with a gas pressure of QOTorr. From the high frequency power supply 150, a high frequency voltage with a frequency of about 100 KHz and a zero peak of about 5 V is applied to each gold 11t'I pole 1.
11 and 121, inside the discharge tube 110,
An alternating current discharge, a so-called silent discharge 130, is generated through the dielectric, and CO molecules are excited. The COt molecules excited by the silent discharge 130 cause laser oscillation within the optical resonator composed of the total reflection mirror 4 and the partial reflection mirror 5, and a part of the laser light is transmitted from the partial reflection mirror 5 to the outside. It is taken out.

The laser medium gas is cooled by the heat exchanger 3 and circulated within the discharge tube 110 at high speed by the Roots blower 2. Here, in order to reduce the gas pressure loss of the laser medium gas at the diffuser nozzle 140 forming the expanded flow path St in the discharge tube 110, the diffuser nozzle 140 is configured to have a divergence angle of about 20 degrees.

As described above, according to the silent number turtle type high-speed axial flow type CO laser device which is an embodiment of the present invention, the metal electrodes 111 and 121 do not exist in the high-speed gas flow.
It has various features as shown below.

(2) There is no gas pressure loss due to the metal electrodes 111 and 121 K, and the gas flow rate can be easily increased.

■ Defacer nozzle 14o, each metal electrode 111°1
There is no change in discharge due to the shape of 21, and the discharge is stable.

(2) Gas deterioration due to ion release from each of the metal electrodes 111 and 121 is almost the same as #1, and a gas regeneration device such as a vacuum pump 61 or gas recycling device 7 as shown in FIG. 1 is not required.

■ The stability of the discharge is not only due to the effect of increasing the high-speed gas flow rate described in (■) above, but also due to the capacitive ballast of the dielectric material constituting the discharge tube 110.
effectK further stabilizes the discharge tube 110 and allows operation with any diameter of the discharge tube 110. In other words, even if discharge concentration occurs locally in a part of the discharge space within the discharge tube 10, the discharge concentration is immediately automatically prevented by the reverse electric field pressure of the accumulated charge on the dielectric surface, and as a result, the discharge space becomes homogeneous, and the transition from glow discharge 13 to arc discharge hardly occurs.

■ Since the discharge is in the direction perpendicular to the gas flow, 1) the distance d between the metal electrodes 111 and 121 is shortened, and a relatively low AC voltage of about 5 V is sufficient for the applied voltage; D, II) Also, in AC discharge, the discharge direction and the gas flow direction are perpendicular to each other, so the charging distance on the downstream side of the gas is small. As a result of the above l) and ii), the insulation distance can be shortened. Can be designed.

■ As mentioned in (■) above, since the distance d between the electrodes is small, it is possible to increase the gas pressure pt from the viewpoint of the pdO value, which is the product of the gas pressure p, and it is also possible to increase the mass flow rate. , and the gas sealing operation can be easily performed.

■ Capacitive ball mentioned in ■ above
Ast effecl; allows the pulse frequency in pulse discharge to be increased to the physical limit of the laser medium gas, that is, the relaxation time of the upper level of the laser, without being affected by residual charges.

Note that in the above embodiment, Go2. Although the case of a CO laser device using a laser medium gasket consisting of a mixed gas such as N, , He, etc. has been described, other gas laser devices may be used, and the same effects as in the above embodiments can be obtained. play.

〔Effect of the invention〕

As explained above, this invention provides a laser f of a gas laser device.
The electrodes are removed from the high-speed gas flow inside the discharge tube by applying a discharge (silent discharge) that is generated by applying an alternating current voltage to multiple electrodes placed facing each other around the outer periphery of the discharge tube. However, since it was configured to shorten the distance between the electrodes,
1) Gas flow rate can be easily increased and gas temperature rise can be suppressed 11) Gas sealing operation becomes possible, eliminating the need for gas regeneration equipment such as gas recycling equipment 111)
The insulation distance can be shortened and the entire device can be made more compact.
V) Excellent fc effects such as good stability of emission 1C and an extremely reliable gas laser device can be obtained.

[Brief explanation of drawings]

Fig. 1 is a schematic configuration diagram showing a conventional DC glow discharge excited high speed axial flow type C02 laser device.
is a silent discharge type high speed axial flow type C which is an embodiment of the present invention.
FIG. 2 is a schematic configuration diagram showing a laser device and a cross-sectional view taken along line A-A thereof. In the figure, 1, 11.0 discharge tube, 2... roots blower (blower), 3... heat exchanger, 4-- total reflection mirror, 5-- partial reflection m, 6- * empty pump, 7-・・Gas recycle device L8・Laser gas cylinder, 9・Air pipe, 10- Direction of gas flow, 11・Anode (anode)
, 12. Cathode, 13. Glow discharge, 14
Nozzle, 100, DC (direct current) lightning, source, 111
, 121 metal electrode, 130... silent discharge, ] 40 di7 usa nosuru, 150 high frequency power source. In each figure, the same reference numerals indicate the same or equivalent parts. Agent Masuo Oiwa Figure 1

Claims (1)

[Claims] A laser medium gas is flowed at high speed in the axial direction of the discharge tube into a discharge tube made of a dielectric material, and an alternating current voltage is applied to a plurality of opposing electrodes around the outer periphery of the discharge tube to generate a discharge (silent discharge). What is claimed is: 1. A gas laser device characterized in that the gas laser device is configured to generate a laser beam and oscillate a laser beam by the discharge.