JPS6122680A - Mixture gas for carbonic acid gas laser oscilator excited by silent discharge - Google Patents

Abstract

PURPOSE:To obtain a mixture gas which can provide stable performance for a long period of time, by optimizing the composition of a mixture gas containing CO2 used as a laser medium gas in a carbonic acid gas laser oscillator excited by silent discharge. CONSTITUTION:The surface of a metal is covered with an inductor such as glass. A pair of electrodes 1 are provided to be opposed to each other with a proper discharge gap. Silent discharge is caused between these electrodes 2 by applying power from a high-frequency power source 2. A partial reflecting mirror 3 disposed on the laser exciting optical axis, together with a total reflecting mirror 4, provides an optical resonator. In an orthogonal triaxial carbonic acid gas laser oscillator thus provided, the composition of a mixture gas is maintained such that the mole fraction ratio of CO2 to CO is 2:1. That is, when the amounts of CO2 and CO are increased proportionally by a certain value, a maximum pulse laser output waveform is obtained when CO2 is 12% and CO is 6%.

Description

[Detailed Description of the Invention] The invention of C is directed to CO2'? used as a laser medium gas in a silent discharge excited carbon dioxide laser oscillator. The invention relates to mixed gases containing mixed gases, and particularly to improving the composition of mixed gases.

Generally, there is a carbon dioxide laser oscillator of this type as shown in FIG. Fig. 1 is a schematic diagram of an oscillator. In Fig. 1, (1) is a pair of electrodes covered with a dielectric material such as glass on a metal surface and provided facing each other with an appropriate discharge gap;
(2) is a high frequency power source that is applied between the electrodes (1) to generate a silent discharge, (3) is a partial reflection mirror installed on the axis of the laser excitation source, and (4) is a total reflection mirror with one part. Reflector(
3) together form an optical resonator.

The carbon dioxide laser oscillator constructed in this manner is called a three-axis orthogonal type, and its operation will be explained below.

First, a laser medium gasket containing CO2Y7 in the discharge gap.

It is made to flow in the direction of the arrow in the figure under a pressure of about 100 Torr. Further, the gas whose temperature has increased due to the discharge is passed through a cooling device (not shown) F/ such as a heat exchanger, and is circulated to the discharge gap again by a blower (not shown). FIG. 2 shows the voltage waveform of the high frequency power source (2) applied to the pair of electrodes (1). The fundamental frequency of this voltage waveform is 100 to 150 KH.

The voltage value is about 10 KV at the peak value, and as shown in FIG. 2, AM modulation of 0.1 to 2 KH2 is applied. When a discharge is caused between the pair of electrodes (11) using this voltage waveform, the residence time of CO2 gas molecules at the laser excitation level is extremely long (approximately 50 μsec) compared to the excitation time at the discharge fundamental frequency.

The laser output waveform is pulsed as shown in FIG. This laser output is resonated by an optical resonator constituted by a total reflection mirror (4) and a partial reflection mirror (3) provided at both ends on the excitation source axis, and the output wavelength of CO2 from the partial reflection mirror i3) is 1 μm. This will be extracted as a pulsed laser beam. Note that the characteristic diagrams in Figures 2 and 3 show an example of obtaining a pulsed laser beam, but if high-frequency discharge is performed continuously at the fundamental frequency, the laser output will be a continuous wave output called CW. I can do it.

By the way, in the apparatus shown in Fig. 1, Table 1 shows the composition of the most efficient mixed gas for confining the mixed gas containing CO2, which is the laser medium gas, in the excavator and performing continuous CW oscillation for a long time. The effect of mixing C02 with N2 and He gas as a laser medium gas used in a carbon dioxide laser oscillator using the components and composition of (A gas) shown in It is mixed in order to preset the equilibrium condition in which it dissociates due to discharge and becomes OO+O.

When using the conventional mixed gas (A gas), in the region where the laser output is low during OW oscillation, that is, the injection discharge input is low, the temporal change in the laser output for the same discharge input is only after 100 hours have passed after filling the gas. There are also few.

However, when performing continuous pulse oscillation with a high discharge pressure in order to obtain a pulse output waveform with a high peak output, the average laser output is approximately 25 Hr under a constant discharge input condition.
It was later discovered that there was a serious drawback in that it was reduced by half.

This invention was made in order to eliminate the drawbacks of the conventional ones, and it changes the composition of a mixed gas containing 5C02 used as a laser medium gas in a silent discharge-excited carbon dioxide laser oscillator operated in a waste-sealed manner. The aim is to provide a gas mixture that can be optimized and exhibit stable performance over a long period of time.

