JPH0936463A - Microwave gas laser and microwave discharge pumping method therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enhance the laser output and oscillation efficiency by subjecting a laser gas medium to uniform discharge pumping without raising or distributing the gas temperature on the optical axis of laser. SOLUTION: A microwave oscillated from a microwave oscillator 2 is introduced through a waveguide 3 to a rectangular cavity resonator 14 to form a microwave field of TE10 mode having substantially constant strength vertically to the optical axis of laser light. A laser gas medium in a discharge tube 1 is subjected to discharge pumping efficiently by the microwave field to produce a laser output. Furthermore, shift in the resonance frequency of standing microwave caused by the design error of rectangular cavity resonator 14 is corrected by fine adjustment of the insertion length of movable end plates 9a, 9b for wavelength tuning disposed in the rectangular cavity resonator 14.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a microwave discharge excitation method and a microwave gas laser device for a gas laser, which discharge-excites a laser gas medium by electromagnetic waves in the microwave region.

[0002]

2. Description of the Related Art A conventional microwave gas laser device will be described with reference to FIGS. 4 is a front sectional view of a conventional microwave gas laser device, FIG. 5 is a side sectional view of a cylindrical cavity resonator in the microwave gas laser device shown in FIG. 4, and FIG. 6 is a microwave gas laser shown in FIG. It is a schematic diagram which shows the microwave electric field mode in the cylindrical cavity resonator of an apparatus.

As shown in FIGS. 4 and 5, the discharge tube 1 is axially inserted and installed in a cylindrical cavity resonator 4, and a total reflection mirror 5 and an output mirror 6 are provided at both ends thereof. And are installed opposite to each other. The waveguide 3 is provided on the side of the cylindrical cavity resonator 4.
The microwave oscillator 2 is connected via.

Therefore, the microwave output from the microwave oscillator 2 propagates in the waveguide 3 and is transmitted to the cylindrical cavity resonator 4, and the electric field of the microwave causes the discharge tube 1 to be discharged.
The laser gas medium therein is discharge-excited. Thereby, the stimulated emission light from the laser gas medium is obtained, and the stimulated emission light is amplified by the reciprocal reflection between the total reflection mirror 5 and the output mirror 6 forming the optical resonator, and then transmitted through the output mirror 6. The laser light 7 is taken out.

A method of exciting a discharge of a laser gas medium by microwaves is described in Handy and Brandeli.
k, J. et al. Appl. Phys. Vol. 49, p375
3-3756 (1978).

[0006]

However, when the cavity resonator enclosing the microwave is used, it is possible to discharge excite the laser gas medium, but it can be formed in a normal cavity resonator. A TM mode (Transverse Magnetic Mod) is used as a standing wave of the microwave.
e) Or TE mode (Transverse El
A large number of modes co-exist as is known as an electric mode). Therefore, due to load fluctuation due to design error of cavity resonator and generation of discharge plasma in discharge tube,
The resonance frequency of the microwave electric field mode deviates from the initial setting, and as shown in FIG. 6, the electric field vector 8 of the microwave that discharge-excites the laser gas medium becomes complicated and diversified. Therefore, the microwave electric field strength is not constant in the discharge tube axis direction (laser optical axis direction). The discharge plasma generated by such an electric field easily absorbs microwave energy, and the discharge plasma in the laser gas medium flowing in the discharge tube absorbs more microwave energy on the downstream side.

Therefore, in the conventional microwave gas laser device, the laser gas medium cannot be discharge-excited in the entire discharge tube, and the microwave electric field for discharge-exciting the laser gas medium is concentrated in a local space in the discharge tube. Since the temperature of the discharge plasma generated in the above-mentioned rises especially on the downstream side, it becomes difficult to establish the population inversion of the energy level that contributes to the laser oscillation, so that the laser output and the oscillation efficiency decrease. Further, there is a defect that the oscillation gain is reduced on the downstream side in the axial direction of the discharge tube.

