JPH05283779A - Metal vapor laser device - Google Patents

Abstract

PURPOSE:To enable a metal vapor laser device to be easily operated by a method wherein the discharge stability of a metal vapor laser oscillation tube is judged basing on the second pulse current out of a first and a second pulse current flowing through a switching element at certain intervals, a discharge is stopped when it is found that the discharge is unstable, the oscillation tube is exhausted, and then a discharge is made to start again. CONSTITUTION:When a metal vapor laser oscillation tube 21 is made to start discharging, a first and a second pulse current flowing through a switching element 31 at certain intervals are detected by a control 38, and that discharge is stable or not is judged through the control 38 depending on signals obtained basing on a difference between a detected value and a set value. When the intervals of the pulse currents are larger than set values or the second pulse current is larger than the set value, discharge is judged to be unstable and stopped, and the laser oscillation tube 21 is exhausted through a feed-exhaust section 24. Thereafter, buffer gas is fed again, and the tube 21 is made to restart discharging. By this setup, a restarting operation is automatically repeated until discharge becomes stable, and a continuous observation can be dispensed with, so that a metal vapor laser device of this design can be easily operated.

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 that oscillates pulsed laser light.

[0002]

2. Description of the Related Art As is well known, laser light has been used in various fields from the past due to its excellent directivity and coherence. Recently, attention has been paid to the monochromaticity of laser light, and only the target substance is selectively excited by pulsed laser light, and its use for purification and removal of impurities is being promoted.

A metal vapor laser device, which is one of the laser devices used as described above, will be described below with reference to FIG. FIG. 5 is a connection diagram showing a schematic configuration.

In FIG. 5, reference numeral 1 denotes a metal vapor laser oscillator tube, inside of which a pair of electrodes 2 and 3 are arranged so as to face each other, and a gas supply device 6 is provided inside the air supply / exhaust unit 4 whose pressure is exhausted and reduced. The buffer gas is supplied from the valve via the valve 7. In the plasma formation region 8 between the electrodes 2 and 3, metal particles of a laser medium (not shown) are arranged.

On the other hand, 9 is a power supply unit, which is connected to the electrodes 2 and 3 to generate a discharge between them. That is, the power supply unit 9
A series circuit of the storage capacitor 10 and the high-speed switching element 11 is connected in parallel to the pair of electrodes 2 and 3, and the high-speed switching element 11 repeats the opening / closing operation according to the control signal from the pulse generator 12.

Further, in the series circuit of the storage capacitor 10 and the high speed switching element 11, a capacitor 13 and a resistor 1 are provided.
4 are connected in parallel, and a charging power supply 15 that charges the storage capacitor 10 in parallel is connected to the high-speed switching element 11. The charging power supply 15 includes a diode 16 and a resistor 17 connected in series,
It is connected in parallel.

In the conventional metal vapor laser device configured as described above, first, the inside of the metal vapor laser oscillator tube 1 is evacuated to a high vacuum state by the exhaust device 5, and then a buffer gas is predetermined from the gas supply device 6 therein. Supply so that the pressure becomes.

On the other hand, in the power source section 9, the high-speed switching element 11 is opened to charge the storage capacitor 10 by the charging power source 15 and closed to discharge the electric charge charged in the storage capacitor 10. A pulse voltage is applied to the electrodes 2 and 3. By applying the pulse voltage, discharge plasma is generated in the plasma formation region 8 between the electrodes 2 and 3, and the high-speed switching element 11 is repeatedly opened and closed, so that the storage capacitor 10 is repeatedly charged and discharged.

Along with this, the metal vapor laser oscillator tube 1
The electrodes 2 and 3 are repeatedly discharged, and the metal particles of the laser medium arranged in the plasma formation region 8 are heated and vaporized. Then, the metal vapor is excited by the electrons in the discharge plasma, the generated light is amplified by an optical resonator (not shown), and laser light is oscillated.

However, at the stage of performing repeated discharge between the electrodes 2 and 3 of the metal vapor laser oscillator tube 1, the discharge is not performed with time due to the cause of impurities mixed in the metal vapor laser oscillator tube 1. It often becomes stable and the discharge current decreases frequently. When the discharge becomes unstable in this way, the heating of the metal particles of the laser medium becomes insufficient, so that the laser medium may not vaporize or the metal vapor laser device may be damaged.

