JPH02129976A - Microwave laser device - Google Patents

Abstract

PURPOSE:To enable an effective laser excitation to be made by connecting a microwave shield pipe to a discharge part so that the axis may be the same as laser optic axis and then discharging laser gas through the microwave shield pipe. CONSTITUTION:A microwave power 2 radiated from a microwave oscillator 1 is allowed to incide a discharge part 5 where low-pressure laser, gas is encapsulated through a barrier 4, a glow discharge 6 is formed here, and a laser gas 12 which is circulation-driven within the discharge part 5 is discharge- excited. With laser gas which is discharged and excited. excitation energy is shifted from N2 to CO2 while passing through a microwave shield pipe 7. The microwave shield pipe 7 is formed longer with a small diameter as compared with the wave length of microwave so that it take much time form laser gas to pass through. Thus, since stagnation time of laser gas within an optic resonator becomes longer, excitation energy of CO2 molecule is shifted effectively to laser beam. Thus, an effective laser excitation can be made.

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, Appli.

Phys, Lett, 37 (8), p6'a (19
80), a microwave laser device as shown in FIG. 4 has been proposed. That is, in FIG. 4, the laser gas 3
1 is supplied at high pressure from the upper part 32 of the discharge section, and as it passes through the nozzle 33 made of a dielectric material, the gas becomes high speed and the gas pressure decreases. On the other hand, microwaves 34 used for discharge excitation are supplied from the left side in the figure by a waveguide 35, and are supplied to the laser discharge section 41 through a pressure partition 36 that transmits microwaves.

Here, in the space of the laser discharge section 41, the space 37 in front of the nozzle 33 is under high pressure, so no discharge occurs in the space 37. On the other hand, the space 38 behind the nozzle 33
Since the gas pressure decreases in this area, microwave discharge occurs in this area.

The discharge in this part is uniform because it is a discharge in a low gas pressure. Light is amplified and oscillated. Further, the exhaust gas 40 is discharged in the direction shown in the figure by a vacuum pump.

(Problems 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, the laser gas 31 supplied at high pressure is passed through the nozzle 33.
In order to reduce the gas pressure by adiabatic expansion through the laser gas, a vacuum pump is required to exhaust the entire amount of laser gas. Moreover, the exhaust power of the vacuum pump becomes large, leading to an increase in the size of the apparatus, and the overall laser emission efficiency is extremely reduced.

In addition, since the flow of laser gas and the optical axis are perpendicular to each other,
The residence time of the excited laser gas within the optical resonator is short, resulting in a reduction in laser excitation efficiency. This kind of drawback is not so much of a problem with large lasers, which have a long optical path length and can have multiple optical paths to the discharge part by multiple diffractions, but if there is only one optical path in the discharge part and the beam is small. This has been a big problem for small lasers.

Generally speaking, if the residence time in the optical resonator is increased in order to eliminate the above-mentioned drawbacks, the flow velocity of the laser gas will decrease and the gas temperature will increase, which not only reduces the laser excitation efficiency but also increases the arc limit. There was also a drawback that the laser output was reduced.

The present invention was proposed to eliminate the above-mentioned drawbacks, and its purpose is to
, ) can be obtained, and by increasing the residence time of the laser medium gas in the optical resonator,
An object of the present invention is to provide a microwave laser device that can perform effective laser excitation.

[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 supply, the microwave shield tube is connected to the discharge part so that its axis is the same as the laser optical axis. , the laser gas is configured to be discharged through the microwave shield tube.

(Function) According to the microwave laser device of the present invention, the laser gas excited in the discharge section is discharged to the outside through the microwave shield tube, so the residence time of the laser gas in the optical resonator becomes longer. Excitation energy can be effectively transferred from N2 molecules to CO2 molecules.

(Example) Hereinafter, an example of the present invention will be specifically described based on FIG.

In this embodiment, as shown in FIG. 1, the microwave power 2 sent out from the microwave oscillator 1 is radiated into the waveguide 3. A partition wall 4 is provided inside the waveguide 3, and the waveguide 3 is connected to the microwave oscillator side 3.
It is divided into a microwave discharge tube side 3b and a microwave discharge tube side 3b. Further, a discharge section 5 is provided in the waveguide 3b on the side of the microwave discharge tube.
is connected. This discharge section 5 is composed of an introduction section 5a, a waveguide discharge section 5b, and an end section 5C, and the waveguide discharge section 5b is configured such that its cross-sectional area is smaller than that of the introduction section 5a and the end section 5G. has been done. Roughly, the discharge section 5
Microwave shield tubes 7 and 7' are arranged coaxially with the laser optical axis 8 on both sides of the microwave shield tube 7.
It is connected to the laser gas circulation pipe 10. On the other hand, the microwave shield tube 7- has a total reflection mirror 1 at its end.
3a is provided. Further, a blower 11 is provided in the middle of the circulation pipe 10, and is configured to circulate the laser gas 12 in the direction of the arrow. Further, a plurality of cooling pipes 15 are arranged around the waveguide discharge section 5b and the microwave shield tube 7. Further, an optical resonator is formed by the total reflection mirror 13a and the semi-transmission mirror 13b.

