JPH04326778A - Microwave-excited vapor laser - Google Patents

Abstract

PURPOSE:To improve an output and an oscillation efficiency of a laser by uniformly exciting to discharge laser gas medium in a discharge tube only with a TM010 mode adapted for a laser oscillation from a various microwave electromagnetic field mode in a cylindrical cavity resonator in a laser oscillator to be excited to be discharged by an electromagnetic wave of a microwave range. CONSTITUTION:A microwave to be output from a microwave oscillator 2 is transmitted to a cylindrical cavity resonator 4 through a waveguide 3. The waveguide 3 is connected to the resonator 4 through a coaxial tube made of an outer conductor 10 and an inner conductor 11. A totally reflecting mirror 5 and an output mirror 6 are oppositely arranged at both ends of a discharge tube 1. The conductors 10, 11 of the coaxial tube are connected by a looplike antenna 12 at its lower end. The tube is so movable that at least one of the conductors 10, 11 is adjustable in an insertion length into the resonator 4.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a laser oscillator that is discharge-excited by electromagnetic waves in the microwave region.

0002

2. Description of the Related Art A conventional laser device will be explained with reference to FIGS. 5, 6 and 7. FIG. 5 is a front sectional view showing the configuration of a conventional laser device, and FIG. 6 is a side view of a cylindrical cavity resonator. Further, FIG. 7 is a diagram showing an electric field vector within a cylindrical cavity resonator.

In FIGS. 5 and 6, a discharge tube 1 is inserted and installed in the axial direction into a cylindrical cavity resonator 4 connected to a microwave oscillator 2 via a waveguide 3, and its both ends are connected to a cylindrical cavity resonator 4. A total reflection mirror 5 and an output mirror 6 are installed in the
Microwaves output from the microwave oscillator 2 propagate in the waveguide 3, and are transmitted to the cylindrical cavity resonator 4 via the coupling portion 8 opened to the size of the transmission waveguide shown in FIG. Laser gas within the discharge tube 1 is excited to discharge by the electric field of the microwave. As a result, stimulated emission light is obtained from the laser gas medium, and the total reflection mirror 5 that forms the optical resonator
The laser beam 7 is amplified by reciprocating reflection between the output mirror 6 and the output mirror 6, and the laser beam 7 transmitted through the output mirror 6 is taken out.

[0004] A discharge excitation method of a laser gas using microwaves is described by Handy and Brandelik, J. A
ppl. Phys. , 49, 3753-3756 (19
78). It is already known by. However, when using a cavity sealed with microwaves, it is possible to discharge excite the laser medium, but the microwave standing waves that can be formed in a normal cavity are TM or TE mode (T
(transverse Electric Mode), in which a large number of devices coexist, so if the opening of the cavity at the coupling part between the transmission waveguide and the cylindrical cavity resonator is the same as the size of the transmission waveguide, as shown in Fig. 7. Since the microwave electromagnetic field acting on the discharge has complex and diverse wave motions, the microwave electric field strength is not constant in the axial direction of the discharge tube. Therefore, since the laser gas medium in the entire discharge tube cannot be discharge-excited and the electric field of the discharge is concentrated in a local space within the discharge tube, the temperature of the generated discharge plasma increases, which increases the energy level that contributes to laser oscillation. Since population inversion becomes difficult to establish, there are drawbacks such as low laser output and oscillation efficiency.

[0005]

[Problems to be Solved by the Invention] The present invention has been made to solve the above-mentioned problems of the conventional laser device. Only in TM010 mode,
An object of the present invention is to provide a microwave-excited gas laser device that can uniformly discharge-excite a laser gas medium in a discharge tube and improve laser output and oscillation efficiency.