Therefore, in operating the metal vapor laser device, the state of the discharge in the metal vapor laser oscillator tube 1 is observed, for example, the size of the discharge plasma and the discharge current value, and the operation is performed when the discharge becomes unstable. Stop. Then, inside the metal vapor laser oscillation tube 1, the valve 7 is closed to stop the supply of the buffer gas, the gas is once exhausted by the exhaust device 5, and then the buffer gas is supplied again from the gas supply device 6. Restart the operation of. This operation is repeated until the discharge becomes stable.

As described above, when the metal vapor laser device is operated, the discharge condition must be constantly observed until the discharge becomes stable. When the discharge plasma is visually checked, the eyes are hurt by strong light. There is a problem that the judgment is delayed because the judgment criteria for whether the discharge is unstable are not objective.

Further, when the discharge becomes unstable,
The operation of stopping and restarting the operation of the metal vapor laser device had to be performed, and the operation was troublesome.

[0014]

As described above, in the conventional metal vapor laser device, it is necessary to observe the discharge state at all times during operation until the discharge is stabilized, which causes various problems and stable discharge is obtained. The driving operation up to the point was troublesome. The present invention has been made in view of such a situation, and an object thereof is to provide a metal vapor laser device that does not require observation of the discharge state and can be operated without a troublesome driving operation. ..

[0015]

SUMMARY OF THE INVENTION A metal vapor laser device according to the present invention comprises a metal vapor laser oscillator tube, a supply / exhaust section for exhausting the interior of the metal vapor laser oscillator tube to supply a buffer gas, and a metal vapor laser oscillator. Based on the detected signal and the power supply unit that repeatedly opens and closes the switching element between the electrodes of the tube to apply a pulse voltage to discharge between the electrodes of the metal vapor laser oscillation tube A first pulse current and a second pulse that flow at a time interval due to closing of the switching element in the control unit, and a control unit that controls the supply and discharge of the air supply and exhaust unit and controls the power supply unit. The electric current is detected, the stability of the discharge between the electrodes of the metal vapor laser oscillation tube is judged based on the signal obtained from the second pulse current, and when it is judged to be unstable, the control unit The discharge of the metal vapor laser oscillator tube is stopped, the inside is exhausted, and after the exhaust, the buffer gas is resupplied to the inside of the metal vapor laser oscillator tube by the air supply / exhaust section and the discharge of the metal vapor laser oscillator tube is restarted. It is characterized by having been made to do.

[0016]

In the metal vapor laser device configured as described above, the first pulse current and the second pulse current flowing through the switching element at time intervals when the metal vapor laser oscillator tube is discharged.
Of the pulse current of the second pulse current by the control unit, based on the signal of the time interval between the second pulse current and the first pulse current, or the difference between the current value of the second pulse current and the preset value. , The control unit determines the stability of the discharge of the metal vapor laser oscillation tube, the time interval is larger than a preset value,
Alternatively, when the current value of the second pulse current is smaller than a preset value, it is determined to be unstable, and in this case, the discharge of the metal vapor laser oscillation tube is stopped and the internal exhaust is performed in the air supply / exhaust section. After exhausting, the buffer gas is supplied again to restart the discharge of the metal vapor laser oscillation tube. Therefore, the starting operation is automatically repeated until the discharge is stabilized, it is not necessary to constantly observe the discharge situation, and the operation can be performed without any troublesome driving operation.

[0017]

Embodiments of the present invention will be described below with reference to the drawings.

First, the metal vapor laser device of the first embodiment will be described with reference to FIGS. FIG. 1 is a connection diagram showing a schematic configuration, and FIG. 2 is a diagram for explaining a pulse current flowing through a high speed switching element.

In the figure, a pair of electrodes 22 and 23 are arranged opposite to each other inside a metal vapor laser oscillation tube 21 formed in a substantially cylindrical shape with a predetermined interval. The inside of the metal vapor laser oscillation tube 21 is evacuated and depressurized by the exhaust device 25 of the air supply / exhaust section 24, and the depressurized inside is further supplied from the gas supply device 26 via the electromagnetic valve 27 to, for example, helium (He) or neon (Ne). ) Etc. buffer gas is supplied. The electrodes 22 and 23 facing each other
Metal particles of a laser medium (not shown), such as copper (Cu) or gold (Au), are arranged in the plasma formation region 28 between them.

