JPH03235386A - Microwave laser - Google Patents

Abstract

PURPOSE:To obtain even flow discharge at a normal gas pressure by a method wherein additional gas injection holes are arranged at a proper interval in the longitudinal direction of a discharge part and additional gas is added in the discharge part through the injection holes. CONSTITUTION:When additional gas, such as Xe gas, Ne gas or the like, is injected in a discharge part 24 through additional gas injection holes 35, which are interconnected to the discharge part 24 and are arranged, an ionization part 35a is formed in the vicinity of each injection hole 35, a remaining part 35b and the like and ionized by electrons, which are fed from the ionization part 35a, and the whole discharge is completed. Accordingly, it is eliminated that microwave discharge concentrates on the vicinity of the entrance of the discharge part 24 and even microwave discharge can be obtained at a normal gas pressure. Moreover, as the ratio of gas, which is added to the feed rate of laser gas, is properly selected, the rate of the Xe gas or the like in the circulating laser medium gas becomes a proper one, an electron density in glow discharge plasma is properly reduced and becomes the optimum one for laser excitation and in addition to these, a discharge impedance is also increased and the constitution of a microwave laser becomes an effective one.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial Application Field) The present invention relates to a microwave laser device that performs microwave discharge excitation.

(Prior art) Generally, in order to obtain laser oscillation, it is necessary to generate a spatially uniform discharge in the laser medium, but this is especially important when microwaves are used for discharge excitation. Become. That is, when microwaves are used at the pressure used in normal laser oscillation (20 to 200 Torr), the discharge starting voltage is much higher than the discharge sustaining voltage, that is, the steady-state operating voltage, so it is not enough to generate a discharge. When high-intensity microwaves enter the discharge section, discharge occurs intensively near the entrance. Therefore, high-density plasma is formed in this portion, and the impedance is extremely reduced. As a result, almost 100% of the incident microwave is reflected as soon as it enters the discharge section, and no electrical input is effectively supplied to the discharge space.

In order to solve these problems, App 1i.

Phys, Let t,, 37 (8), p673 (1
980) proposed a microwave laser device as shown in FIG. That is, in FIG. 4, a laser gas 1 is supplied at a high pressure from an upper part 2 of a discharge section, and as it passes through a nozzle 3 made of a dielectric material, the speed increases and the gas pressure decreases.

On the other hand, microwaves 4 used for discharge excitation are supplied from the left side in the figure by a waveguide 5, and are supplied to the laser discharge section 11 through a pressure partition 6 that transmits microwaves.

Here, in the space of the laser discharge section 11, the space 7 in front of the nozzle 3 has a high pressure, so no discharge occurs in the space 7. On the other hand, since the gas pressure decreases in the space 8 behind the nozzle 3, microwave discharge occurs in this area. The discharge in this part is uniform because it is a discharge in a low gas pressure, and the laser beam passes through the laser gas excited by microwaves by the optical resonator 9 disposed downstream of the laser discharge section 11. is amplified and oscillated. Further, the exhaust gas 10 is discharged to the right in the figure by a vacuum pump.

(Problem 8 to be Solved by the Invention) However, in the conventional microwave laser device having the above configuration, there were problems to be solved as described below.

That is, since the laser gas 1 supplied at high pressure is adiabatically expanded through the nozzle 3 and the gas pressure is lowered, a vacuum pump is required to exhaust the entire amount of the laser gas. Moreover, the exhaust power of the vacuum pump becomes large, leading to an increase in the size of the device, and the overall laser oscillation efficiency is extremely reduced.

Additionally, conventional microwave laser devices have the disadvantage that discharge is concentrated near the exit of the nozzle. In other words, the pressure gradient downstream from the nozzle is lowest at the nozzle exit and gradually increases, and the microwave electric field strength also reaches its maximum near the exit due to the effect of the insulator nozzle, so discharge occurs near the nozzle exit. You will have to concentrate. As a result, the gas temperature at the nozzle exit increases by 1-1, resulting in a decrease in laser excitation efficiency, and the arc limit also decreases, resulting in a decrease in laser output.

