JPH1093202A - Metal vapor laser apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a stable laser output at low cost by providing a means for controlling pure neon gas flow rate and pure hydrogen gas flow rate regulate the mixing ratio, and a means for measuring the pressure of discharging gas to individually control the pure neon gas flow rate and the pure hydrogen gas flow rate in a discharge gas introducing system. SOLUTION: The metal vapor laser apparatus comprises a pressure gage 18 for measuring discharge gas pressure in a discharge tube 5. A flow-regulating valve 19 and an automatic regulating valve 26 are sequentially connected to an exhaust tube for connecting the tube 5 to a vacuum exhaust pump 20. Further, the apparatus also comprises a controller 27 for operating the valve 26, according to a signal from the gage 18 to control discharge gas pressure in the tube 5. The apparatus also comprises a discharge gas controller 33 for controlling the flow rates of a hydrogen gas-flow measuring regulating valve 30 and a neon gas flow-measuring regulating valve 32 according to a signal from the controller 27.

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 apparatus, and more particularly to a means for controlling a mixture ratio of a neon gas and a hydrogen gas in a discharge buffer gas (hereinafter abbreviated as a discharge gas) filled in a discharge tube.

[0002]

2. Description of the Related Art A conventional general metal vapor laser device is:
For example, it is configured as shown in FIG. That is, in the figure, an anode 3 and a cathode 4 are connected to both ends of a cylindrical ceramic tube 2 in which a plurality of metal vapor sources 1 are installed inside via a joining member 2a, thereby forming a discharge tube 5. ing. Each of the anode 3 and the cathode 4 of the discharge tube 5 is provided with an electrode flange 6. The electrode flange 6 includes a body 7 surrounding the discharge tube 5 and an electrode support flange 10 interposed between the insulating tube 8 and the Brewster tube 9.
It is mounted and fixed. Each electrode of the anode 3 and the cathode 4 is fixed to an electrode support flange 10 via an electrode flange 6. The outer peripheral surface of the discharge tube 5 is surrounded by a heat insulating material 11, and the outside of the heat insulating material 11 is a body 7 and an insulating tube flange 1.
2 covered with an insulating tube 8. A pair of Brewster tubes 9 are connected to each of the electrode support flanges 10.
The output mirror 14 is provided outside these windows 13.
And a total reflection mirror 15 are arranged to form a resonator.

In FIG. 3, a gas supply pipe 16 for supplying, for example, a neon (Ne) gas as a discharge gas is connected to a blaster pipe 9 shown on the left side, and a gas exhaust pipe is connected to the blaster pipe 9 shown on the right side. Tube 17 is connected. The gas exhaust pipe 17 is provided with a pressure gauge 18 on the way, and is connected to a vacuum exhaust pump 20 via a flow control valve 19. A DC high voltage is applied between the left electrode support flange 10 and the insulating tube flange 12.

In FIG. 1, reference numeral 21 denotes a charging capacitor, 22 denotes an intermediate capacitor, 23 denotes a resistor, 24 denotes a thyratron, and 25 denotes a diode. In the metal vapor laser device having the above configuration, the laser oscillates as follows. First, a discharge gas, for example, a neon gas, is supplied into the discharge tube 5 from the gas supply tube 16. Next, a high voltage is applied between the anode 3 and the cathode 4 to form a discharge plasma. Then, the ceramic tube 2 is heated to a high temperature by the discharge plasma, and the metal vapor source 1 generates vaporized metal particles serving as a laser medium, for example, copper vapor. Further, the copper vapor diffuses into the ceramic tube 2 and is excited by free electrons in the discharge plasma in the ceramic tube 2. When the excited copper vapor transitions to a low energy level, it emits laser light.

As described above, laser oscillation is performed by forming a plasma by discharging a high voltage into a discharge gas.
The discharge resistance at the time of this discharge varies depending on the generated copper vapor, and in order to change the laser output, a discharge gas obtained by mixing about 0.5 to 2% of hydrogen gas with neon gas is used as the discharge gas. However, since the discharge resistance changes depending on the concentration of the hydrogen gas, it is necessary to keep the mixed gas ratio constant.

For this reason, a discharge gas to be supplied to the laser apparatus uses a mixed gas cylinder previously mixed at a predetermined concentration. Further, at the start of discharge having a large discharge resistance, switching is performed using a valve in order to use only pure neon gas.

Here, at the start of operation of the laser device, the temperature of components such as the discharge tube 5 is at room temperature, and the temperature is raised to a high temperature during laser oscillation operation to generate metal vapor. It is known that the laser energy decreases, the discharge energy decreases, and the laser output decreases. At present, as a countermeasure, a method of mixing a small amount (0.1 to 2%) of hydrogen gas with a discharge gas is used. Therefore, an operation is performed in which the discharge gas is switched between pure neon gas and a mixed gas depending on the operation state.