On the other hand, the pair of electrodes 22 and 23 is connected to a power supply unit 29 for generating a discharge between them. That is, the storage capacitor 30 of the power supply unit 29
And a series circuit of high-speed switching elements 31 made of thyratron or the like connected in series to the pair of electrodes 22,
23 connected in parallel. The high-speed switching element 31 has a control terminal connected to a pulse generator 32 that outputs a control signal for repeating the opening / closing operation.

In the series circuit of the storage capacitor 30 and the high speed switching element 31, the waveform shaping capacitor 3 is provided.
3 and the charging resistor 34 are connected in parallel. Further, a charging power source 35 that charges the storage capacitor 30 in parallel is connected to both ends of the high speed switching element 31. A backflow prevention diode 36 and a resistor 37, which are connected in series, are connected in parallel to the charging power source 35.

A control unit 38 controls the operations of the air supply / exhaust unit 24 and the power supply unit 29. That is, the control unit 38 has a pulse detector 39 and a controller 40 to which the output signal thereof is input.
The opening / closing of the electromagnetic valve 27 of No. 4 and the operation of the charging power supply 35 are controlled.

The pulse detector 39 is provided on the terminal side of the high speed switching element 31 connected to one electrode 23 of the metal vapor laser oscillation tube 21, and the current detector 41 detects the current flowing through the high speed switching element 31. The output signal of is input. Further pulse detector 3
A signal synchronized with the control signal applied to the high speed switching element 31 is input to the pulse generator 9 from the pulse generator 32.

In the metal vapor laser device of this embodiment having the above-described structure, first, the inside of the metal vapor laser oscillator tube 21 is decompressed by the exhaust device 25 of the air supply / exhaust section 24 to a high vacuum state, and then exhaust is continued. On the other hand, by opening the electromagnetic valve 27 inside the metal vapor laser oscillation tube 21, the buffer gas made of, for example, helium is supplied from the gas supply device 26 so as to have a predetermined pressure.

On the other hand, in the power supply unit 29, the high speed switching element 31 is opened by the control signal from the pulse generator 32, and the storage capacitor 30 is charged by the charging power supply 35. Next, by changing the control signal of the pulse generator 32 and closing the high-speed switching element 31, the storage capacitor 3
The electric charge charged to 0 moves to the electrodes 22 and 23 of the metal vapor laser oscillation tube 21, and a pulse voltage is applied between the electrodes 22 and 23.

Discharge plasma is generated in the plasma formation region 28 between the electrodes 22 and 23 by applying the pulse voltage. Further, the application of the pulse voltage to both electrodes 22 and 23 is continuously performed by repeatedly outputting the control signal from the pulse generator 32, whereby the electrodes 22 and 2 are
The discharge for 3 is repeated.

When the high-speed switching element 31 is closed and the storage capacitor 30 is discharged, a pulse current flows through the high-speed switching element 31, this current is detected by the current detector 41, and its output signal is the pulse generator 32.
Is input to the pulse detector 39 together with a control signal for closing the high speed switching element 31 from.

The pulse current flowing through the high speed switching element 31 at this time is shown in FIG. 2 with the horizontal axis representing time and the vertical axis representing current. That is, the pulse generator 32
Control signal to close the high-speed switching element 31 which is output from and to the time T ₀ detected by the pulse detector 39, the first peak value of the pulse current P ₁ at time T ₁ is detected, also the time T _{At 2} , the second pulse current P ₂ having a smaller peak value than the first pulse current P ₁ is detected.

Further, the pulse detector 39 calculates the time interval ΔT _a (= T ₂ −T ₁ ) from the detection of the first pulse current P ₁ to the detection of the second pulse current P _2. And a comparison with a preset time interval ΔT _s is performed. The preset time interval ΔT _s is that the stability of the discharge between the electrodes 22 and 23 of the metal vapor laser oscillation tube 21 can be determined by the length of the time interval between the first pulse current and the second pulse current. The present inventors have obtained through experiments, and based on this, the discharge time is set within the range of stable time intervals.

