JPH05299742A - Gas laser oscillator - Google Patents

Abstract

PURPOSE:To obtain a gas laser oscillator wherein its power-supply capacity and its power-supply efficiency are enhanced, its overall efficiency is high and it is compact by a method wherein an AC power supply whose discharge frequency is 700kHz or higher is used, discharge electric power is fed into a region which is effective in exciting a laser and a solid-state-element switching power supply whose power-suply capacity is large is used. CONSTITUTION:Electric power from 200V at three phases is passed through a DC power supply 12; high-frequency electric power whose frequency is 700kHz or higher is generated by means of an inverter part 13; after that, the power supply is fed to electrodes 4a, 4b through a matching device 14. The DC power- supply part is constituted of a circuit which rectifies and smoothes 200V AC and of a pulse-width modulation-type DC conversion circuit; it controls the level and the phase of the output high-frequency power supply which is supplied to the electrodes 4a, 4b. The inverter part 13 is constituted of a static induction transistor; it performs a switching operation; it monitors an output voltage waveform and an output current waveform from the inverter part; it changes a frequency. Thereby, it makes the phase of both waveforms definite and performs a PLL control operation so as to always keep a matching state.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a gas laser oscillator that oscillates laser light by applying an AC voltage between electrodes.

[0002]

2. Description of the Related Art FIG. 5 shows an example of a conventional structure of a gas laser oscillator of this type. In this configuration, the gas flow is orthogonal to the optical axis,
This is an example of a so-called cross-flow laser.

In FIG. 1, an external wind tunnel 1 having a rectangular cross section is provided with an internal wind tunnel 2 made of stainless steel, iron or aluminum and having a substantially U-shaped cross section. In the center of the upper surface of the external wind tunnel 1, a flat plate-shaped first member made of ceramics or the like is provided.
The dielectric 3a is opposed to the dielectric 3b at a predetermined interval and is hermetically attached. The inner wind tunnel 2 is closed by a dielectric 3b, and the inner wind tunnel 2 communicates with the outside air. Further, the first electrode 4a is attached to the central portion of the upper surface of the first dielectric 3a to form one dielectric electrode, and the second electrode
A second electrode 4b forming a pair with the first electrode 4a is attached to the central portion of the lower surface of the dielectric 3b, and constitutes the other dielectric electrode.

The first electrode 4a and the second electrode 4b are connected to an AC power supply 5. A gas serving as a laser medium is enclosed in a space between the outer wind tunnel 1 and the inner wind tunnel 2, and the gas is blown inside the outer wind tunnel 1 by an air blower 6 arranged below the inner wind tunnel 2. It is circulated in the A direction and cooled by the heat exchanger 7.

In the above structure, the first
When an AC voltage is applied between the first and second discharge electrodes 4a and 4b, an AC discharge is generated between them via the first and second dielectrics 3a and 3b, and the first and second dielectrics 3a, 3
The gas flowing between b is excited and the laser light 8 is generated in the direction perpendicular to the paper surface.

Here, as the element for the AC power supply 5, a vacuum tube is used when the oscillation frequency is high (for example, 13.56 MHz), and a solid element is used when the oscillation frequency is low (for example, 100 kHz).

[0007]

However, the conventional laser device having the above-mentioned structure has the following problems to be solved.

When the frequency is increased in order to increase the laser oscillation efficiency (the conversion efficiency from the discharge input to the laser output), a vacuum tube type power supply is used, and the power supply efficiency (the conversion efficiency from 200 V AC power to high frequency power) is class C. Up to 70 even with amplification method
%, Actually 55%. As a result, the overall efficiency of the laser oscillator (exchange efficiency from 200 V AC power to laser output) cannot be increased. Further, since the vacuum tube type power supply is used, the size of the power supply itself becomes large.

On the contrary, the power efficiency is increased (up to about 90%),
If a low frequency discharge (100 kHz) is performed using a solid-state element to reduce the power supply, the laser oscillation efficiency will decrease, so that the overall efficiency of the laser oscillator will not increase. Further, since the frequency is low, the laser pulse characteristic is also deteriorated.

Therefore, the present invention has been made in consideration of the above points, and an object thereof is to provide a gas laser oscillator which is small in size, high in total efficiency, and excellent in laser pulse characteristics.

[0011]

As a means for achieving the above object, the present invention provides a container whose inside is filled with a gas which is a laser medium, at least a pair of discharge electrodes provided facing each other, and It is connected to an AC power supply for applying an AC voltage, the frequency of the AC power supply is 700 kHz or more, a solid-state element is used for the AC power supply to perform switching operation, and the high frequency power output per unit is 4
A gas laser oscillator having a power of kW or more is provided.