Therefore, the present invention has been made in order to solve the above-mentioned disadvantages of the prior art, and the design of the cylindrical cavity resonator is selected from the various microwave electromagnetic field modes used in the cylindrical cavity resonator. T suitable for laser oscillation regardless of whether the load fluctuates due to error or generation of discharge plasma
Microwave of a gas laser capable of improving the laser output and the oscillation efficiency by uniformly exciting the laser gas medium by the electric field of the microwave only in the M ₁₀ mode without causing the temperature rise and distribution of the gas on the laser optical axis. An object of the present invention is to provide a microwave discharge excitation method and a microwave gas laser device.

[0009]

A first gas laser microwave discharge excitation method of the present invention which achieves the above object, comprises:
Microwave of a gas laser that guides microwaves oscillated from a microwave oscillator to a cavity resonator and discharges a laser gas medium in a discharge tube installed in the cavity resonator by a microwave electric field to obtain a laser output. In the wave discharge excitation method, a TE ₁₀ mode microwave electric field is formed inside the cavity resonator, the electric field direction being perpendicular to the optical axis of the laser light and the intensity being substantially constant, and the microwave electric field is used to generate the laser gas. It is characterized in that the medium is discharge-excited.

A second method is the same as the first method, except that the laser gas medium is discharged at a half wavelength of the microwave standing wave formed by the microwave electric field mode of TE _{10 in} the cavity resonator. It is characterized by exciting.

A third method is the rectangular cavity resonator according to the first or second method, wherein the cavity resonator has a predetermined size, and TE _{10 is} provided in the rectangular cavity resonator. A microwave standing wave formed in the rectangular cavity resonator is formed by changing the length of the long side of the rectangular cross section of the rectangular cavity resonator while forming a microwave electric field of the mode. It is characterized in that the effective excitation length of the laser gas medium is controlled by changing the wavelength.

Further, a first microwave gas laser device of the present invention which achieves the above object, comprises a microwave oscillator,
The laser gas medium includes a cavity resonator into which microwaves oscillated from the microwave oscillator are introduced, a discharge tube installed in the cavity resonator, and a laser gas medium in the discharge tube. In a microwave gas laser device for obtaining a laser output by performing discharge excitation by a microwave electric field formed in the cavity resonator, the electric field direction is perpendicular to the optical axis of the laser light inside the cavity resonator. Is provided with a means for forming a TE ₁₀ mode microwave electric field whose intensity is substantially constant.

The second device is the same as the first device, except that the laser gas medium is discharged at a half wavelength of the microwave standing wave formed by the microwave electric field mode of TE _{10 in} the cavity resonator. It is characterized in that a means for exciting is provided.

A third device is the rectangular cavity resonance according to the first or second device, which has a predetermined dimension for forming a TE ₁₀ mode microwave electric field inside the cavity resonator. And the wavelength of the microwave standing wave formed in the rectangular cavity is changed by changing the length of the long side of the rectangular cross section of the rectangular cavity. It is characterized in that a movable end plate for wavelength tuning for controlling an effective excitation length of a gas medium is provided in the rectangular cavity resonator. According to the microwave discharge excitation method of the gas laser and the microwave gas laser device of the present invention,
The laser gas medium in the discharge tube can be efficiently discharge-excited by the TE ₁₀ mode microwave electric field formed in the cavity resonator.

In particular, 1/2 of the microwave standing wave formed in the microwave electromagnetic field mode of TE ₁₀ inside the cavity resonator.
By making the wavelength longer than the discharge length of the laser gas medium, a uniform microwave electric field can be obtained on the laser optical axis, and this electric field causes a uniform discharge in the laser optical axis direction to cause cavity resonance. The laser gas medium in the chamber can be efficiently discharge-excited.

