JPH08148748A - Gas laser oscillator provided with external mirror - Google Patents

Abstract

PURPOSE: To eliminate mirror angle adjustment, increase a laser power rise up speed and reduce power fluctuation due to environmental temperature change by keeping the whole body at a fixed temperature by heat-control of the parts of a plurality of rod components of a gas laser oscillator provided with external mirrors. CONSTITUTION: A gas laser oscillator provided with external mirrors is provided with cylindrical metal rod components 4a-4c, which penetrate plate components 3a-3d formed of metal plate that has an opening at the center to permit a laser tube 1 to fit and are fixed by a rod fixing screw 17. Heaters 11a-11c are wound on the rod components 4a-4c, and temperature sensors 12a-12c are provided between the rod components 11a-11c and the heaters 11a-11c. Signals of the temperature sensors 12a-12c are transmitted from temperature measurement parts 10a-10c to temperature controllers 9a-9c so as to operate heat power sources 8a-8c and the oscillator is heated and kept at a fixed temperature.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an external mirror type gas laser oscillator, and more particularly to stabilizing the output by controlling the temperature of a resonator.

[0002]

2. Description of the Related Art A conventional external mirror type gas laser oscillator will be described with reference to FIG.

FIG. 4 is a diagram showing a structure of a conventional external mirror type gas laser oscillator, and FIG. 5 is a sectional view taken along line A in FIG.

Three rod parts 4a to 4c made of a metal material having a low thermal expansion such as a cylindrical Invar material are formed of a metal plate such as aluminum with an opening for fitting the laser tube 1 in the center. The plate parts 3a to 3d that have been
It is fixed with a rod fixing screw 17. Rod parts 4a
The relative position between ~ 4c is located at the apex of a right triangle,
And they are arranged to be in equilibrium.

The plate parts 3b and 3c are filled with a laser medium such as argon gas, krypton gas, or a mixed gas of helium and neon, and the laser tube 1 having a cathode 13 and an anode 14 for discharge is formed at a right angle. It is arranged in parallel with the rod parts 4a to 4c at the position of the midpoint of the long side of the triangle, and is fixed by the laser tube fixing part 16.

On the outside of the plate parts 3a and 3d at both ends, a laser tube 1 is provided by springs 6a to 6c (6c is not shown) and adjusting screws 7a to 7c (7c is not shown), respectively.
Mounted are variable plates 5a and 5b formed of a metal plate such as aluminum whose angle with respect to the central axis can be changed. The laser tube 1 is attached to the variable plates 5a and 5b.
And a pair of laser mirrors 2a and 2b forming an optical resonator are fixed on the extension line of the central axis of the laser tube 1.

When the laser oscillator is operated, the laser tube 1
Electric discharge occurs inside and heats up. The temperature of the rod parts 4a to 4c rises due to heat transfer of radiation, conduction, and convection, and the rod parts 4a to 4c thermally expand. Since the cathode 13 of the laser tube 1 requires an operating temperature of 1000 ° C. or higher, it is the portion that generates the most heat. The cathode 13 terminal also exceeds 100 ° C.

For this reason, the temperature distribution can be made in the rod part 4a, and the temperature around the cathode 13 becomes the highest. Also,
Since a temperature difference due to convection is also possible, the temperature of the lot component 4a at a high position becomes higher than the temperatures of 4b and 4c. From the above, the three rod components 4a to 4c do not have a well-balanced thermal expansion, and therefore have different lengths. As a result, the angles of the laser mirrors 2a and 2b with respect to the central axis of the laser tube 1 change and a deviation from the optimum angle (90 °) occurs, and the laser output decreases, so it is necessary to adjust the angle of the laser mirror. Further, since only the heat generated by the discharge serves as a heat source for heating the rod parts, it takes a time until the output reaches the thermal equilibrium, and the output changes depending on the environmental temperature.

FIG. 6A to FIG. 6A for the case of the conventional angle adjustment.
6d will be described. 6a to 6d are schematic configuration diagrams in which only the basic constituent elements of FIG. 4 are drawn, FIG. 6a shows a state before the operation, and FIG. 6b shows a state where the laser mirror angle is not adjusted after the operation. 6C is a diagram showing a state after adjustment of the laser mirror angle after the operation, and FIG. 6D is a diagram showing a state in which the operation is stopped and cooled in the state of FIG. 6C.