[0006]

[Means for Solving the Problems] In order to achieve the above object, the microwave excited gas laser device of the present invention includes a cylindrical cavity resonator, a microwave oscillator, and a microwave oscillated by the microwave oscillator. a waveguide that supplies the cavity resonator; a discharge tube inserted into the cavity resonator in the axial direction;
In a microwave-excited gas laser device comprising an optical resonator made of mirrors arranged at both ends of the discharge tube,
The waveguide and the cavity resonator are communicated through a coaxial tube, and the coaxial tube is movable so that the insertion length of at least one of the inner tube and the outer tube into the cavity resonator can be adjusted. The present invention is characterized in that the tip of the coaxial inner tube and a part of the outer tube are connected by a conductor to form a loop-shaped antenna.

[0007]

[Operation] The microwave-excited gas laser device of the present invention introduces microwaves output from a microwave oscillator into a cylindrical cavity resonator, and includes a discharge tube that generates a discharge by the electric field, a total reflection mirror, and In a laser oscillator configured with an optical resonator consisting of an output mirror, a coaxial tube is installed at the coupling part of the microwave transmission waveguide from the microwave oscillator and the cylindrical cavity resonator, and the coaxial tube is connected inside the cavity. By making a loop-shaped antenna by contacting the inner conductor with a part of the outer conductor, the transmitted microwave becomes a uniform microwave electric field in the axial direction of the discharge tube inside the cavity resonator in the TM010 mode (Transverse mode).
Magnetic Mode (010 is a subscript expressed by a Bessel function of the first type) is formed to obtain a discharge in a single resonance mode, and the entire laser gas in the discharge tube in the cylindrical cavity resonator is excited by discharge. be able to.

Furthermore, by adjusting the insertion length of the coaxial tube into the cavity, the microwave power into the cavity can be controlled, so that it is not affected by load fluctuations caused by fluctuations in plasma density within the discharge tube.

Then, by using the cylindrical cavity resonator coupled with the above-mentioned coaxial tube, the localization of the discharge in the axial direction of the discharge tube and the rise in temperature of the discharge plasma are suppressed, and all of the laser gas medium in the discharge tube is suppressed. Population inversion formation of energy levels suitable for laser oscillation can be achieved by discharge excitation and plasma temperature setting.

0010

DESCRIPTION OF THE PREFERRED EMBODIMENTS A device according to an embodiment of the present invention will be explained below with reference to the drawings. Figure 1 is a front sectional view of a gas laser device using a cylindrical cavity as the cavity, Figure 2 is a side view of the cylindrical cavity coupled to a transmission waveguide, and Figure 4 is a coaxial tube. FIG. 3 is a perspective view showing a connected state of an inner cylinder and an outer cylinder. Further, FIG. 3 shows a schematic diagram of the microwave electromagnetic field mode according to the apparatus of this embodiment. 5 to 7 described above in these figures.
The same parts are given the same symbols.

In FIGS. 1, 2 and 4, a discharge tube 1 is inserted into a cylindrical cavity resonator 4 in the axial direction thereof. A total reflection mirror 5 and an output mirror 6 are arranged opposite to each other at both ends of the discharge tube 1, and the microwave output from the microwave oscillator 2 is transmitted into the cylindrical cavity resonator 4 via the waveguide 3. Ru. In this case the waveguide 3 and the cavity resonator 4
As shown in Figure 4, the outer conductor 10 and inner conductor 11 of the coaxial tube
It is configured to connect via a coaxial tube consisting of
In addition, since the lower end of the outer conductor 10 and the lower end of the inner conductor 11 of the coaxial tube are connected in contact with each other by the loop antenna 12, the transmitted microwave is transmitted inside the cavity resonator 4 in the axial direction of the discharge tube. A uniform microwave electric field strength is created, and the entire discharge tube within the cavity is uniformly discharged.