Further, the deviation of the resonance frequency of the microwave standing wave caused by the design error of the cavity resonator and the fluctuation of the load due to the discharge plasma generated inside the cavity resonator causes the deviation of the resonance frequency of the rectangular cavity resonator in the rectangular cross section. Since it can be corrected by changing the length of the long side, it is possible to easily form a uniform microwave electric field in the direction of the laser optical axis in the rectangular cavity, and to generate a uniform discharge in the direction of the laser optical axis. And discharge excitation of the entire laser gas medium becomes possible.

[0017]

BEST MODE FOR CARRYING OUT THE INVENTION An embodiment of the present invention will be described below with reference to FIG.
This will be described in detail with reference to FIGS. 2 and 3.

Here, a case where a rectangular cavity resonator is used as the cavity resonator is illustrated, and FIG. 1 is a front sectional view of a microwave gas laser device including such a rectangular cavity resonator, and FIG. Is a side sectional view of a rectangular cavity resonator in the microwave gas laser device shown in FIG. 1, and FIGS.
FIG. 2 is a schematic view of a microwave electric field mode in the rectangular cavity resonator of the microwave gas laser device shown in FIG. 1. In these figures, the same parts as those in FIGS. 4, 5 and 6 described above are designated by the same reference numerals.

As shown in FIGS. 1 and 2, the discharge tube 1 is disposed inside the rectangular cavity resonator 14 with the laser optical axis sandwiched between the rectangular cavity resonator 14 and the rectangular cavity resonator 14. A total reflection mirror 5 and an output mirror 6 are installed opposite to each other on both ends.
A microwave oscillator 2 is connected to a side portion of the rectangular cavity resonator 14 via a waveguide 3.

Further, as shown in FIG. 2, the rectangular cavity resonator 1
In the long side direction of the rectangular cross section of 4, the end plates 9a and 9b for wavelength tuning are movably opposed to each other. The wavelength tuning movable end plates 9a and 9b can change the wavelength and the resonance frequency of the microwave standing wave formed in the rectangular cavity resonator 14 by moving in the arrow direction.

In the present microwave gas laser device, the long side of the rectangular cross section of the rectangular cavity resonator 14 is 70 mm,
The short side was 50 mm and the length in the laser optical axis direction was 300 mm. Metal end plates were used as the movable end plates 9a and 9b for wavelength tuning.

In the microwave gas laser device, the microwave electric field mode in the rectangular cavity resonator 14 is
As a result of measuring the electric field intensity distribution by the antenna inserted inside the rectangular cavity resonator 14, the one shown in FIG. 3 was obtained. From this figure, it was confirmed that the microwave electric field formed inside the rectangular cavity resonator 14 was the TE ₁₀ mode. 10 in FIG. 3 is a TE ₁₀ mode electric field vector.
Further, as shown in this figure, since the microwave standing wave has a wavelength of about 200 mm, it was found that the wavelength was close to the cutoff in the TE ₁₀ mode. Further, as can be seen from this figure, since the microwave standing wave formed in the laser optical axis direction of the discharge tube 1 has no node, the laser gas medium is discharged in the entire discharge tube. That is, the laser gas medium is discharge-excited with a half wavelength of the microwave standing wave (wavelength in the laser optical axis direction shown in FIG. 3A), and the half wavelength of the microwave standing wave is the laser gas. It is longer than the discharge length of the medium (hatched portion in FIG. 3).

Since the resonance frequency of the microwave standing wave is slightly deviated due to the generation of discharge plasma, the movable end plate 9 for wavelength tuning is further moved, and the insertion length thereof is finely adjusted to adjust the resonance frequency. The deviation can be corrected to stabilize the discharge. The laser output and oscillation efficiency at this time are shown in [Table 1]. The test results shown in [Table 1] are obtained under the conditions of a gas composition (a mixed gas of CO2, N2 and He, a pressure of 50 Torr) for a carbon dioxide gas laser as a laser gas medium. As shown in [Table 1], the effect of the wavelength tuning movable end plates 9a and 9b is that even if only the insertion length of one end plate 9a or 9b is finely adjusted, the insertion length of both end plates 9a and 9b is adjusted. Even if both are finely adjusted, the same effect can be obtained.

