JP2000261065A - Metal vapor laser - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a metal vapor laser device that suppresses instability of initial electric discharge caused by a buffer gas for discharge in an electric- discharge tube, and instability of laser oscillation caused following it. SOLUTION: In a metal vapor laser, a vapor source metal 33 is held in an electric-discharge tube body 11, and a discharging buffer gas of a prescribed pressure is introduced, and initial electric discharge is generated by applying a voltage, and the vapor source metal is vaporized to be introduced into laser oscillation. In the metal vapor laser, a photoelectric conversion element 31 is placed in a condition where it can detect initial electric discharge light which exits from the electric-discharge tube main body generated by discharging buffer gas, and an initial electric discharge condition generated by the discharging buffer gas in the electric-discharge tube body is detected with the photoelectric transfer element, and the initial electric discharge condition is controlled with a feedback thereof.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a metal vapor laser device, and more particularly to a method for detecting deterioration of initial discharge characteristics due to a discharge buffer gas in a discharge tube body in a short time, and based on the detected discharge characteristics. The present invention relates to a metal vapor laser device capable of improving the initial discharge state.

[0002]

2. Description of the Related Art As shown in FIG. 3, in a metal vapor laser apparatus 101, a vacuum pump 128 is operated to evacuate the inside of a discharge tube body 111, and then the gas supply pipe 1 is evacuated.
20, for example, neon gas is injected into the discharge tube main body 111 as a discharge buffer gas,
By applying an excitation pulse voltage between the cathode 117 and the anode 116, plasma is generated in the discharge tube main body 111. This plasma causes the discharge tube body 111
Is the vapor source metal 1 set inside the discharge tube main body 111.
33 is heated to a temperature at which metal vapor can be generated.

The metal vapor generated from the vapor source metal 133 is uniformly distributed in the discharge tube body 111 whose temperature has been increased and maintained at a substantially constant temperature. By continuing this state, free electrons in the plasma collide with the metal vapor to excite the metal vapor, and eventually the inside of the discharge tube main body 111 has a population inversion state. In this population inversion state, a laser beam is generated when the excited metal vapor transitions to a low energy level.

[0004] The laser beam generated in the discharge tube main body 111 passes through a window 122a, which is provided on an extension of the optical axis direction.
122b, the output mirror 123 and the total reflection mirror 1
The light is repeatedly reflected between the output mirror and the output mirror 123, and the amplitude thereof is increased during that time.

In the above-described metal vapor laser device, air is contained in the buffer gas immediately after disassembly and assembly due to the installation and replenishment of the vapor source metal during maintenance, and when restarting operation after a long operation stop. In addition to the deterioration of the discharge characteristics of the discharge gas due to mixing of water and moisture, it is known that the discharge resistance becomes higher due to air or moisture adhering to the structural material such as the discharge tube body 111 and the discharge becomes unstable. Have been.

The deterioration of the initial discharge characteristics due to the discharge buffer gas has a problem in that the discharge plasma comes into contact with the inner side surface of the discharge tube main body 111 and the discharge main body 111 is damaged. Also, as the discharge resistance increases,
An accident such as abnormal overheating of the circuit element of the power supply circuit 130 or damage to the circuit element may occur.

Therefore, immediately after maintenance or after restart for a long time, the discharge pump body 111 is evacuated by operating the exhaust pump 128, and then the discharge buffer gas is discharged from the gas supply pipe 120. It is necessary to repeat the deaeration step of injecting into the 111 and discharging it a predetermined number of times.

[0008]

Conventionally, the above-mentioned phenomena such as deterioration of initial discharge characteristics and increase in discharge resistance due to the discharge buffer gas are monitored by a monitoring person by visual observation of the state of initial discharge. Is normal. For this reason,
When the operation of the laser device is started, there is a disadvantage that a person who monitors the state of discharge must be always arranged.

As a method of detecting a change in the output of discharge light due to deterioration of discharge characteristics and an increase in discharge resistance, a method of detecting a decrease in discharge current has been proposed, but the amount of change in discharge current is small. Therefore, it is insufficient to detect the deterioration of the discharge characteristics and the increase of the discharge resistance with high accuracy in a short time.