When the laser oscillator is operated, the rod component 4a has a larger thermal expansion than the other two rod components due to the reason described above. It becomes a letter shape. Therefore, the angles of the laser mirrors 2a and 2b with respect to the central axis of the laser tube 1 change, and the laser output decreases. Therefore, in order to maximize the output in a stable state when the temperature of the laser tube rises,
The adjustment screws 7a to 7c are adjusted against the springs 6a to 6c to obtain the optimum angle state as shown in FIG. 6c. The operation is stopped in this state as shown in FIG. 6d. Therefore, in the subsequent operation, when operating under the same conditions, as shown in FIG.
c will be repeated. This state change from FIG. 6d to FIG. 6c has the disadvantage that it takes time for the reasons mentioned above.

As a conventional example, there is a technique in which the length of the laser resonator is changed by thermal expansion. Since these techniques are different from the purpose of the present invention, a brief introduction will be given.

In Japanese Patent Laid-Open No. 2-105483, FIG.
A technique for controlling the length of the resonator 70 is disclosed as shown in FIG. This is one resonator support rod 71 with a heater 74
The temperature is controlled by passing water for cooling inside. In this technique, the metal resonator support rod 71 has an example of an iron rod having a length of 100 mm. However, in this configuration, the reaction speed with respect to temperature control is slow, the output rising characteristic is improved, and the discharge current is changed. It takes time to respond to the output change in the case of making it. In particular, a water-cooled argon laser having a long length of 1 m or more has a large heat capacity, and this tendency becomes large.

Further, Japanese Patent Application Laid-Open No. 1-238081 discloses a technique of a wavelength stabilized laser oscillator as shown in FIG. Here, the oscillation wavelength is changed by utilizing the thermal expansion of the laser resonator 82, and it is described as a technique of controlling the temperature by the heater 83.

Further, Japanese Laid-Open Patent Publication No. 1-310584 discloses a technique of a single frequency adapter for a laser for the purpose of stabilizing a single frequency, suppressing a mode hop and stabilizing an output as shown in FIG. Is disclosed. This is a technique for arranging an induction coil 94 around a metal mirror mounting portion 92, controlling the extension of the mirror mounting portion 92 by high frequency induction heating, and changing the resonator length to perform single frequency oscillation. Although the heating means is disclosed, since it uses induction heating, it cannot be applied to a rod part made of an insulator such as glass which is one of low thermal expansion materials.

[0015]

In this conventional external mirror type gas laser oscillator, it is necessary to adjust the angle of the laser mirror with a screw so as to maximize the output in the heat equilibrium state, and only the heat generated by the discharge is generated. For this reason, there is a problem in that it takes time for the output to rise to a thermal equilibrium state, and the output also changes depending on changes in the environmental temperature.

Further, even if the discharge current is changed, the amount of heat generated changes accordingly. Therefore, when the discharge current is changed, the angle with respect to the central axis of the laser mirror is deviated, and the output of the laser tube 1 with the full capacity can be obtained. There was also the problem of not having it.

The external mirror type gas laser oscillator of the present invention solves the problems of these prior art examples. It eliminates the adjustment of the mirror angle by screws, accelerates the rise of the laser output, improves the output stability, and improves the environment. The purpose is to reduce the amount of output change due to temperature change.

[0018]

The external mirror type gas laser oscillator of the present invention comprises a laser tube, a pair of laser mirrors arranged at both ends, a plurality of plate parts for supporting the laser tube and the laser mirror, and A plurality of rod parts for fixing the plate parts, a plurality of temperature sensors for dividing the rod parts into a plurality of parts in the longitudinal direction and measuring the temperature of the rod parts at each part, and a plurality of heaters for heating the rod parts. And a plurality of temperature control units that change the output voltage of the heater power supply according to a signal from the temperature sensor.

[0019]

The heater is divided in the longitudinal direction of the plurality of rod parts constituting the laser resonator of the external mirror type gas laser oscillator, and the heater is wound around a plurality of parts, and each heater is individually heated and the temperature of each rod part is controlled so that each rod part is separated. It can be thermally expanded to maintain a constant length for each rod component. In addition, by heating from the outside, the rising characteristic of the laser output can be accelerated accordingly.

[0020]

The present invention will be described below with reference to the drawings. FIG. 1 shows an external mirror type gas laser oscillator according to an embodiment of the present invention.

