JPS6060793A - Gas laser device - Google Patents

Abstract

PURPOSE:To satisfy the stability of discharge as well as the oscillation efficiency by operating the device with adjusting the ultimate dew point in gas laser to be -30--70 deg.C. CONSTITUTION:In the device which performs a discharge excitation in the laser gas including CO2, the operation is done with keeping the ultimate dew point in the laser gas -30--70 deg.C. For keeping the ultimate dew point within the range of -30--70 deg.C, the water adsorption agent adjusted so as to make the ultimate point -70 deg.C, e.g. molecular shieves 3A is enclosed in the laser gas similarly to the conventional art. Consequently, the laser oscillation efficiency is optimized and the high-reliability discharge can be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a Kaslas laser device, and particularly to the dew point reached by the laser gas.

[Prior art]

A typical gas laser device is a three-axis orthogonal CO2 laser in which the laser source axis, DC glow discharge path, and gas flow are substantially perpendicular to each other, so a conventional example of this will be explained. FIG. 1 is a configuration diagram of a three-axis orthogonal gas laser device, FIG. 1a is a vertical cross-sectional configuration diagram, and FIG.
I1) l-1: A sectional view taken along the line T-■ in FIG. 1a. In the figure (11 is the anode.

(2) is a cathode, (31 is a cathode substrate, (4) is a stabilizing resistor, (5) is a DC high voltage power supply, (6) is a discharge excitation part, (7
) is a total reflection mirror.

(8) is a partial reflection mirror, (9) is a laser beam, 0α blower or heat exchanger, a)) is a gas flow, and 03 is a housing of a gas laser oscillator.

Next, the operation will be explained. The Mononoke anode shown in Figure 1 (
Between 1) and the cathode (2), there is usually co2, N2,
This is a so-called gas-sealing type in which the laser gas consisting of a mixture of Hθ is flowed in the direction of the arrow (111 times) at a flow rate of several tens of meters per second and recirculated. When a voltage is applied, a gentle discharge called a glow discharge occurs between the electrodes, creating a discharge excitation region (6).In this discharge excitation region (6), a population inversion occurs between specific vibrational levels of 002 molecules in the laser gas. occurs.

A resonant system, that is, a total reflection mirror (7) is installed between the discharge excitation part (6)
) and a partial reflector (8) having an appropriate reflectance and power is distributed between them, laser oscillation occurs and the partial reflector (8)
A laser beam (9) with a wavelength of approximately 10.6μ is emitted from the laser beam. Although the laser output increases with increasing discharge power.

For example, if the number of pins of the cathode (2) in FIG. 1 is constant at 7, an increase in the discharge power by one pin, that is, an increase in the discharge current, is equivalent to an increase in the discharge density. From the point of view of making the laser device more compact and cost-reducing, it is sufficient to increase the discharge density Z, but if the current exceeds a certain level, the glow discharge shifts to the arc discharge. Glow discharge is a discharge where only the electron temperature is high, and it is a discharge that can be excited by laser, but when it transitions to arc discharge, the molecular temperature also increases, and laser excitation is no longer performed, and laser oscillation stops in this state. Go down.

Therefore, laser devices are designed to operate at currents before arcing occurs.

On the other hand, the oscillation efficiency of the laser (laser output relative to the discharge power) is basically determined by the formation of the laser gas once the discharge conditions and the configuration of the laser device are determined.

For example, Fig. 2 is an explanatory diagram showing the role of the ao2o laser gas. The CO2 laser gas is a mixture of co2, N2, and He. Upper level (001) and lower level (10
0), and N2 is c
It plays a role in energy transfer to the (001) upper level of o2. Heke co2 is from (ool) level to ([110
) level to the ground state, Z plays a role in promoting the relaxation from the 01 level to the ground state, and as a result keeps the inversion molecular density between the 106μ bands high, which increases the laser oscillation efficiency. Therefore, a mixture of appropriate amounts of stiff gases is usually used as a laser gas to optimize the efficiency of laser oscillation.

Incidentally, in addition to these gases, the influence of water vapor H20 on laser oscillation has also been investigated.

It is known that N20 gas promotes relaxation of CO2 from the (010) level to the ground state. Taking advantage of this effect, there is an example in which a mixed gas of 002 r N2 + N20 is used as a laser gas by using N20'> instead of the expensive He gas.

