JPH06291397A - Gas laser oscillation equipment - Google Patents

Abstract

PURPOSE:To increase the oscillation efficiency and the output power of a laser, in a microwave pumping type gas laser oscillation equipment. CONSTITUTION:Microwaves are supplied from magnetrons 13 to a discharge part 15, and a laser beam is obtained from an optical resonator by exciting laser gas in a discharge part 15. The magnetrons 13 supply the microwaves by a microwave power supply 25. The microwave power supply 25 is intermittently operated by a driving signal from a control part 26, and the frequency of the driving signal is set to be 20KHz or higher.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a gas laser oscillator for obtaining a laser beam by exciting a laser gas with microwaves.

[0002]

2. Description of the Related Art As an example of a gas laser oscillator for exciting a laser gas with microwaves, an APPLIED PH
YSICS LETTER, 37 [8] (1980)
P. There is a configuration shown in 673. The above configuration will be described with reference to FIG.

In FIG. 5, reference numeral 1 is a laser tube, and an inlet 3 for injecting a laser gas 2 is formed in an upper portion of the laser tube 1. A waveguide 5 for supplying the microwave 4 into the laser tube 1 is attached to one end of the laser tube 1, and the waveguide 5 and the laser tube 1 are separated by a pressure partition wall 6 attached to the end of the waveguide 5. It is partitioned. The high-pressure laser gas 2 supplied from the inlet 3 of the laser tube 1 has its flow velocity increased by a nozzle portion 7 formed in the middle of the laser tube 1, and is discharged in the direction of arrow 8 by a vacuum pump. Reference numeral 9 is an optical resonator arranged downstream of the nozzle portion 7.

Next, the operation of the gas laser oscillator constructed as above will be described. First, laser gas 2
Is supplied at high pressure into the laser tube 1 through the inlet 3 and passes through the nozzle portion 3 from the non-discharge space 11. Since the laser gas 2 passes through the nozzle portion 7 and adiabatically expands, the gas pressure in the discharge portion 11 downstream of the nozzle portion 7 becomes low and the gas velocity becomes high. The microwave 4 is supplied into the laser tube 1 through a pressure partition wall 19 that transmits the microwave. Since the discharge-free space 10 in the laser tube 1 has a high pressure, no discharge is generated here, and a discharge is generated in the discharge part 11 having a low gas pressure.
The laser output is extracted by the electrostatic charge of the laser gas excited by the microwave by the optical resonator 9 arranged on the downstream side of the discharge section 11. The exhaust gas is exhausted in the direction of arrow 8 by a vacuum pump.

As described above, it is highly expected to extract the laser beam by microwaves from the viewpoint of the cost of the power supply device, but in reality, the microwave-excited gas laser oscillator device for general industrial use is practically used. It has not been converted.

FIG. 6 shows a schematic diagram of the configuration of a microwave-excited carbon dioxide gas laser oscillation device which we have studied based on the above-mentioned gas laser oscillation device.

In the figure, 12 is a discharge tube formed of a dielectric material such as glass, 13 is a magnetron which is a microwave generator for generating microwaves, and 14 is the microwave of the magnetron 13 supplied into the discharge tube 12. It is a waveguide. Since the discharge tube 12 penetrates the waveguide 14, it is excited by the laser gas gas microwave in the discharge tube 12. The part where this laser gas is excited is the discharge part 15. A total reflection mirror 16 is arranged at the end of the discharge tube 12 and a partial reflection mirror 17 is arranged at the other end to form an optical resonator. Partial mirror 1
A laser beam 18 is emitted from 7. An air supply pipe 19 is connected to both ends of the discharge tube 12, and an intake pipe 0 is connected to the central portion of the discharge tube 1. Heat exchangers 21, 22 and a blower 23 are connected between the intake pipe 20 and the air supply pipe 19 to circulate the laser gas. The heat exchangers 21 and 22 are provided to discharge the discharge part 15 and cool the laser gas whose temperature has been raised by the blower 23. An arrow 24 indicates the direction in which the laser gas flows, and the laser gas circulates in the gas laser oscillator shown in the figure.