The rod parts 4a to 4c made of a metal material such as a columnar invar material are plate parts 3a to 4c made of a metal plate such as aluminum with an opening into which the laser tube 1 is fitted. Rod fixing screw 17 that penetrates 3d
It is fixed at.

The relative positions of the rod parts 4a to 4c are located at the vertices of a substantially right triangle and arranged so as to be parallel to each other.

The plate parts 3b and 3C are filled with a laser medium such as argon gas, krypton gas, or a mixed gas of helium and neon, and the laser tube 1 provided with a discharge cathode 13 and an anode 14 has a right-angled triangular shape. It is arranged parallel to the rod parts 4a to 4c at the position of the midpoint of the long side and is fixed by the laser tube fixing part 16.

Springs 6a to 6c and adjusting screws 7a to 7c are provided outside the plate parts 3a and 3d at both ends, respectively.
A variable plate 5 formed of a metal plate such as aluminum whose angle with respect to the central axis of the laser tube 1 can be changed by
a and 5b are attached. This variable plate 5
Laser mirrors 2a and 2b forming an optical resonator with the laser tube 1 are fixed to a and 5b on the extension line of the central axis of the laser tube 1.

Taking a water-cooled argon laser as an example of the external mirror type gas laser oscillator, rod parts 4a to 4 will be described.
The length of c is about 1000 mm with a 4 W output oscillator. The cavity distance between the laser mirrors 2a and 2b is 1100 mm.
It is a degree. As materials for the rod components 4a to 4c, Invar and Super Invar, which are low thermal expansion materials, are used as materials for suppressing thermal expansion. Further, the plate components 3a to 3d, the variable plates 5a to 5b, etc. are made of a lightweight aluminum alloy in order to reduce the deflection of the rod components.

The rod parts 4a to 4c include heaters 11a.
~ 11c are respectively wound, and further temperature sensors 12a-12
c is installed between the rod parts 4a-4c and the heaters 11a-11c. The signals of the temperature sensors 12a to 12c are supplied from the temperature measuring units 10a to 10c, respectively.
The heater power supplies 8a to 8c are operated via c to heat them to a constant temperature and keep them warm.

Although FIG. 1 shows three temperature control systems for the rod 4b, the rod parts 4a and 4c are similarly constructed. These six temperature control systems are omitted for simplification of the drawing.

Here, for example, in the case of a water-cooled argon laser of 2 W output, a rod component 4 made of Invar material having a length of 1 m.
The highest temperature among a to 4c is in the vicinity of the cathode 13 and reaches 40 ° C. when the environmental temperature (room temperature) is 20 ° C., and the temperature rises by 20 ° C. In this case, for example,
The temperature may be set to 40 ° C + 10 ° C = 50 ° C with a margin of + 10 ° C above the ambient temperature.

This is because a simple structure in which the active cooling is not necessary and the temperature is kept only by the ON-OFF control of the heater.

The actual ambient temperature for operating the laser is 0 ° C. to 40 ° C., which is widely estimated. In order to prevent the laser output from changing due to changes in the ambient temperature, heat generated by the laser operation at the ambient temperature upper limit of 40 ° C
When the temperature rises by 0 ° C, the temperature is 60 ° C, so that the temperature is further increased by + 10 ° C and kept at 70 ° C. Most of the operating conditions can be satisfied if the heat retention temperature is within a heating range of + 10 ° C. to + 30 ° C. with respect to the higher one of the environmental temperature and the maximum attainable temperature of the rod portion. Also, overheating at the time of startup is expected, but the set temperature is lowered by several degrees Celsius, for example 65
The solution is to set a heat retention temperature at ℃.

As a result, as shown in FIG. 2b, the rod parts 4a to 4c before the discharge start as shown in FIG. 2a are heated and kept at 50 ° C. regardless of the ambient temperature after the start of the discharge of the laser tube 1. The rod components 4a to 4c uniformly thermally expand. At this time, if the temperature rising speed (temperature and time) is the same for the rod portions 4a to 4c, the laser mirror 2
The angle between a and 2b and the central axis of the laser beam is not deviated from the optimum angle of 90 °, and the rise time of the output is shortened.

The laser tube 1 generates a large amount of heat due to discharge. Therefore, in order to prevent the laser tube 1 from being broken, it is necessary to actively cool it by water cooling or air cooling as usual. The cooling system is omitted for simplification of the drawing.