Therefore, there has been a strong desire to develop a microwave laser device that improves these drawbacks.

The present invention was proposed in order to eliminate the above-mentioned drawbacks of the prior art, and its purpose is to create a compact, highly efficient overall system that can obtain a uniform glow discharge under normal gas pressure. An object of the present invention is to provide a microwave laser device.

[Structure of the Invention] (Means for Solving the Problems) The present invention is characterized in that a laser medium gas is sealed in a vacuum container at a low gas pressure, the gas is circulated to a discharge part, and the gas is disposed outside the discharge part. In a microwave laser device that excites a laser medium gas by supplying microwaves from a microwave power source, the gas is discharged, and additional gas inlets are disposed at appropriate intervals in the longitudinal direction of the discharge part, The present invention is characterized in that an additive gas having the effect of promoting discharge and lowering the electron temperature is added into the discharge section from the additive gas injection port.

(Function) According to the microwave laser device of the present invention, when the microwave power source is activated and microwaves are supplied to the discharge section, an additive gas such as Xe, Ne, Hg, etc. is injected into the discharge section; For example, the amount of the added gas is adjusted to increase in the direction of the laser gas flow, so that the ignition of the microwave becomes uniform, and since the added gas is mixed with the laser gas in an appropriate amount, the electrons of the microwave discharge are The temperature drops to a suitable value,
This makes it ideal for laser excitation.

(Example) Hereinafter, an example of the present invention will be specifically described based on FIGS. 1 and 2.

In this embodiment, as shown in FIG. 1, the microwave 22 sent out by the microwave oscillator 21 is configured to be radiated into a waveguide 23. Also,
A discharge section 24 made of an insulator with low microwave loss, such as quartz glass, is inserted into the waveguide 23 .

The tip of this discharge section 24 becomes a circulation wind tunnel 26 to constitute a vacuum container 27, and a heat exchanger 28 is installed inside the vacuum container 27.
and a blower 29 are provided. The laser gas is configured to be circulated within the vacuum vessel 27 in the direction of arrow 20 in the figure. Further, the vacuum container 27 includes:
A vacuum pump 30 is connected via an exhaust valve 33, and is configured to evacuate the inside of the container. Further, a laser gas cylinder 31 is connected via a gas supply valve 32, so that the container can be filled with laser gas.

Note that the exhaust valve 33 and the gas supply valve 32 are controlled by a controller 34.
are connected to each other, and their opening and closing are controlled. Further, the discharge section 24 is provided with additive gas inlets 35 at appropriate intervals in the longitudinal direction of the discharge section. A semi-transmissive mirror 36 and a total reflection mirror 37 are disposed on both sides of the discharge section to form a pair of optical resonators, and the glow discharge generated in the discharge section 24 excites the laser beam. 38 and is configured to be taken out to the outside.

In addition, from the additive gas inlet 35 to the discharge section, Xe, N, which has the effect of promoting discharge and lowering the electron temperature.
Gases such as e, Hg, etc. are supplied.

In the microwave laser device of this embodiment having such a configuration, uniform glow discharge can be obtained as described below. That is, inside the vacuum container 27, the exhaust valve 3
3 and is evacuated by a vacuum pump 30. After being evacuated, the exhaust valve 33 is closed, the gas supply valve 32 is opened, and laser gas is injected into the container from the laser gas cylinder 31 to a constant pressure. As shown by the broken line in FIG. 1, this gas supply is normally performed by controlling the exhaust valve 33 and the gas supply valve 32 by a controller 34, so that injection and exhaust are performed alternately or continuously, so that a small amount of laser gas is always supplied. are being exchanged. Further, a discharge section 24 is disposed within the vacuum container 27, and laser gas is circulated by a blower 29. Further, the laser gas that has exited the discharge section 24 has a high temperature due to the heating effect of the microwave discharge, and is therefore cooled by the heat exchanger 28 .