When the comparison result of the time interval ΔT _a and the time interval ΔT _s is ΔT _s ≧ ΔT _a = T ₂ −T ₁ , it is assumed that the discharge is stable and the storage capacitor 30 is charged and discharged. The application of the pulse voltage to the electrodes 22 and 23 of the metal vapor laser oscillation tube 21 is repeated and repeated.

The temperature of the plasma forming region 28 rises up to about 1500 ° C. due to the repeated discharge between the electrodes 22 and 23, and the laser medium, for example, copper metal particles arranged therein is heated. Being vaporized.
Then, the metal vapor is excited by the electrons in the discharge plasma, the generated light is amplified by an optical resonator (not shown), and laser light is oscillated.

Further, as indicated by the broken line in FIG.
Of the pulse current P _'2 is slower time T from the time T _2' is detected at _2, the pulse detector 39 in the first pulse current P ₁
And the second pulse current P ′ ₂ with a time interval ΔT _b (= T ′
₂₋ T ₁ ) is calculated and a preset time interval ΔT _s
Is compared with.

If the comparison result of the time interval ΔT _b and the time interval ΔT _s is ΔT _s <ΔT _b = T ′ ₂ −T ₁ , it is judged that the discharge is unstable, and the judgment result is It is input to the controller 40.

Then, the controller 40 controls the charging power source 35.
And the discharge in the metal vapor laser oscillator tube 21 is stopped. At the same time, the electromagnetic valve 27 is closed by the control signal from the controller 40, and the supply of the buffer gas from the gas supply device 26 to the inside of the metal vapor laser oscillation tube 21 is stopped, but the exhaust device 25 continues to operate and the metal The inside of the vapor laser oscillation tube 21 is exhausted.

After the pressure inside the metal vapor laser oscillator tube 21 is reduced by the exhaust device 25 to a high vacuum state, the electromagnetic valve 27 is opened inside the metal vapor laser oscillator tube 21 again while continuing the exhaust to supply gas. The buffer gas is supplied from the device 26 to a predetermined pressure.

After the buffer gas is supplied, the power supply unit 29
Is operated again to charge and discharge the storage capacitor 30, and the pulse voltage is applied to the electrodes 22 and 23 of the metal vapor laser oscillation tube 21. And high-speed switching element 3
The pulse current flowing in 1 is detected, and the time intervals are similarly compared. While the discharge is determined to be unstable as a result of the time interval comparison, the control of the control unit 38 repeatedly stops the discharge of the metal vapor laser oscillation tube 21, exhausts the inside, and restarts the power supply unit 29.

When the discharge is judged to be stable as a result of the comparison of the time intervals, the charging and discharging of the storage capacitor 30 is continued and the pulse voltage is applied to the electrodes 22 and 23 of the metal vapor laser oscillation tube 21. This is repeated, and the discharge between the electrodes 22 and 23 is repeated. Then, the metal particles of the laser medium are heated and vaporized, the metal vapor is excited by the electrons, and the laser light is oscillated.

According to the present embodiment configured as described above, whether or not the discharge state between the electrodes 22 and 23 of the metal vapor laser oscillator tube 21 is stable is not accompanied by the operator's observation or the like. By detecting the pulse current flowing through the high-speed switching element 31, it can be surely detected. When the discharge is unstable, the discharge of the metal vapor laser oscillation tube 21 is repeatedly stopped and restarted automatically until the discharge becomes stable, and the troublesome operation is eliminated.

Further, the discharge is unstable, the operation is continued without vaporizing the laser medium, and the metal vapor laser device is not damaged.

Next, the metal vapor laser device of the second embodiment will be described with reference to FIGS. 3 and 4. FIG. 3 is a connection diagram showing a schematic configuration, and FIG. 4 is a diagram for explaining a pulse current flowing through the high speed switching element. The present embodiment is different from the first embodiment in the content of signal processing in the pulse detector, and the difference will be mainly described below.

In FIG. 3, a control unit 42 controls the operations of the air supply / exhaust unit 24 and the power supply unit 29. That is, the control unit 42 has a pulse detector 43 and a controller 40 to which an output signal thereof is input, and the controller 40 controls opening / closing of the electromagnetic valve 27 of the air supply / exhaust unit 24 and operation of the charging power supply 35. ..