Figure 3 is a N20 concentration curve diagram disclosed in Patent Application Publication No. 1986-24586.
In addition to Y, the optimal concentration Z for laser oscillation efficiency is shown, and it is shown that the N20 concentration is 10 to 15%. However, as shown in Figure 2, N20 directly relaxes the upper level (001) of CO2 to the ground state, and has the negative effect of lowering the density of inverted molecules in the 10.6μ band, so originally co2'% = (
010) When there is a relatively large amount of He that effectively relaxes the level from the ground state to the ground state, 9, that is, co2 −N2,
When N20Y is added to the He mixed gas, the above-mentioned negative effects become dominant, resulting in a decrease in laser oscillation efficiency. Therefore, in the case of a mixed gas of CO2, N2, and He, conventionally, a moisture adsorbent such as Molecular Sieves 3A is sealed in the laser gas in the laser housing 02 to increase the concentration of N20, but the dew point reached by the laser gas is There has been no quantitative theoretical or experimental study that suggests that the following should be true.

In the past, it has also been clarified that there is a relationship between glow-arc transition current (or power) and water concentration.
The design specifications of the laser oscillator were unclear.

[Summary of the invention]

This invention was developed in view of the above point w6, and the gasley valve is operated by adjusting the reached dew point from 130°C to 170°C.

The aim is to optimize laser oscillation efficiency and provide a gas laser device that can provide highly reliable discharge.

[Embodiments of the invention]

This invention will be explained in detail below.

First, we will show the results obtained through experiments on the influence of moisture on discharge and laser oscillation efficiency. The experiment was conducted using a laser oscillator Z having the structure shown in Fig. 1, and the composition of the laser gas was 002 -00-.
N2-He=2-1-6-3 2, gas pressure 60~
It is performed at 1 2 0 T'orr. In the case of this experiment, the difference from the previous mixing example is that CO is mixed in, but Co increases the equilibrium concentration of CO2 when CO2 dissociates into CO and 02, making gas sealing possible. At the beginning of discharge, the laser oscillation characteristics and the influence of H2O are the same as those of a mixed gas of CO2, 1q2, and He.

Figure 4 shows the relationship between water concentration (=achieved dew point) and discharge.
In the curve diagram, the vertical axis -Tmax in Figure 1 is the current (maximum discharge current) just before the transition from glow to arc discharge.As shown in the diagram, the dew point (moisture limit) is -70℃ (2.6ppm)
Below, ImaX decreases rapidly. In other words, if molecular sieves for moisture adsorption were simply sealed in the laser scum inside the oscillator housing as in the past, the dew point would be 18.
Since the temperature can drop below 0°C, the maX value may drop significantly, resulting in unreliability.
When designing a conventional laser oscillator, K set its maximum rated current (stable glow discharge) at -80 degrees Celsius (8 degrees Celsius).

However, from the standpoint of designing a compact laser oscillator, the moisture content 1&'a' is
It can be seen that it is preferable to increase the power max '12r (increase the discharge power).

FIG. 5 is a curve diagram showing the relationship between laser oscillation efficiency and water concentration. As described above, when a relatively large amount of Hθ is mixed in the laser gas, an increase in water concentration has a negative effect on laser oscillation. Figure 5 shows the influence of C, and when the dew point (moisture content) exceeds -30°C (37 sppm), the laser oscillation efficiency decreases rapidly, but below this concentration, it remains almost constant. .

Based on the results of a series of experiments focusing on moisture.

From the standpoint of discharge, the dew point (moisture 9 degrees) is -70°C (2, s
ppm) or above, and from the standpoint of laser oscillation, from the viewpoint of oscillation efficiency, it should be -30°C (375p1)m.
) It was clarified that the following should be done. Is this the dew point reached by the laser scum of the laser oscillator? Maintaining the temperature within the range of -70°C to -30°C satisfies both the requirements of making the laser oscillator more compact (lower cost) and optimizing the laser oscillation efficiency.