The cylindrical cavity resonator 4 shown in FIG. 2 has an inner diameter of 8.
6 cm, length 20 cm, and the insertion length of the loop antenna 12, which is attached to the coupling part of the transmission waveguide and the cylindrical cavity resonator, and a part of the outer conductor 10 of the coaxial tube and the inner conductor 11 are brought into contact with the conductor. 1.0 cm, the electromagnetic field strength inside the cylindrical cavity resonator 4 is constant in the axial direction of the discharge tube 1, as seen from the electric field vector 9 shown in FIG. 3, so that the entire discharge tube inside the cavity is uniform. discharge to. It was found that under these coaxial tube insertion conditions, the reflection of microwaves to the microwave oscillator in the cylindrical cavity resonator was almost zero, and the microwaves were efficiently transmitted into the cavity. Table 1 shows the laser output and oscillation efficiency obtained using a carbon dioxide laser gas medium.

[0013]

[Table 1]

On the other hand, no coaxial pipe is provided at the connection between the transmission waveguide and the side surface of the cylindrical cavity resonator, and as shown in FIG. 6 of the conventional device, the waveguide from the microwave oscillator is directly coupled to the side surface of the cavity. Table 1 shows the laser output and oscillation efficiency for comparison. In the case of the conventional device, as shown in FIG. 7, the electric field is not constant in the axial direction of the discharge tube, and the discharge is non-uniform. Furthermore, under this condition, the amount of reflected microwaves from the cavity resonator is large, so as shown in Table 1, the laser output and oscillation efficiency are low.

In the device of this embodiment, the outer cylinder of the coaxial tube (
At least one of the outer conductor 10) or the inner cylinder (inner conductor 11) is configured to be movable up and down in the direction of the arrow in FIG. 4 so that the length of insertion into the cavity resonator 4 can be adjusted. Microwave power can be controlled. Note 1
A sleeve 3 is fixed to the outer wall of the cylindrical cavity resonator 4, and the coaxial tube is guided by the sleeve 13. In the case of FIG. 4, an example is shown in which the inner cylinder and the outer cylinder of the coaxial tube are configured to move up and down together.

[0016]

[Effects of the Invention] According to the present invention, in the laser device,
A uniform discharge of laser gas can be generated in the axial direction of the discharge tube, and the discharge excitation of the laser gas in the discharge tube installed in the cylindrical cavity resonator can be effectively performed.

[Brief explanation of drawings]

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

FIG. 2 is a side view of a cylindrical cavity resonator in the laser device of FIG. 1;

FIG. 3 is a schematic diagram of a microwave electromagnetic field mode in an embodiment of the present invention.

FIG. 4 is a perspective view showing how a coaxial tube is attached in an apparatus according to an embodiment of the present invention.

FIG. 5 is a front sectional view schematically showing a conventional laser device.

FIG. 6 is a side view of a cylindrical cavity resonator in the device.

FIG. 7 is a schematic diagram of an electric field mode in a conventional device.

[Explanation of symbols]

1 Discharge tube 2 Microwave oscillator 3 Waveguide 4 Cylindrical cavity resonator 5 Total reflection mirror 6 Output mirror 7 Laser beam 8 Waveguide and cavity resonator coupling part 9 Electric field vector 10 Coaxial tube (outer conductor) 11 Coaxial Tube (inner conductor) 12 Loop antenna 13 Sleeve

Claims (1)

[Claims] 1. A cylindrical cavity resonator, a microwave oscillator, a waveguide for supplying the microwave oscillated by the microwave oscillator to the cavity resonator, and axially inserted into the cavity resonator. In a microwave-excited gas laser device, the waveguide and the cavity resonator are communicated via a coaxial tube in a microwave-excited gas laser device comprising a discharge tube and an optical resonator made of mirrors arranged at both ends of the discharge tube. At the same time, the length of insertion of at least one of the inner tube and the outer tube of the coaxial tube into the cavity resonator can be adjusted, and
A microwave-excited gas laser device characterized in that the tip of the coaxial tube inner tube and a part of the outer tube are connected by a conductor to form a loop-shaped antenna.