The heat generated from the heaters 11a to 11c of the present invention is smaller than the heat generated from the laser tube 1 itself, and since the positive cooling is also performed, the influence on the laser tube 1 can be ignored.

From the above, the rising characteristics of the laser output,
Improved output stability and environmental characteristics. Further, even when the discharge current was changed to adjust the output, the reaction of the output became faster. In the present embodiment, the plate parts 3b and 3c to which the rod parts are fixed are divided into three sections, but the temperature of the rod parts is increased by further dividing the adjacent plates into two and three parts. The distribution becomes more uniform, and the effect of the present invention can be further improved. <Second Embodiment> A second embodiment will be described with reference to FIG. In the second embodiment, as shown in the drawing, the heaters 11a to 11c wound in a plurality of parts in the longitudinal direction of the rod component 4b are connected in series, and the heater power supply 8a, the temperature control unit 9a, and the temperature measuring unit 1 are connected.
0a and one temperature sensor 12a. Although the rods 4a and 4c have the same structure, although not shown in the drawing, it is possible to use only three temperature control systems as a whole.

With respect to the temperature difference between the respective parts, the difference in the amount of heat generated is provided by changing the length of the heater. Obviously, the same effect can be obtained by changing the resistance value by changing the wire diameter and the wire material.

The same effects as those of the first embodiment can be expected in the second embodiment.

[0037]

As described above, according to the present invention, the plurality of rod parts 4a to 4c of the external mirror type gas laser oscillator are divided into a plurality of parts, and the heating temperature control by the heater is performed for each part, so that the whole is kept constant. Since the temperature is maintained, the rise characteristic of the laser output becomes faster, and the stability after output saturation is also improved. Further, it has a result that the output change amount due to the environmental change is also small.

[Brief description of drawings]

FIG. 1 is a configuration diagram of an external mirror type gas laser oscillator that is a first embodiment of the present invention.

FIG. 2 a. Schematic configuration diagram of the external mirror type gas laser oscillator of the present invention before operation. B. Schematic configuration diagram during operation of the external mirror type gas laser oscillator of the present invention

FIG. 3 is a configuration diagram of a second embodiment of the present invention.

FIG. 4 is a block diagram of a conventional external mirror type gas laser oscillator.

5 is a cross-sectional view taken along the line AA in FIG.

FIG. 6 a. Schematic configuration diagram of a conventional external mirror type gas laser oscillator before operation b. Schematic configuration diagram of the conventional external mirror type gas laser oscillator during operation, not adjusted c Schematic configuration diagram of the conventional external mirror type gas laser oscillator after operation, and after adjustment of the conventional external mirror type gas laser oscillator Schematic configuration diagram

FIG. 7 is a diagram showing a first embodiment of the prior art.

FIG. 8 is a diagram showing a second embodiment of the prior art.

FIG. 9 is a diagram showing a third embodiment of the prior art.

[Explanation of symbols]

 1 Laser tube 2a, 2b Mirror 3a-3d Plate part 4a-4c Rod part 5a, 5b Variable plate 6a-6c Spring 7a-7c Adjustment screw 8a-8c Heater power supply 9a-9c Temperature control part 10a-10c Temperature measuring part 11a- 11c Heater 12a-12c Temperature sensor 13 Cathode 14 Anode 15 Capillary tube 16 Laser tube fixing part 17 Rod fixing screw

Claims (2)

[Claims] 1. A laser tube, a pair of laser mirrors arranged at both ends, a plurality of plate parts for supporting the laser tube and the laser mirror, and a plurality of rod parts for fixing the plate parts. In the external mirror type gas laser oscillator, each rod component is divided into a plurality of parts in the longitudinal direction, a plurality of temperature sensors for measuring the temperature of the rod component at each part, and a plurality of heaters for heating the rod component. And a plurality of temperature control units that change the output voltage of the heater power supply according to a signal from the temperature sensor, and keep the temperature higher by a predetermined value than either the ambient temperature or the highest rod temperature reached. An external mirror type gas laser oscillator characterized by the above. 2. The external mirror type gas laser oscillator according to claim 1, wherein the predetermined value is from + 10 ° C. to +
An external mirror type gas laser oscillator characterized in that the temperature is 30 ° C.