Hereinafter, one embodiment of the present invention will be described using a three-axis orthogonal silent discharge excited type carbon dioxide laser oscillator.
The composition of the mixed gas was varied under the operating conditions shown below, and the average laser output was measured using a thermocouple calorimeter under a constant discharge input.

Further, experiments were conducted to measure the temporal changes in each pulse output waveform using an Au % Qe element.

As a result of various measurement experiments, FIG. 4 shows the temporal change in laser output, and FIG. 5 shows the pulsed laser output waveform immediately after the start of discharge.

Table 1 shows a comparison between the composition of the conventional mixed gas (A gas) and the composition of the mixed gas (CB gas), which has been revealed by the present invention and enables the most efficient laser oscillation.

As a result of experiments, it became clear that keeping the molar fraction ratio of co2 and CO at about 2 = 1 is better than the dissociation equilibrium condition.
If the amount of o is proportionally increased by a constant amount compared to the conventional one, C! The pulse laser output waveform reaches its maximum at 0212% and 006%.

However, it was observed that it exists. According to (B gas) in Table 1, which is the mixing ratio of one example of the present invention.

When a continuous oscillation test was conducted under the operating conditions shown in Table 2, as shown in Figure 4, the conventional (A gas)
After 5 hours, the discharge input remained constant, but the average laser output was halved, but with (B gas), even after 100 hours of continuous operation, the average laser output was almost the same as at the beginning of operation. No significant change was observed in the waveform caused by the -Ge element.

This invention was made in order to prevent an early drop in laser output due to the short lifetime of the mixed gas and the gas deterioration in a short period of time in conventional systems during pulse oscillation that requires a high peak value. However, from the observation results of the pulse waveform by the Au-Ge element, as shown in Fig. 5, the pulse peak output of the first embodiment of the present invention increases by 20 to 30% compared to the conventional one. The secondary effect is also obtained.

It should be noted that this invention is not limited to (B gas) in Table 1, but it is easily understood that the same effect can be obtained even with 6,000 changes in 4 compositions11. According to what was confirmed through experiments, Table 3 shows the scum composition that can significantly extend the scum life and also increase the peak of the pulse output.

Table 3 As described above, the mixed gas of the present invention can be used.

Not only can a stable laser output be obtained for a long time of 1o-o:Hr or more, but also the laser oscillation efficiency is increased and a high laser output can be obtained.

[Brief explanation of the drawing]

Figure 1 is a schematic diagram of a silent discharge pumped carbon dioxide laser oscillator, Figure 2 is a voltage waveform diagram of a high-frequency discharge source, Figure 3 is a pulsed laser output waveform diagram, and Figure 4 is a conventional mixed laser oscillator. A diagram showing the time change in the average laser output under constant discharge input conditions for gas (A) and the mixed gas (B) of the embodiment of the present invention. Figure 5 shows the variation of the laser average output over time under conditions of constant discharge input with the gas (A) and the mixed gas (B) of the embodiment of the present invention. FIG. 6 is a diagram showing a pulsed laser' output waveform immediately after the start of discharge under a constant discharge input condition using the mixed gas (B) of the example. (11 is an electrode, (2) is a high-frequency discharge source, (3) is a partially reflecting mirror, (41 is a total reflecting mirror)

Claims (4)

[Claims] (1) The opposing direction of the pair of opposing electrodes, the gas flow direction of the laser medium mixed gas flowing between the pair of electrodes, and the partial and total reflecting mirrors facing each other across the discharge gap between the pair of electrodes. The composition of the above-mentioned mixed gas, which is sealed and circulated in a three-axis orthogonal silent discharge pumped carbon dioxide laser oscillator in which the resonator axes of optical resonators each consisting of a reflecting mirror are orthogonal to each other, satisfies the following conditions. A mixed gas for a silent discharge excited carbon dioxide laser oscillator, characterized in that: (2) A mixed gas for a silent discharge excited carbon dioxide laser oscillator according to claim (1), characterized in that the composition of the mixed gas is 1/2 CO_2. (3) A mixed gas for a silent discharge excited carbon dioxide laser oscillator according to claim (2), characterized in that the mixed gas has the following composition. (4) A mixed gas for a silent discharge excited carbon dioxide laser oscillator according to claim (3), characterized in that the carbon dioxide laser oscillator is a pulsed laser oscillator.