As a method to maintain the ultimate dew point in the range of -10°C to -30°C, use moisture adsorbent 1 adjusted so that the ultimate dew point is -110°C.
For example, it is sealed in a Molecular Laves 3At laser gas as in the conventional case. In other words, the characteristics of molecular sieves are shown in Figure 6, and Figure 6 is a curve diagram showing the relationship between the moisture content of molecular sieves (expressed as wt % of water adsorption amount per unit weight) and adsorbent temperature. When a moisture adsorbent is new, its moisture content is 0 to 1 wt%.

At this time, when the conventional adsorbent installation location temperature, that is, the adsorbent temperature, is 0 to 20°C, the dew point reached by the laser gas is -80°C.
It can be seen that the temperature can exceed ℃. Therefore, the dew point reached -7
In order to achieve a temperature of 0°C (2.5 ppm) or higher, the dew point (water concentration) reached at the location where the moisture adsorbent is installed must be -70°C.
A moisture adsorbent that has previously adsorbed (contains water) an amount of moisture above .degree. C. may be sealed in the laser gas in the laser oscillator. For example, at an adsorbent temperature of 20°C, a moisture adsorbent containing 4.2 wt% moisture will reach a dew point of -70°C (2.5 wt%).
I) pm) or less.

As described above, the dew point of the laser scum can be adjusted to 170° C. (2,000 ppm) or higher by a very simple method in which several percent of water is adsorbed in advance on a conventionally used moisture adsorbent. As shown in Figure 6, the dew point reached by the moisture adsorbent becomes worse as it contains more water.
When the water concentration is higher than -30°C, replace it.

In this way, by maintaining the ultimate dew point within the range of -70°C to -30°C, the first-order effect can also be obtained.

For example, in the case of a DC glow discharge method, the discharge electrode for laser excitation is oxidized due to the reaction with 02 generated by discharge dissociation of CO2 in the CO2 laser gas. The discharge becomes unstable due to the accumulation of oxides (insulators) on the surface.

The current flow rate 1naX decreases as the glow transitions to arc. However, if moisture is present in the discharge field, H2 and OH are generated by the discharge, so the electrode always receives the reduction action, and oxidation of the electrode is not promoted, which has the advantage that the discharge is always stable. on the other hand.

When the water concentration increases, corrosion of metal parts other than the discharge part occurs, so keeping the water concentration of the laser scum within the above range has the effect of preventing deterioration of the discharge electrode and rusting of the structures inside the laser oscillator. Therefore, even in the case of a silent discharge excitation method that occurs when a high AC voltage is applied to a dielectric electrode in a method that does not use metal electrodes, the effect is tremendous.

In the above example, Molecular Reves 3A was used, but other moisture adsorbents may also be used.

Needless to say, the temperature should be adjusted so that the dew point reached is 170°C.

In addition, in the above embodiment, the DC discharge between metal electrodes has been described, but it is also possible to apply an AC voltage between the metal electrodes via the dielectric Z to generate a silent discharge and use this as an excitation discharge. has the same effect.

〔Effect of the invention〕

As stated above, according to the present invention, the operation is adjusted so that the dew point reached in the laser gas is from 130°C to 170°C, thereby satisfying discharge stability and oscillation efficiency at the same time. This has the effect of making it possible to optimally design a reliable laser device.

[Brief explanation of the drawing]

FIG. 1 is a configuration diagram of a three-axis orthogonal gas laser device. Figure 2 is an explanatory diagram showing the role of co2o-laser gas,
Figure 3 shows the relationship between H20 concentration and laser oscillation efficiency. Figure 4 shows the relationship between water concentration and discharge. Figure 5 shows the relationship between laser oscillation efficiency and water concentration. FIG. 6 is a curve diagram showing the relationship between the moisture content of molecular sieves and the temperature of the adsorbent. Agent Masu Oiwa Figure 1 Figure 2 Cθ2 /J2 Figure 3 H2O5i □ degree [〃] Figure 4 Figure 5 Kazutake's traces (rp) Part 6 Senkou system ['C] ]

Claims (1)

[Claims] (It C!O,, y, - In a device that performs discharge excitation in a laser gas containing
A gas laser device that operates while maintaining the temperature between 0°C and -10°C. (2) A gas laser equipment characterized in that a moisture adsorbent adjusted to reach a dew point of 170° C. is sealed in the laser gas.