JPH02133974A - Microwave laser device - Google Patents

Abstract

PURPOSE:To obtain a compact microwave laser device which can cause a uniform glow discharge with normal gas pressure with satisfactory total efficiency by operating a magnetic field at a discharger. CONSTITUTION:A microwave oscillator 11 radiates a microwave 12 to a waveguide 13, a radiated microwave 12 is transmitted to a discharger 7 through a pressure partition wall 14. A permanent magnet 10 is disposed out of the waveguide discharger 7 thereby to form a magnetic field perpendicular to a microwave electric field. Thus, a microwave discharge starting voltage is lowered to maintain a stable glow discharge. Here, an optical resonator 15 composed of a pair of mirrors is disposed out of the discharger 7, when laser gas excited by the microwave is passed through a part having the resonator 15, the laser light is amplified, oscillated to cause an effective laser oscillation. Accordingly, since the energy of the microwave is effectively injected to the discharger 7, a uniform glow discharge is formed, and a microwave laser oscillation having satisfactory total efficiency.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial Application Field) The present invention relates to a high-output, compact 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 a laser medium, and this is particularly important when microwaves are used for discharge excitation. That is,
The pressure used in normal laser oscillation (20
~200 Torr), discharge occurs intensively near the entrance where the microwave enters the discharge section. Therefore, high-density plasma is formed in this portion, and impedance is extremely reduced in this portion. 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.

As a countermeasure against this, for example, literature (Appli, Phys, L
ett, .

37(8), p.673 (1980)), the third
There are things like the one shown in the figure. In FIG. 5, laser gas 31 is supplied at high pressure from an upper inlet 32, and as it passes through a nozzle 33 made of a dielectric material, the gas speed increases and the gas pressure decreases.

On the other hand, the microwave 34 is supplied from the left side in the figure by a waveguide 35 and is supplied to the laser discharge section 41 through a pressure partition wall 36 that transmits the microwave. Since the space 37 of the laser discharge section 41 is under high pressure, no discharge occurs here.As mentioned above, the laser gas is accelerated in the dielectric nozzle 33, and the gas pressure decreases, so that no discharge occurs downstream of the nozzle 33. A microwave discharge 38 is generated. Since the discharge here is a discharge in a low gas pressure, the laser beam passing through the laser gas excited by the microwave is amplified and oscillated by the optical resonator 39 configured on the downstream side. Exhaust gas 4
0 is discharged to the right of the figure by a vacuum pump.

(Problem to be Solved by the Invention) By the way, the biggest drawback of this method is that a vacuum pump is required to exhaust the entire amount of laser gas in order to adiabatically expand it through the nozzle, which requires a large amount of exhaust power for the vacuum pump. This results in an extremely low overall laser oscillation efficiency.

Further, since the gas pressure on the downstream side, that is, the gas pressure in the discharge section is low, it is not possible to obtain a large power density, resulting in a large device, and there are also disadvantages in that a large laser output cannot be obtained.

Therefore, it is not preferable to greatly change the gas pressure, and it has been desired to develop a microwave excitation laser that can operate under the same operating conditions as a normal laser.

An object of the present invention is to provide a compact microwave laser device with good overall efficiency, which is capable of producing a glow discharge of a certain type at normal gas pressures (20 to 200 Torr).

[Structure of the invention]

(Means for Solving the Problems) The microwave laser device of the present invention generates microwave discharge, and furthermore, generates stable microwave discharge by applying a magnetic field to the discharge part, and generates microwaves such as - It causes wave discharge.

Furthermore, by applying a magnetic field in the propagation direction of the microwave electric field, it is possible to stably and uniformly discharge microwaves with high electron density.

(Function) When the microwave power source, which is the main discharge power source, is activated and microwaves are supplied to the discharge section, as mentioned above, the discharge section is an addendum in which the inside of the waveguide is filled with low-pressure laser gas. Due to the action of the waves, -like ionization immediately progresses and the spatial resistance value decreases, making it possible to match the impedance of the incident space, so that the microwave energy is effectively consumed here. Furthermore, a stable and -like glow discharge is formed in the discharge section by the action of the magnetic field in the direction of the electric field, making it possible to optimally excite the laser gas.

Furthermore, if there is a magnetic field in the direction of microwave propagation,
The so-called cutoff frequency of microwaves shifts to the lower frequency side. Therefore, since microwaves can pass through plasma with high electron density, stable uniform discharge is possible.

(Embodiment) An embodiment of the present invention is shown in FIG. 1. In FIG. 1, 1 is a vacuum container, which is evacuated to a vacuum via a valve 3 by an evacuation pump 2. After being evacuated, valve 3
is closed, valve 4 is opened, and laser gas cylinder 5 is opened.
The laser gas is kept at a constant pressure (for example, 5
After the water is injected to 0 Torr, the valve 4 is closed.