The operation of the carbon dioxide gas laser oscillating device constructed as above will be described. First, a microwave is applied from the magnetron 13 to the discharge part 15 in the discharge tube 12 through the waveguide 14 to generate glow discharge in the discharge part 15. Since the magnetron 13 operates continuously, the microwave output shown in FIG. 7 is obtained. The laser gas passing through the discharge section 15 is excited by obtaining this discharge energy, and the excited laser gas is reflected by the total reflection mirror 16 and the partial reflection mirror 1.
The optical resonator formed by 7 is brought into a resonance state, and the laser beam 18 is emitted through the partial reflection mirror 17.

[0009]

However, in the method studied by us, as shown in FIG. 8, the laser output A decreases when the microwave injection power exceeds 400 w, and the laser oscillation efficiency B reaches 5 at maximum. %, Which was remarkably low, and when the microwave injection power exceeded 400 w, it remarkably decreased. The microwave injection power is the power injected from the magnetron into the discharge tube, and can be varied by varying the voltage applied to the magnetron.

Consider the above reason. Experiments will be performed by changing the above device to a high-frequency magnetic field application system instead of the microwave excitation system. Specifically, the basic configuration of the device is the same,
When a high frequency magnetic field is applied with a high frequency power source of 13.56 MHz and the characteristics of the laser output are measured, it becomes as shown in FIG. That is, the oscillation efficiency B is 16 when the injection power exceeds 400w.
%, The laser output A increases linearly, and an output of 160 w is obtained with an injection power of 1 Kw. The characteristics deteriorate when the micro-excitation wave discharge is used as described above, and the cause will be described below. In high-frequency discharge, it is known that the so-called skin effect in which the spatial volume of the discharge becomes narrower as the frequency becomes higher, but the microwave from the magnetron is 2.45 GHz and 200 times the frequency as compared to 13.56 MHz. Therefore, it can be inferred that the skin effect occurs. In particular, it is considered that the skin effect becomes remarkable when the injection power increases, and as described above, the laser output may decrease even if the injection power increases.

As described above, the microwave excitation type gas laser oscillator has a problem in that the oscillation efficiency is lowered and the laser output does not increase even if the injection power is increased.

The present invention has been made to solve the above problems, and an object of the present invention is to provide a microwave excitation type gas laser oscillator having high oscillation efficiency and large laser output. .

[0013]

In order to achieve the above object, the present invention provides a microwave generator for generating a microwave, and the microwave from the microwave generator is supplied to a laser gas to excite the laser gas. The discharge unit, an optical resonator that resonates the laser gas excited in the discharge unit to generate a laser beam, and a control unit that controls the operation of the microwave generator, the control unit including the microwave generation unit. Outputs a drive signal for intermittent operation of the device,
The frequency of this drive signal is set to 20 KHz or higher.

[0014]

According to the above construction, since the microwave is intermittently supplied to the discharge part, it is possible to stop the microwave supply from the start of supplying the microwave until the skin effect is confirmed. By repeatedly supplying and stopping microwaves in this way, a uniform discharge can be obtained without the skin effect. Further, since the microwave is intermittently supplied, the laser beam vibrates, but since the drive signal is 20 KHz, the vibration can be reduced.

[0015]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. In FIG. 1, the same components as those in FIG. 6 are designated by the same reference numerals and the description thereof will be omitted.

In FIG. 1, 25 is a microwave power source,
Electric power is supplied to the magnetron 13 which is a microwave generator. Reference numeral 26 controls the operation of the microwave power supply 25 and supplies a drive signal for intermittently operating the magnetron 13. The signal for driving the magnetron 13 is a pulsed signal, and its frequency is set to 20 KHz or more.

In FIG. 2A, the injection power is constant, the frequency of the drive signal is variable, and the output of the magnetron is continuous (c).
The relationship between the magnetron output pulse frequency and the oscillation efficiency when the frequency is changed in a pulse form from w) is shown.
(B) is a diagram showing a microwave output when the magnetron output pulse frequency is zero, and (C) is a diagram showing a microwave output when the magnetron output pulse frequency is 20 KHz.

As is apparent from FIG. 2, if the same frequency of the drive signal is increased and the same frequency of the magnetron output pulse is increased, the oscillation efficiency is improved. It was also found that the higher the magnetron output frequency, the higher the oscillation efficiency. In particular, the relationship between the microwave injection power, the laser output, and the oscillation efficiency when the magnetron output pulse frequency is 15 KHz is shown. The oscillation efficiency B is 16% at maximum and 15% when the microwave injection power is 1 Kw. Further, the laser output A was remarkably improved to 150 w when the microwave injection power was 1 Kw.
As a method of varying the microwave injection power, there is a method of varying the ratio of the ON period and the OFF period of the drive signal. In this case, the ON and OFF periods can be varied even if the same wave number is fixed.