[0008]

However, a laser device is generally used in combination with a large number of devices, and a large amount of expensive mixed gas is required. Further, it is necessary to switch the discharge gas from pure neon gas to a mixed gas of neon gas and hydrogen gas depending on the state of the laser device. As shown in FIG. 4, it takes a long time for the mixture ratio in the discharge tube 5 having a certain capacity to reach a predetermined value when switching to the mixed gas. This change in the mixing ratio is a problem because it causes a change in the laser output. SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and has as its object to provide a metal vapor laser device capable of obtaining a stable laser output at low cost.

[0009]

In order to achieve the above object, a metal vapor laser device according to the present invention is provided with a metal vapor source for generating a metal vapor inside, and discharges the inside of a discharge tube filled with a discharge gas. In a metal vapor laser device that generates laser light by heating, a discharge tube and two gas supply pipes for injecting discharge gas into the discharge tube are installed, and one system is a pure neon gas supply pipe provided with a device for controlling the flow rate. The other system is a hydrogen gas supply pipe provided with a device for controlling the flow rate, and further includes a measuring device for measuring the discharge gas pressure, a system for supplying the discharge gas by the discharge gas pressure, and a control means for controlling the flow rate. Things.

According to the present invention having the above structure, when the discharge resistance in the discharge tube at the start of discharge is large, pure neon gas is supplied to easily start discharge. Next, when the discharge tube temperature rises and the discharge resistance decreases, pure hydrogen gas or pure neon gas and hydrogen gas whose flow rates have been adjusted to increase the mixture ratio of hydrogen gas are supplied, and the mixture ratio in the discharge tube is increased. Is changed to a predetermined value in a short time. After the mixture ratio in the discharge tube reaches a predetermined concentration, each flow rate is controlled such that the mixture ratio of pure neon gas and hydrogen gas becomes a predetermined mixture ratio.
As described above, the discharge gas condition suitable for the operation condition of the laser device can be set using the pure neon gas and the hydrogen gas, and the laser output can be oscillated stably.

[0011]

An embodiment of the present invention will be described below in detail with reference to the drawings. The metal vapor laser device according to the present invention is constructed as shown in FIG. 1, and the same or corresponding parts as those in the conventional example (FIG. 3) will be described using the same reference numerals.

In FIG. 1, an anode 3 and a cathode 4 are connected to opposite ends of a ceramic tube 2 via a joining member 2a. Pulse discharge is performed at the anode 3 and the cathode 4. A heat insulating material 11 is provided on the outer periphery of the ceramic tube 2.
And a metal body 7 and an insulating tube 8 are arranged on the outer periphery thereof. A pair of Brewster tubes 9 are connected to the anode 3 and the cathode 4. The left blaster pipe 9 has a gas supply pipe 1 connected to a gas supply system.
6 and a discharge gas exhaust pipe 17 are connected to the blaster pipe 9 on the right side, respectively. In the gas supply pipe 16,
A hydrogen gas flow measurement and adjustment valve 30 connected to a hydrogen gas supply pipe 29 through a gate valve 28 with a gas supply system and a neon gas flow measurement and adjustment valve 32 connected to a neon gas supply pipe 31 are provided side by side.

A pressure gauge 18 for measuring the discharge gas pressure in the discharge tube 5 is provided, and a gas exhaust pipe connecting the discharge tube 5 and the vacuum exhaust pump 20 has a flow control valve 19 and an automatic adjustment. The valves 26 are sequentially connected. Further, the automatic adjustment valve 26 is operated by a signal from the pressure gauge 18,
Thus, a controller 27 for controlling the discharge gas pressure in the discharge tube 5 is provided. A discharge gas control device 33 that controls the flow rates of the hydrogen gas flow rate measurement adjustment valve 30 and the neon gas flow rate measurement adjustment valve 32 based on a signal from the controller 27.
Is provided. The gas supply pipe 16 supplies a discharge gas such as neon gas into the discharge tube 5, and the gas exhaust pipe 17 discharges the discharge gas or the like inside the discharge tube 5 to the outside. On the outside of the window 13 of the Brewster tube 9, an output mirror 14 and a total reflection mirror 15 are arranged, respectively, thereby constituting a laser resonator.

The above-described pulsed two-pole discharge is performed by the electrode support flange 1 which supports the anode 3 and the cathode 4 and allows current to flow therethrough.
This is done by a pulse high voltage power supply connected to zero. The pulse high-voltage power supply includes a charging capacitor 21, an intermediate capacitor 2
2, resistor 23, thyratron 24 and diode 25
And the like. This pulse high-voltage power supply has a structure in which the charge charged in the charging capacitor 21 is:
By firing the thyratron 24, a discharge current is generated with a rise time of approximately 10 ^-7 seconds or less. The thyratron 24 is a pulse discharge switching element. The pulse high voltage to be generated
KV to several tens KV, and the repetition frequency is several kHz to several tens KHz.

The symbol A in the figure is an anode terminal,
K is a cathode terminal, and G is a trigger signal introduction terminal. The other configuration is the same as that of FIG. 3, and the description thereof is omitted.