SUMMARY OF THE INVENTION In view of the above-mentioned problems, an object of the present invention is to detect instability or deterioration of an initial discharge caused by a discharge buffer gas in a discharge tube more accurately in a short time, and to stably and efficiently detect a metal vapor laser based on the detection. An object of the present invention is to provide a metal vapor laser device that can lead to oscillation and that can prevent damage to circuit elements of a discharge circuit serving as a power supply device, breakage of a discharge tube main body, and the like.

[0011]

SUMMARY OF THE INVENTION According to the present invention, a photoelectric conversion element is arranged so that initial discharge light emitted from the inside of a discharge tube body by a discharge buffer gas can be detected. This is a metal vapor laser device configured to detect an initial discharge state due to a buffer gas for use, and to appropriately control the initial discharge state based on feedback of electric or the like.

[0012]

Embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 1 is a schematic view showing an example of the metal vapor laser device of the present invention.

As shown in FIG. 1, a metal vapor laser device 1
A laser resonator 2 for outputting a laser beam, a gas supply unit 3 for supplying a discharge buffer gas to the laser resonator 2,
A gas exhaust unit 4 for exhausting a discharge buffer gas that has contributed to the discharge from inside the laser resonator 2, and supplies a pulsed DC voltage for outputting a laser beam to the laser resonator 2 filled with the discharge gas. The high-voltage power supply device 5, the gas supply unit 3 and the gas exhaust unit 4 are controlled to output the laser gas from the discharge gas control unit 6 and the laser resonator 2 which maintain the state of the discharge gas inside the laser resonator 2 in an optimum state. An initial discharge monitoring unit 7 monitors the state of the initial discharge by the discharge buffer gas. In addition, each of the gas supply unit 3, the gas exhaust unit 4, the high-voltage power supply device 5, the discharge gas control unit 6, and the initial discharge monitoring unit 7 is connected to the main control device 8.

The discharge tube, that is, the laser resonator 2 is made of, for example, a discharge tube main body 11 made of ceramics such as alumina (Al 2 O 3), a heat insulating material 12 covering the discharge tube main body 11, and an insulating material surrounding the heat insulating material 12. The tube 13 comprises a metal outer tube 14 further surrounding the insulating tube 13. The outer tube 14 is composed of two outer tubes 15a and 15b divided at a substantially central portion in the longitudinal direction of the discharge tube main body 11, and is controlled between the two outer tubes (15a and 15b) by the control of the main controller 8. A predetermined drive voltage is supplied from the high-voltage power supply 5.

An anode 16 and a cathode 17, which are provided at a distance in the axial direction from the discharge tube main body 11, are connected to both ends of the discharge tube main body 11 in the axial direction by heat insulating material 12 so as to face each other. . The anode 16 and the cathode 17 are electrically connected to the outer tubes 15a and 15b, respectively, by electrode flanges 18a and 18b connected to the outer tubes 14 (15a and 15b).

A pair of Brewster tubes 19a and 19b are connected to the extension of the anode 16 and the cathode 17 in the optical axis direction. The left blaster pipe 19a has a gas supply pipe 20 enabling connection to the gas supply unit 3, and the right blaster pipe 19b has a gas exhaust pipe 21 enabling connection to the gas exhaust unit 4. Are provided respectively.

Windows 22a and 22b are provided on the Brewster tubes 19a and 19b, respectively, on the extension in the optical axis direction. An output mirror 23 for outputting a laser beam is provided on an extension of the window 22a provided on the left Brewster tube 19a in the optical axis direction, and a right Brewster tube 19b is provided.
A total reflection mirror 24 for amplifying a laser beam in the discharge tube main body 11 is provided on an extension of the window 22b provided in the discharge tube body 11 in the optical axis direction.

A predetermined amount of buffer gas is supplied to the gas supply pipe 20 by a flow rate adjusting valve 25 and a flow meter 26 capable of adjusting the flow rate of buffer gas supplied from a buffer gas supply source (not shown) of the gas supply unit 3. Is done. The flow control valve 25 is an electromagnetic valve that can set an arbitrary opening degree by supplying a predetermined control current from a drive circuit (not shown), and the discharge gas control unit 6 controls the discharge tube main body. The flow rate of the buffer gas in 11 is controlled to be constant.