The reason for the above improvement will be devised. First, the discharge behavior under microwave is transiently devised. Initially, the discharge spreads uniformly, and after a certain period of time, the discharge is pinched and confirmed as a skin effect. If microwaves are continuously supplied as in the conventional case, the discharge will first spread, but after a short time, the discharge space will be narrowed due to the skin effect. Therefore, it can be inferred that a uniform discharge was continuously obtained by supplying the pulsed microwave so that the supply of the microwave was stopped earlier than the discharge was pinched.

Further, it has been found that the time stability of the laser output (vibration factor (m)) has a great influence on the cutting surface accuracy, and when the electric power is supplied in pulses, the vibration factor of the laser beam is determined. It is necessary to consider.

FIG. 4A shows the relationship between the measured magnetron output pulse frequency and the laser output oscillation rate,
(B) shows the laser output state when the magnetron output pulse frequency is 3 KHz, (C) shows the laser output state when the magnetron output pulse frequency is 6 KHz, and (D) shows the magnetron output pulse frequency of 20 KHz.
It is a figure which shows the laser output state at the time of. From this figure, it is understood that the oscillation of the laser beam can be suppressed by increasing the magnetron output pulse frequency.
In particular, it was found that the laser beam vibration can be ignored by setting the frequency to 20 KHz or higher.

As described above, according to this embodiment, since the frequency of the signal for driving the microwave power source is pulsed at 20 KHz or higher, the oscillation efficiency can be increased and the laser output can be increased. Further, since it is set to 20 KHz or more, the vibration of the laser output can be ignored.

Although the axial flow type gas laser oscillator is used in this embodiment, the effect can be obtained by using other types of gas laser oscillators.

[0024]

As described above, according to the present invention, since the microwave generator is intermittently operated by the drive signal having the frequency of 20 KHz or more, the oscillation efficiency can be improved and the laser output can be increased.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram of a high-speed axial-flow carbon dioxide laser oscillator according to an embodiment of the present invention.

FIG. 2A is a diagram showing a relationship between a magnetron output pulse frequency and oscillation efficiency. FIG. 2B is a diagram showing a microwave output when the magnetron output pulse frequency is zero. C is a diagram showing a microwave output when the magnetron output pulse frequency is 20 KHz. Figure

FIG. 3 is a diagram showing the relationship between microwave injection power, laser output, and oscillation efficiency when the magnetron output pulse frequency is 15 KHz.

FIG. 4A is a diagram showing a relationship between a magnetron output pulse frequency and laser output oscillation. FIG. 4B is a diagram showing an output behavior when the magnetron output pulse frequency is 3 KHz. FIG. 4C is a diagram showing an output behavior when the magnetron output pulse frequency is 6 KHz. Figure (D) Diagram showing output behavior when magnetron output pulse frequency is 20 KHz

FIG. 5 is a block diagram of a conventional microwave-excited gas laser oscillator.

FIG. 6 is a schematic configuration diagram of a microwave-excited carbon dioxide gas laser oscillation device studied by the inventors.

FIG. 7 is a diagram showing a microwave output state of the gas laser oscillator.

FIG. 8 is a diagram showing the relationship between microwave injection power, laser output, and oscillation efficiency of the gas laser oscillator.

FIG. 9 is a diagram showing the relationship between injection power, laser output, and oscillation efficiency in high-wave discharge at 13.56 MHz.

[Explanation of symbols]

 13 magnetron 15 discharge unit 25 microwave power supply 26 control unit

Claims (1)

[Claims] 1. A microwave generator for generating a microwave, and a discharge unit for exciting the laser gas by supplying the microwave from the microwave generator to the laser gas.
An optical resonator that resonates the laser gas excited in the discharge unit to generate a laser beam, and a control unit that controls the operation of the microwave generation device, the control unit continuously operating the microwave generation device. A gas laser oscillator device which outputs a driving signal to set the frequency of the driving signal to 20 KHz or more.