The pulse detector 43 is provided on the terminal side of the high speed switching element 31 connected to one electrode 23 of the metal vapor laser oscillation tube 21, and the current detector 41 detects the current flowing through the high speed switching element 31. The output signal of is input. Further pulse detector 4
A signal synchronized with the control signal applied to the high speed switching element 31 is input to the pulse generator 3 from the pulse generator 32.

Then, as in the first embodiment, the high-speed switching element 31 is opened / closed by the control signal of the pulse generator 32, the storage capacitor 30 is charged / discharged, and the electrodes 22, 23 of the metal vapor laser oscillation tube 21 are charged. A pulse voltage is applied to. As a result, a discharge is generated between the electrodes 22 and 23. Further, the application of the pulse voltage to both electrodes 22, 23 is continuously performed by repeatedly outputting the control signal from the pulse generator 32, whereby the electrodes 22, 23 are
The discharge between is repeated.

In this operation, when the high-speed switching element 31 is closed and the storage capacitor 30 is discharged, a pulse current flows through the high-speed switching element 31, this current is detected by the current detector 41, and its output signal is output. But,
It is input from the pulse generator 32 to the pulse detector 43 together with a control signal for closing the high speed switching element 31.

At this time, the pulse current flowing through the high speed switching element 31 is shown in FIG. 4 with the horizontal axis representing time and the vertical axis representing current. That is, the pulse generator 32
The control signal for closing the high-speed switching element 31 output from the pulse detector 43 detects the peak value of the first pulse current P ₁ at time T ₁ with respect to the time T ₀ detected by the pulse detector 43. _{At 2} , the peak value of the _second pulse current P ₂ having a smaller current value than the first pulse current P ₁ is detected.

In the pulse detector 43, the second pulse detected at time T ₂ after the first pulse current P ₁ is detected.
The average current value I ₂ of the pulse current P ₂ is measured, and the average current value I ₂ is compared with the preset current value I _s . It should be noted that the average current value I ₂ is measured as needed by measuring the current value of the second pulse current P ₂ of the pulse current flowing through the high-speed switching element 31 repeatedly as needed for accuracy.
Sampling is performed a predetermined number of times or more, and this is averaged.

Further, the preset current value I _s is such that the stability of the discharge between the electrodes 22 and 23 of the metal vapor laser oscillation tube 21 is the time T of the first pulse current and the second pulse current. _The present inventors have obtained by experiments that it can be determined by the magnitude of the current value of the second pulse current detected in 2 and based on this, the discharge current is set within the range of stable current values.

Then, the average current value I ₂ of the second pulse current P ₂ at the pulse detector 43 and the preset current value I _{2
When the} result of comparison with _s is I ₂ ≧ I _s , it is assumed that the discharge is performed stably, and the charge and discharge of the storage capacitor 30 is continued, and a pulse is applied to the electrodes 22 and 23 of the metal vapor laser oscillation tube 21. The voltage application is repeated.

By repeatedly performing the discharge between the electrodes 22 and 23, the temperature of the plasma forming region 28 is reduced to about 1.
The laser medium, which has been raised to 500 degrees and is placed there,
For example, metal particles of copper are heated and vaporized. Then, the metal vapor is excited by the electrons in the discharge plasma, the generated light is amplified by an optical resonator (not shown), and laser light is oscillated.

[0050] Also, it measured ₂ 'average current value I detected by the _second time T _2' of the pulse detector 43 second pulse current P shown by a broken line in FIG. 4 is an average current value I _'2 When the comparison result with the preset current value I _s is I ₂ <I _s, it is determined that the discharge is unstable, and the determination result is input to the controller 40.

Then, as in the first embodiment, the controller 4
The operation of the charging power supply 35 is stopped by 0, and the discharge in the metal vapor laser oscillation tube 21 is stopped. Controller 4 at the same time
The electromagnetic valve 27 is closed by the control signal from 0, and the supply of the buffer gas from the gas supply device 26 to the inside of the metal vapor laser oscillation pipe 21 is stopped, but the exhaust device 25 continues to operate and the metal vapor laser oscillation is performed. The inside of the pipe 21 is exhausted.