[0024]

[Table 1]

[0025]

As described above in detail with reference to the embodiments, according to the present invention, it is possible to generate a uniform discharge of the laser gas medium in the direction of the laser optical axis in the microwave gas laser device. The discharge excitation of the medium can be effectively performed. Therefore, the laser output and the oscillation efficiency can be improved.

[Brief description of drawings]

FIG. 1 is a front sectional view of a microwave gas laser device according to an embodiment of the present invention.

FIG. 2 is a side sectional view of a rectangular cavity resonator in the microwave gas laser device shown in FIG.

FIG. 3 is a schematic view of a microwave electric field mode in the rectangular cavity resonator of the microwave gas laser device shown in FIG.

FIG. 4 is a front sectional view of a conventional microwave gas laser device.

5 is a side sectional view of a cylindrical cavity resonator in the microwave gas laser device shown in FIG.

6 is a schematic view of a microwave electric field mode in the cylindrical cavity resonator of the microwave gas laser device shown in FIG.

[Explanation of symbols]

1 Discharge Tube 2 Microwave Oscillator 3 Waveguide 5 Total Reflection Mirror 6 Output Mirror 7 Laser Light 9a, 9b Wavelength Tuning Movable End Plate 10 TE ₁₀ Mode Electric Field Vector 14 Rectangular Cavity Resonator

Claims (6)

[Claims] 1. A microwave oscillated from a microwave oscillator is guided to a cavity resonator, and a laser gas medium in a discharge tube installed in the cavity resonator is discharge-excited by a microwave electric field to produce a laser output. In the obtained method for exciting a gas laser using a microwave discharge, a TE ₁₀ mode microwave electric field having an electric field direction perpendicular to an optical axis of laser light and having a substantially constant intensity is formed in the cavity resonator, and the microwave electric field is generated. A microwave discharge excitation method for a gas laser, characterized in that the laser gas medium is discharge-excited by an electric field. 2. The method for exciting a gas laser by a microwave discharge according to claim 1, wherein the laser is at a half wavelength of a microwave standing wave formed by a microwave electric field mode of TE _{10 in} the cavity resonator. A method for exciting a microwave discharge of a gas laser, which comprises exciting a gas medium by discharge. 3. The method of exciting a gas laser using a microwave discharge according to claim 1, wherein the cavity resonator is a rectangular cavity resonator having a predetermined dimension, and A microwave electric field of TE ₁₀ mode is formed on the substrate, and the length of the long side of the rectangular cross section of the rectangular cavity resonator is changed to determine the microwave constant formed in the rectangular cavity resonator. A microwave discharge excitation method for a gas laser, characterized in that the effective excitation length of a laser gas medium is controlled by changing the wavelength of the standing wave. 4. A microwave oscillator, a cavity resonator into which microwaves oscillated by the microwave oscillator are introduced, a discharge tube installed in the cavity resonator, and a laser gas in the discharge tube. A microwave gas laser device having a medium, the laser gas medium being discharge-excited by a microwave electric field formed in the cavity resonator to obtain a laser output. Microwave gas laser device comprising means for forming a TE ₁₀ mode microwave electric field in which the electric field direction is perpendicular to the optical axis and the intensity is substantially constant. 5. The microwave gas laser device according to claim 4, wherein the laser gas medium is ½ wavelength of the microwave standing wave formed by the microwave electric field mode of TE _{10 in} the cavity resonator. A microwave gas laser device comprising means for exciting discharge. 6. The microwave gas laser device according to claim 4 or 5, wherein the cavity resonator has a rectangular cavity resonance having a predetermined dimension for forming a TE ₁₀ mode microwave electric field therein. And the wavelength of the microwave standing wave formed in the rectangular cavity is changed by changing the length of the long side of the rectangular cross section of the rectangular cavity. A microwave gas laser device, wherein a movable end plate for wavelength tuning for controlling an effective excitation length of a gas medium is provided in the rectangular cavity resonator.