In the microwave laser device of this embodiment having such a configuration, the laser gas is excited by discharge as described below. That is, the microwave power 2 radiated from the microwave oscillator 1 passes through the partition wall 4 at a power of several tens of Torr.
The laser beam enters the discharge section 5 filled with a low-pressure laser gas of about r, forms a glow discharge 6 there, and discharge excites the laser gas 12 that is circulated inside the discharge section. While the laser gas discharge-excited in this manner passes through the microwave shield tube 7, the excitation energy is transferred from N2 to CO2. By the way, the microwave shield tube 7 is designed so that it takes time for the laser gas to pass through.
The diameter is sufficiently small compared to the microwave wavelength, and the diameter is sufficiently long. Therefore, the residence time of the laser gas in the optical resonator becomes longer, so the excitation energy of CO2 molecules is effectively transferred to the laser beam, and the laser output light is transmitted to the outside via the semi-transparent mirror 13b provided at the end. 14 is released. In addition, since the waveguide discharge part 5b and the shield tube 7 are cooled by the cooling pipe 15 disposed around the waveguide discharge part 5b and the microwave shield tube 7, the excitation to the upper level of the laser can be effectively performed. It can be done in a specific manner. Furthermore, the microwave shield tubes 7, 7- disposed on both sides of the discharge section 5 have a diameter sufficiently small compared to the wavelength of the microwave, and are sufficiently long. There will be no radio wave leakage inside.

In this manner, according to this embodiment, microwave energy is effectively injected into the waveguide discharge section, and a --like glow discharge is formed. In addition, since the residence time of the laser gas in the optical resonator can be increased, the discharge excitation energy can be smoothly transferred inside the microwave shield tube, and efficient amplification and oscillation of laser light can be performed. can.

It should be noted that the present invention is not limited to the above-mentioned embodiment, and two microwave shield tubes 21a and 21b may be arranged in the longitudinal direction of the rectangular waveguide 20 as shown in FIG. Good. In this case, two laser beams pass through the discharge part, but the electromagnetic field of the microwave inside the rectangular waveguide is as shown in Figure 3, so the electric field strength of the two laser beams is The laser beam passes through the area where the beam is strong, allowing effective laser excitation.

In addition, in the embodiments shown in FIGS. 1 and 2, the cross-sectional area of the discharge section is made small, but even if a microwave shield tube is installed in the conventional discharge section, the inside of the shield tube The residence time of the laser gas can be increased, and the discharge excitation energy can be smoothly transferred.

[Effects of the Invention] As described above, according to the present invention, a microwave shield tube is connected to the discharge part so that its axis is the same as the laser optical axis, and a laser gas is supplied through the microwave shield tube. A microwave laser device capable of effective laser excitation can be provided by increasing the residence time of the laser medium gas within the optical resonator by simply configuring the gas to be discharged to the outside. .

[Brief explanation of the drawing]

FIG. 1 is a configuration diagram showing one embodiment of the microwave laser device of the present invention, FIG. 2 is a perspective view showing another embodiment of the present invention,
FIG. 3 is a diagram showing the electric field distribution in a general rectangular waveguide, and FIG. 4 is a sectional view showing the main part of the conventional example. 1...Microwave oscillator, 2...Microwave power,
3... Waveguide, 4... Partition wall, 5... Discharge part, 5a
...Introduction part, 5b...Waveguide discharge part, 5C...End part, 6...Glow fIi electric current, 7,7-...Microwave shield tube, 8...Laser optical axis , 10... Laser gas circulation pipe, 11... Blower, 12... Laser gas, 13a... Total reflection mirror, 13b... Half-transmission mirror, 20... Rectangular waveguide, 2'la, 21b...Microwave shield tube, 31...Laser gas, 32...
- Upper inlet, 33... Nozzle, 34... Microwave, 35... Waveguide, 36... Pressure bulkhead, 39...
Optical camera camera, 40... Exhaust gas, 41... Laser discharge unit.

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, a microwave shield tube is connected to the discharge section so that its axis is the same as the laser optical axis, and the laser gas is discharged through the microwave shield tube. A microwave laser device characterized in that it is configured to.