Gas is supplied by opening the electromagnetic valve 27 inside the metal vapor laser oscillation tube 21 again while continuing evacuation after decompressing the inside of the metal vapor laser oscillation tube 21 by the exhaust device 25 to make a high vacuum state. The buffer gas is supplied from the device 26 to a predetermined pressure.

After the buffer gas is supplied, the power supply unit 29
Is operated again to charge and discharge the storage capacitor 30, and the pulse voltage is applied to the electrodes 22 and 23 of the metal vapor laser oscillation tube 21. And high-speed switching element 3
The pulse current flowing in 1 is detected, and the current values are similarly compared. While the discharge is determined to be unstable based on the comparison result of the current values, the control of the control unit 42 repeatedly stops the discharge of the metal vapor laser oscillation tube 21, exhausts the inside, and restarts the power supply unit 29.

If it is judged from the comparison result of the current values that the discharge is stable, the charging and discharging of the storage capacitor 30 is continued, and the pulse voltage is applied to the electrodes 22 and 23 of the metal vapor laser oscillation tube 21. This is repeated, and the discharge between the electrodes 22 and 23 is repeated. Then, the metal particles of the laser medium are heated and vaporized, the metal vapor is excited by the electrons, and the laser light is oscillated.

In this embodiment having the above-mentioned structure, the same operation and effect as those of the first embodiment can be obtained.

The present invention is not limited to the above-mentioned embodiments, but can be implemented with various modifications without departing from the scope of the invention.

[0057]

As is apparent from the above description, the present invention provides a signal obtained from the second pulse current of the first pulse current and the second pulse current flowing through the switching element at time intervals. The stability of the discharge of the metal vapor laser oscillation tube is judged based on the above, and if it is unstable, the discharge is stopped and the inside is evacuated, and the discharge of the metal vapor laser oscillation tube is restarted after the evacuation. As a result, it is possible to obtain an effect such that it is not necessary to observe the discharge state, and the vehicle can be driven without any troublesome driving operation.

[Brief description of drawings]

FIG. 1 is a connection diagram showing a schematic configuration of a first embodiment of the present invention.

FIG. 2 is a diagram for explaining a pulse current flowing through the high speed switching element in the above.

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

FIG. 4 is a diagram for explaining a pulse current flowing through the high speed switching element in the above.

FIG. 5 is a connection diagram showing a schematic configuration of a conventional example.

[Explanation of symbols]

 21 ... Metal vapor laser oscillation tube 22, 23 ... Electrode 24 ... Air supply / exhaust part 25 ... Exhaust device 26 ... Gas supply device 29 ... Power supply part 30 ... Storage capacitor 31 ... High speed switching element 38 ... Control part 39 ... Pulse detector 40 ... Controller

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Yasushi Iseki No. 1 Komukai Toshiba-cho, Saiwai-ku, Kawasaki-shi, Kanagawa Inside the Toshiba Research Institute, Inc. (72) Inventor Setsuo Suzuki Komukai-Toshiba, Kawasaki-shi, Kanagawa No. 1 Incorporated company Toshiba Research Institute

Claims (1)

[Claims] 1. A switching element is repeatedly opened and closed between a metal vapor laser oscillation tube, a supply / exhaust part for exhausting the inside of the metal vapor laser oscillation tube to supply a buffer gas, and an electrode of the metal vapor laser oscillation tube. A power supply unit for applying a pulse voltage to cause a discharge between the electrodes of the metal vapor laser oscillation tube, a current flowing through the switching element is detected, and supply / discharge of the air supply / exhaust unit is controlled based on the detected signal. A control unit for controlling the power supply unit, wherein the control unit detects a first pulse current and a second pulse current flowing at a time interval by closing the switching element, and detects the second pulse current. The stability of the discharge between the electrodes of the metal vapor laser oscillation tube is judged based on the signal obtained from the pulse current, and when it is judged that the discharge is unstable, the control unit emits the metal vapor laser. The discharge of the vibrating tube is stopped to evacuate the interior, and after the evacuation, the buffer gas is resupplied to the inside of the metal vapor laser oscillating tube by the air supply / exhaust section to restart the discharge of the metal vapor laser oscillating tube. A metal vapor laser device characterized by the above.