The gas exhaust pipe 21 is provided with a gas discharge portion 4 inside the discharge tube main body 11 for discharging a predetermined amount of discharge gas contributing to discharge in the discharge tube main body 11 toward a gas recovery device (not shown) of the gas exhaust portion 4. , A pressure gauge 27 for monitoring the pressure of the buffer gas, an exhaust pump 28 for discharging the discharge gas in the discharge tube 11 to a gas recovery device (not shown), and a pressure gauge 2.
A flow control valve 29 that is arranged between the pump 7 and the pump 28 and that controls the flow rate of the gas discharged by the pump 28 is connected. The flow control valve 29 is an electromagnetic valve that can set an arbitrary opening degree by supplying a predetermined control current from a drive circuit (not shown). It is set optimally by the discharge gas control unit 6 based on the signal.

The high-voltage power supply 5 applies a predetermined pulsed DC voltage between the anode 16 and the cathode 17 via the outer tube 15a and the electrode flange 18a and the outer tube 15b and the electrode flange 18b of the discharge tube body 11. Supply. The high-voltage power supply 5 is provided between the high-voltage power supply 5 and the outer cylinders 15a and 15b.
A discharge circuit, that is, a pulse voltage generating circuit 30 capable of applying the output of the above as a pulsed DC voltage having a predetermined rise time and repetition frequency between both outer cylinders, that is, between the anode 16 and the cathode 17, is connected. The rise time and voltage of the high-voltage pulse output from the pulse voltage generation circuit 30 can be set to, for example, approximately 10 by appropriately selecting the components of the pulse voltage generation circuit 30.
It is set so as to be tens of kV to tens of kV in ^-7 seconds or less. The repetition frequency is several kHz to several tens kHz.
z.

The initial discharge monitoring section 7 includes a photoelectric conversion element 31 and a video camera 35 near the outside of the output mirror 23 on the left side from the inside of the laser resonator, that is, the discharge tube main body 11. The photoelectric conversion element 31 and the video camera 35 are connected to the output mirror 23 and the Brewster tube 19 on the left side.
It is arranged so that the initial discharge state inside the discharge tube main body 11 can be optically detected through a. It is preferable that the photoelectric conversion element 31 and the video camera 35 are arranged so as to be slightly laterally deviated from the optical path of the output laser light.

In this way, the photoelectric conversion element 31 receives the initial discharge light from the discharge buffer gas inside the discharge tube main body, performs photoelectric conversion, and outputs an electric signal corresponding to the initial discharge state. Then, based on the output signal of the photoelectric conversion element 31,
It includes a judgment circuit 32 for judging the quality of the initial discharge, detects that the discharge efficiency has decreased due to the deterioration of the characteristics of the buffer gas in the discharge tube main body 11 or the like, and outputs the signal for the discharge via the main controller 8. A predetermined signal is output to the gas control unit 6 and the high-voltage power supply 5.

Next, the operation of the metal vapor laser device shown in FIG. 1 will be described.

First, the vacuum pump 28 of the gas exhaust unit 4
Is operated to evacuate the inside of the discharge tube main body 11, and thereafter, for example, neon gas (Ne) is injected into the discharge tube main body 11 as a discharge buffer gas from the gas supply pipe 20 of the gas supply unit 3. At this time, the discharge buffer gas (N
The pressure of the buffer gas in the discharge tube body 11 that has risen after e) is injected is measured by the pressure gauge 27. In addition,
The pressure of the buffer gas in the discharge tube main body 11 is set to a preset value determined by controlling the flow control valve 29 and the flow control valve 25 by the discharge gas control unit 6, that is, adjusting the gas discharge amount and the gas supply amount. Is done.

Next, the discharge circuit, that is, the pulse voltage generation circuit 30 is operated, and an excitation pulse voltage is applied between the cathode 17 and the anode 16, thereby generating an initial discharge plasma in the discharge tube body 11. With this plasma,
In the discharge tube main body 11, the vapor source metal 33 set in the discharge tube generates metal vapor, and the temperature is raised to a temperature required for laser oscillation. The temperature required for the laser oscillation is about 1,50 when the material of the vapor source metal 33 is, for example, copper.
0 ° C.

The metal vapor generated from the vapor source metal 33 is uniformly distributed in the discharge tube main body 11 thus heated and maintained at a substantially constant temperature. By continuing this state, free electrons in the plasma collide with the metal vapor to excite the metal vapor, and the inside of the discharge tube main body 11 eventually assumes a population inversion state. In this population inversion state, a laser beam is generated when the excited metal vapor transitions to a low energy level.