In addition, in the microwave laser device of this embodiment, discharge is generated within the discharge tube made of an insulator, and the discharge portion 2
From the additive gas inlet 35 disposed in communication with
, N6, or the like is injected into the discharge section 24. These additive gases facilitate the generation of discharge and have a remarkable effect of lowering the electron temperature. And the first
In the figure, when microwaves are incident on the discharge part,
Since the microwave electric field strength is close to the sustaining voltage that normally does not cause discharge, it does not normally cause discharge.

However, in this embodiment, since the additive gas such as Xe and Ne is injected into the discharge part 24 from the additive gas inlet 35 provided in the discharge part, the additive gas is injected into the discharge part 24 as shown in FIG. An ionized portion 35a is formed near the injection port 35. The electrons supplied from this ionization part 35a remain in the remaining part 3.
5b etc., and the entire discharge is completed. therefore,
The microwave discharge is no longer concentrated near the entrance of the discharge section, and a negative-like microwave discharge can be obtained. Furthermore, since the ratio of the small amount of gas added to the amount of laser gas supplied is appropriately selected, the ratio of Xe, etc. in the circulating laser medium gas becomes appropriate. As a result, the electron density of the glow discharge plasma is appropriately reduced, making it optimal for laser excitation, and the discharge impedance is also increased, making the overall device configuration more effective and compact.

In this manner, according to this embodiment, microwave energy is effectively injected into the discharge portion, so that various glow discharges can be formed. In addition, the impedance of the discharge plasma becomes appropriate, the configuration including the power supply circuit becomes compact, and the electron temperature can be appropriately lowered, so that a high-efficiency, high-output laser can be obtained.

Note that the present invention is not limited to the embodiments described above, and as shown in FIG. 3, around the microwave discharge section,
A detector 40 capable of grasping the discharge status is provided, and based on information from the detector 40, opening and closing of the additive gas injection port 35 is adjusted to control injection of the additive gas. You may do so. In this case, since the injection amount of the additive gas can be controlled according to the situation inside the discharge section, the discharge becomes uniform and is maintained in an optimal state.

[Effects of the Invention] As described above, according to the present invention, the additive gas inlets are disposed at appropriate intervals in the longitudinal direction of the discharge section, and the discharge is promoted from the additive gas inlets. A compact microwave laser device with good overall efficiency that can obtain a similar glow discharge with normal gas pressure by adding an additive gas that has the effect of lowering the electron temperature into the discharge section. can be provided.

[Brief explanation of drawings]

FIG. 1 is a configuration diagram showing one embodiment of the microwave laser device of the present invention, FIG. 2 is an enlarged sectional view of section A in FIG. 1, and FIG. 3 is a sectional view showing another embodiment of the present invention. FIG. 4 is a sectional view showing the main parts of the conventional example. DESCRIPTION OF SYMBOLS 1... Laser gas, 3... Nozzle, 4... Microwave, 5... Waveguide, 6... Pressure partition, 8... Microwave discharge, 9... Optical resonator, DESCRIPTION OF SYMBOLS 10... Exhaust gas, 11... Laser discharge part, 21-... Microwave oscillator, 22... Microwave, 23... Waveguide, 24
...Discharge part, 26...Circulation wind tunnel, 27...Vacuum container, 28...Heat exchanger, 29...Blower, 30...
・Vacuum pump, 31... Laser gas cylinder, 32
...Gas supply valve, 33...Exhaust valve, 34...Controller, 35...Additional gas inlet, 36...Semi-transmissive mirror, 37...Total reflection mirror 38...Laser light, 4
0...Detector.

Claims (1)

[Claims] A laser medium gas is sealed in a vacuum container at low gas pressure, this gas is circulated to a discharge section, and a microwave is supplied from a microwave power source disposed outside the discharge section to generate a discharge. In a microwave laser device that excites a laser medium gas, additive gas inlets are disposed at appropriate intervals in the longitudinal direction of the discharge section, and the additive gas inlets promote discharge and increase the electron temperature. 1. A microwave laser device characterized by being configured such that an additive gas having an effect of reducing the temperature is added into a discharge section.