Next, the operation of the embodiment will be described. First, the vacuum pump 20 is operated to evacuate the discharge tube 5. After the evacuation, as shown in FIG. 2, the hydrogen gas flow rate measurement adjustment valve 30 is closed from the gas supply pipe 16 so that the flow rate becomes 0, and the discharge rate is controlled by the neon gas flow rate measurement adjustment valve 32 to a predetermined flow rate. Inject into 5. At this time, the gas pressure in the discharge tube 5 increased by the discharge gas injection is measured by the pressure gauge 18. The controller 27 operates the automatic control valve 26 so that the measured value becomes a preset pressure value, the discharge amount of the discharge gas is adjusted, and the pressure in the discharge tube 5 is controlled to the set value.

Next, the pulse high voltage power supply is operated to generate plasma in the ceramic tube 2, and the plasma is heated to a temperature at which the metal vapor source 1 can generate metal vapor. The temperature required for laser oscillation is, for example, about 1500 ° C. when the metal vapor source 1 is copper. By maintaining this state, the metal vapor is uniformly distributed in the ceramic tube 2.

Free electrons in the plasma collide with the metal vapor to excite the metal vapor, and eventually the inside of the ceramic tube 2 has a population inversion. In this state, laser light is generated when the excited metal vapor transitions to a low energy level. The laser light generated in the ceramic tube 2 passes through the window 13 and its amplitude increases and powers up while being reflected by the output mirror 23 and the total reflection mirror 15 constituting the laser resonator. The extracted laser light is output.

However, it is known that the laser output decreases because the electric resistance during discharge decreases due to the generation of metal vapor and the discharge energy decreases. At present, as a countermeasure, a small amount of hydrogen gas (0.1 to 2%) is used as the discharge gas.
A method of mixing is used. In order to change the hydrogen mixture ratio in the discharge gas in a short time, first, the neon gas flow rate measurement adjustment valve 32 is closed so that the flow rate becomes 0,
Hydrogen gas is injected into the discharge tube 5 by the hydrogen gas flow measurement adjusting valve 30 by the discharge gas control device 33 until the measured value of the pressure gauge 18 reaches a preset pressure. Next, the neon gas flow measurement adjustment valve 32 and the hydrogen gas flow measurement adjustment valve 3
Control is performed so that 0 becomes a predetermined mixing ratio.

As described above, according to this embodiment, the mixing ratio of the neon gas and the hydrogen gas as the discharge gas can be set in a short time, so that a stable laser output can be obtained. Further, since two types of neon gas and hydrogen gas are used as the discharge gas, the cost is lower than that of the mixed gas.

(Other Embodiments) As another embodiment, first, the neon gas flow rate measurement adjustment valve 32 and the hydrogen gas flow rate adjustment valve 30 are adjusted to inject a predetermined mixture ratio to the set discharge gas pressure. It is also possible to adopt an operation system in which the flow rate of the hydrogen gas is closed at the start of discharge, only neon gas is injected, and the discharge resistance at the start of discharge is reduced.

[0022]

As described above, according to the present invention,
It is possible to change the hydrogen gas mixture ratio of the discharge gas in the discharge tube in a short time, and it is possible to obtain a stable laser output. Further, since hydrogen gas is mixed with neon gas at a flow ratio when used, it can be constructed at a lower cost than in the case of using a gas mixed in advance.

[Brief description of the drawings]

FIG. 1 shows a metal vapor laser according to an embodiment of the present invention.
FIG. 2 is a circuit configuration diagram including a cross-sectional view illustrating the device.

FIG. 2 is a graph illustrating a change over time in a discharge gas pressure and a mixture ratio of a neon gas and a hydrogen gas during operation of the metal vapor laser device of the present invention.

FIG. 3 is a circuit diagram including a sectional view showing a conventional metal vapor laser device.

FIG. 4 is a graph illustrating a change over time in a discharge gas pressure and a mixture ratio of a neon gas and a hydrogen gas during operation in a conventional metal vapor laser device.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Metal vapor source, 5 ... Discharge tube, 16 ... Gas supply tube, 17
... gas exhaust pipe, 18 ... pressure gauge, 19 ... flow control valve, 27
... Controller, 28 ... Gate valve, 29 ... Hydrogen gas supply pipe, 30
... Hydrogen gas flow measurement adjusting valve, 31 ... Neon gas supply pipe,
32: a neon gas flow measurement adjusting valve; 33: a discharge gas control device.

Claims (2)

[Claims] 1. A metal vapor laser device in which a metal vapor source for generating metal vapor is provided and a discharge tube filled with a discharge gas is heated by discharge to generate laser light. A means for controlling the flow rate of pure neon gas and the flow rate of pure hydrogen gas to adjust the mixing ratio thereof. 2. The metal vapor laser according to claim 1, further comprising a controller for measuring the pressure of the discharge gas and individually controlling the flow rates of the pure neon gas and the pure hydrogen gas. The equipment.