The laser light generated in the discharge tube main body 11 is
After passing through the windows 22a and 22b provided on the extension in the optical axis direction and being repeatedly reflected between the output mirror 23 and the total reflection mirror 24, the amplitude thereof is gradually increased. Output as an output laser beam.

By the way, in the metal vapor laser apparatus shown in FIG. 1, immediately after maintenance of the laser apparatus, for example, replenishment of the vapor source metal 33, or when restarting from a long term stoppage where air may enter. While the amount of metal vapor generated from the vapor source metal 33 by the initial discharge is raised to a temperature at which a stable discharge can be obtained, air adhering to a structural material such as the discharge tube body 11 and the heat insulating material 12 is removed. Moisture is released into the buffer gas. This raises the discharge resistance of the buffer gas in the discharge tube main body 11, so that the discharge characteristics deteriorate.

For this reason, immediately after maintenance or after a long stop, the exhaust pump 28 is operated to exhaust the inside of the discharge tube body 11, and after the exhaust, the discharge buffer gas is discharged from the gas supply pipe 20. There is a need to repeat the operation of injecting into the discharge tube body 11 and starting discharge again a required number of times.

Therefore, the deterioration of the discharge characteristics in the discharge tube main body 11, that is, the deterioration or fluctuation of the initial discharge, is sequentially monitored by the photoelectric conversion element 31 arranged so as to detect the change of the discharge state. Specifically, the initial discharge light emitted from the discharge tube main body is output by the photoelectric conversion element 31 as an electric signal corresponding to the intensity of the discharge light. The electric signal output from the photoelectric conversion element 31 is compared by a determination circuit 32 with a predetermined reference value.

By the way, as shown in FIG. 2, for example, as shown in FIG. 2, when the discharge characteristics due to the discharge buffer gas are deteriorated in the initial discharge, the light intensity of the output signal is shorter than that in the good condition. , The deterioration of the initial discharge in the discharge tube can be appropriately grasped. By feeding it back electrically or artificially, the initial discharge state is appropriately controlled.

Next, the photoelectric conversion element 31 and the judgment circuit 3
The operation of the discharge gas control unit 6 corresponding to the deterioration of the discharge characteristics in the discharge tube main body 11 detected by 2 will be described.

When the output of the photoelectric conversion element 31 corresponds to the fluctuation of the initial discharge of the light intensity as shown in FIG. 2, the judgment circuit 32 determines that the threshold level 34, which is the light intensity of a predetermined magnitude, is lower than the threshold level 34. When the output of the conversion element 31 falls, it is determined that the quality of the discharge gas in the discharge tube and the discharge characteristics have deteriorated. As shown in FIG. 2, since the number of changes per unit time of the signal output from the photoelectric conversion element 31 varies, the determination circuit 32
If the output of the photoelectric conversion element 31 continuously drops below the threshold level 34 for more than one minute, or if the fluctuation width exceeds a predetermined range, it is also determined that the discharge characteristics have deteriorated.

Hereinafter, the judgment circuit 32 determines that the discharge tube body 1
When it is determined that the initial discharge characteristics in 1 have deteriorated, the determination circuit 32 outputs a discharge stop request signal to the main controller 8. When the discharge stop request signal is output, the output of the high voltage power supply 5 and the output of the pulse voltage generation circuit 30 are cut off under the control of the main controller 8. Next, the main controller 8
, The opening degree of the flow control valve 29 of the gas exhaust unit 4 is increased and the exhaust pump 28
The discharge of the gas from the discharge tube body 11 is instructed, and the discharge gas is discharged from the discharge tube body 11. Subsequently, based on the control of the main controller 8, the discharge gas control unit 6 instructs the gas supply unit 3 to increase the opening degree of the flow control valve 25. Gas is supplied. The amount of the buffer gas supplied into the discharge tube main body 11, that is, the pressure of the buffer gas is, as described above, the gas exhaust unit 4 controlled by the discharge gas control unit 6.
Flow control valve 29 of the gas supply unit 3 and the flow control valve 25 of the gas supply unit 3
Is set to the optimum pressure.

As described above, the photoelectric conversion element 31 is arranged so that the discharge state due to the discharge buffer gas in the discharge tube main body can be detected, and based on the output thereof, the laser cavity 2, that is, the buffer gas in the discharge tube is discharged. By replacing the discharge characteristics each time the deterioration of the discharge characteristics is detected, the laser oscillation of the metal vapor laser device can be stabilized in a shorter time. As a result, automatic control can be performed in a shorter time, with higher accuracy, and as needed, as compared with conventional visual monitoring.