As shown by the broken line in Figure 1, this gas supply is normally controlled by a laser gas controller 6 that controls valves 3 and 4, and injection and exhaust are performed alternately or continuously, and the laser gas is constantly replaced in small amounts. It is being A permanent magnet IO is provided outside the waveguide discharge section 1 to stabilize the microwave laser discharge.

A microwave oscillator 11 radiates microwaves 12 into a waveguide 13. The radiated microwave 13 is sent to the discharge section 7 through the pressure partition 14.

The laser gas is circulated by a Roots blower 8 in the direction of an arrow, and the gas leaving the waveguide discharge section 7 becomes high in temperature due to the heating effect of the microwave discharge, so it is cooled by a heat exchanger 9.

A permanent magnet 10 is disposed outside the waveguide discharge section 7, and this creates a magnetic field perpendicular to the microwave electric field, so that the microwave discharge starting voltage increases as shown in FIG. This makes it possible to maintain stable glow discharge.

Furthermore, when a traveling direction magnetic field is present, even more desirable effects can be obtained. In other words, an introductory textbook on plasma physics (
For example, according to "Introduction to Plasma Physics" translated by Uchida, etc.
The plasma frequency ωp is given by ωp=(4πne/m), where the electron mass m, the charge e, and the electron density n. It is known that microwaves with a frequency lower than the plasma frequency ωp cannot propagate in the plasma.

If magnetic field B exists here, using the cyclotron frequency ωC defined by the following equation ωC=e-B/m, the resonance frequency ωh and the two cutoff frequencies ω
R5ωL is given by the following equation.

ωh=vωP+ωC ωR=[ωC+(ωC+4ωP) 1/2ωL=[-ω
C0(ωC+4ωP') l/2 If the phase velocity Vφ for the microwave frequency ω is drawn according to the introductory book mentioned above, the third
Figure shows.

Here, an optical resonator 15 composed of a pair of mirrors is placed outside the waveguide discharge section 7 in FIG. When passing through a certain part of the optical resonator 15, the laser beam is amplified and oscillated. It can be seen that effective laser oscillation is performed in this manner.

To generate a magnetic field, a coil 17 is placed outside the waveguide as shown in FIG. 4(a), and a current is passed through it from the outside to generate a magnetic field in the direction of microwave propagation. Of course, this magnetic field in the direction of microwave propagation can also be achieved by a combination of permanent magnets.

In this way, according to this embodiment, microwave energy is effectively injected into the waveguide discharge section 7.

It can be seen that a glow discharge like - is formed, and effective amplification and oscillation of the laser beam is performed.

Furthermore, when a magnetic field acts in the direction of microwave propagation, the microwaves penetrate deeper into the plasma, resulting in an energy-efficient microwave laser oscillator due to effective excitation.

A second embodiment of the present invention is shown in FIG. 4(b). In Fig. 4(b), a magnetic field in the microwave propagation direction is generated by a permanent magnet, and the effective magnetic field in the propagation direction is generated by the action of the permanent magnet 18 and the ferromagnetic material 19 as shown in Fig. 4(b). occurs. Therefore, the microwave plasma penetrates into the microwave plasma, and a uniform, high-density microwave plasma is generated, resulting in good overall energy efficiency.

〔Effect of the invention〕

As described above, according to the present invention, microwave energy is effectively injected into the discharge section and a --like glow discharge is formed, so that effective amplification and oscillation of laser light is performed, resulting in good overall efficiency. This results in microwave laser oscillation.

Furthermore, a feature of microwaves is that space charges are trapped in the discharge space, so unlike normal DC or AC lasers, there is no need for a cathode fall section to supply electrons.
The efficiency of laser light excitation by discharge is increased.

[Brief explanation of the drawing]

Figure 1 is a sectional view of the microwave laser device of the present invention, Figure 2 is a sectional view of the microwave laser device of the present invention;
Figure 3 is a characteristic diagram showing the effects of the present invention, Figure 4 (a)
, (b) are perspective views showing magnetic field generating devices, and FIG. 5 is a sectional view showing the main parts of a conventional laser device. DESCRIPTION OF SYMBOLS 1... Vacuum container, 2... Vacuum pump 5... Laser gas cylinder 7... Discharge part 8... Roots blower 9... Heat exchanger 10... Permanent magnet 11... Microwave Power source 12...Microwave 13...Waveguide 14...Pressure bulkhead
15... Optical resonator 16... Waveguide
17... Coil for magnetic field generation 18... Permanent magnet for longitudinal magnetic field generation 19... Ferromagnetic agent Patent attorney Nori Chika Ken Yudo Daishimaru Ken Diagram 300 (θ-3) Radial field H No. Figure diagram

Claims (1)

[Claims] A laser medium gas containing CO_2, etc. is sealed in a vacuum container at low gas pressure, and this gas is circulated through a heat exchanger to the waveguide discharge section using a blower, and microwaves are applied to the discharge section from an external microwave power source. In a microwave laser device that excites a laser medium gas by direct glow discharge within a waveguide, a magnetic field is applied from the outside to a waveguide discharge section where laser excitation is performed. microwave laser equipment.