The buffer gas in the discharge tube main body corresponds to an instruction from the main controller 8 based on the result of detection of a change in light intensity, that is, a change in light intensity of discharge light generated therefrom by the photoelectric conversion element 31. Since the replacement is automatically performed under the control of the discharge gas control unit 6, it is necessary to monitor the deterioration of the initial discharge characteristics due to the deterioration of the discharge buffer gas in the discharge tube main body. The required personnel can be reduced. In addition, it is possible to keep the monitoring personnel away from the vicinity of the metal vapor laser device having a large energy, and it is possible to enhance the safety for the monitoring personnel.

The initial discharge monitoring unit 7 shown in FIG.
The monitoring may be performed by a monitor camera (video camera) 35 instead of the photoelectric conversion element 31 described above.
State or both may be operated simultaneously. In this case, the fluctuation of the output laser light output can be captured in a shorter time by monitoring the fluctuation of the light intensity of the output laser light visually by the management personnel in a monitoring room or a monitoring section (not shown).

The photoelectric conversion element 31 and the camera 35 may be fixed at a fixed position, or may be provided as a movable type as required for monitoring.

[0039]

As described above, according to the present invention, the state of the initial discharge caused by the buffer gas in the laser cavity, that is, the discharge tube body can be accurately detected in a short time.
It is possible to efficiently lead to stable metal vapor laser oscillation.

[Brief description of the drawings]

FIG. 1 is a schematic diagram showing a metal vapor laser device according to an embodiment of the present invention.

FIG. 2 is a graph showing a change in light intensity of output light of the metal vapor laser device shown in FIG.

FIG. 3 is a schematic diagram showing a conventional metal vapor laser device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Metal vapor laser device, 2 ... Laser resonator, 5 ... High voltage power supply device, 6 ... Discharge gas control part, 7 ... Initial discharge monitoring part, 11 ... Discharge tube Main unit, 16: anode, 17: cathode, 20: gas supply pipe, 21: gas exhaust pipe, 25: flow control valve (supply side), 28: exhaust pump, 29 ... Flow control valve (exhaust side), 30 ... Pulse voltage generation circuit, 31 ... Photoelectric conversion element, 32 ... Decision circuit, 33 ... Steam source metal, 35 ... Video camera.

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 5F071 AA03 BB05 HH01 HH02 HH09 JJ05 5F072 AA03 HH01 HH02 HH09 JJ05 JJ11 KK30

Claims (7)

[Claims] 1. A discharge source gas is held inside a discharge tube body, a discharge buffer gas having a predetermined pressure is introduced, an initial discharge is generated by applying a voltage, and the vapor source metal is vaporized and led to laser oscillation. In the metal vapor laser device, a photoelectric conversion element is arranged so as to be able to detect initial discharge light from the inside of the discharge tube main body due to the discharge buffer gas, and the photoelectric conversion element causes the discharge buffer gas inside the discharge tube main body to be detected. A metal vapor laser device characterized by detecting an initial discharge state and controlling the initial discharge state accordingly. 2. The metal vapor laser device according to claim 1, wherein the photoelectric conversion element detects a change in light intensity of the initial discharge light. 3. The metal vapor laser device according to claim 1, wherein the photoelectric conversion element detects a change in light intensity of the initial discharge light. 4. The metal vapor laser according to claim 1, wherein said photoelectric conversion element is provided on an upper side extending outward along an axial direction of said discharge tube main body. apparatus. 5. The apparatus according to claim 1, wherein the metal vapor laser device obtains a light intensity signal of the initial discharge light from the video signal while detecting a state of the initial discharge light output from the discharge tube main body with a video camera. Claim 1 to Claim 4
The metal vapor laser device according to any one of the above. 6. The metal-vapor laser apparatus stops the voltage application in response to an output signal output from the photoelectric conversion element, exhausts a discharge buffer gas from the discharge tube main body, and discharges the discharge tube gas from the discharge tube main body. 6. The metal vapor laser device according to claim 1, further comprising a control device capable of supplying a new discharge buffer gas therein. 7. The metal vapor laser device according to claim 6, wherein the discharge of the discharge buffer gas and the supply of a new discharge buffer gas are controlled by a solenoid valve.