[0012]

The physical structure of the discharge is largely composed of the positive column 9 and the electrode layer 10 near the electrode, as shown in FIG. Sun Pillar 9
The injected power contributes to the laser excitation, but
The power injected into the laser does not contribute to laser excitation. When the AC discharge frequency is low, the displacement current is the main component of the current flowing inside the electrode layer 10, and the power loss is small. However, when the AC discharge frequency is low, the conduction current component is added to the displacement current component of the current flowing inside the electrode layer 10, resulting in power loss. When the AC discharge frequency is sufficiently low, the current flowing inside the electrode layer 10 has only a conduction current component, resulting in a large power loss. In addition, since the switching operation is performed using the solid-state element having a large power output capacity, high power efficiency can be obtained.

Therefore, by increasing the frequency of the AC power supply, the power loss in the region of the electrode layer 10 can be reduced, and since the solid-state switching power supply that can increase the power supply capacity is used, the power supply efficiency is also increased. A laser oscillator with high overall efficiency can be realized.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIGS. The description of the same parts as those of the conventional example will be omitted. FIG. 1 shows an example of a gas laser oscillator according to the present invention, in which an AC power supply (700 kHz or higher) 11 is different from the conventional one.

FIG. 2 is a diagram showing an outline of the AC power supply 11. Electric power from the three-phase 200 V is supplied to the electrodes 4a and 4b through the matching unit 14 after generating high frequency power of 700 kHz or more in the inverter unit 13 through the DC power supply unit 12.
The DC power supply unit is composed of a circuit for rectifying and smoothing AC200V and a pulse width modulation (PWM) type DC conversion circuit, and controls the level of output high frequency power supplied to the electrodes 4a and 4b and pulse control. The inverter section 13 is composed of a static induction transistor (SIT) as an element and performs a switching operation.

By the way, although not shown in the figure, by varying the frequency by monitoring the output voltage waveform and the output current waveform from the inverter section, even if the discharge load fluctuates while keeping the phase of both waveforms constant. PLL that always maintains a consistent state
(Phase Locked Loop) control is performed. Thereby, it is possible to efficiently inject the high frequency power into the discharge load. Also, in order to keep the output high-frequency power constant, the output current and voltage from the inverter section are monitored to monitor the DC power supply section.
Feedback control by sending to 12 is also performed. The operation of the laser device of this embodiment having such a configuration will be described below.

FIG. 3 shows the CO of this embodiment obtained by the experiment.
Figure ₂ shows the relationship between the discharge frequency and the loss in the electrode layer region for _two lasers. In the figure, the displacement current component is a constant value j ₀ (mA / c
m ² ).

According to FIG. 3, when the discharge frequency is 100 kHz, only the conduction current flows in the electrode layer region, and the loss in this region is 100%. At 100 kHz, the electrode gap width
If it is about 15 mm, the ratio of high frequency power injected into the positive column and the electrode layer region is about 70% and 30%, which is 70% of the discharge input.
Only% contributes to laser excitation. However, the discharge frequency
At 700 kHz or higher, a lossless displacement current flows in the electrode layer region, and there is no loss in this region, which can contribute to laser excitation. When the discharge frequency exceeds 10 MHz, almost 100% of the discharge input contributes to laser excitation.

Therefore, the laser excitation efficiency is increased by setting the discharge frequency to 700 kHz or higher. That is, the laser oscillation efficiency (laser output / discharge input) can be increased. Further, since the discharge frequency is high, the laser pulse characteristic is also improved. Next, in order to reduce the size of the AC power supply and increase the power supply efficiency, it is necessary to perform switching operation using solid-state elements.

Conventionally, a power MOS FE has been used as a solid-state element.
Although T has been used, one of the devices that satisfy the above discharge frequency
Since the power capacity per unit is small, it is necessary to use 10 or more elements in one arm in the bridge circuit when trying to perform switching operation, and measures to eliminate the variation in operation between each element is necessary. .. As a result, the bridge circuit becomes complicated and large. Moreover, even if many elements are used, the output of the power supply (during CW operation) is per unit,
It is about 1-2 kW at most.

As a power source for the laser, it is preferable to reduce the number of divisions as much as possible and supply power to the electrodes in order to improve the pulse control characteristics of the laser. In particular, in the transverse flow laser, if the number of divided electrodes is increased, the distance between the electrodes must be taken in order to suppress abnormal discharge between the divided electrodes, and the laser device becomes large accordingly and the efficiency also decreases. Therefore, it is desirable to configure the power source with one unit and supply it to the electrodes.

In general, a processing CO ₂ laser having a laser output of 500 W or more is often used. Since the laser oscillation efficiency is about 12.5%, at least 1 unit of 4 kW (CW operation or average output) is required as the power supply capacity. This capacitance is a value that cannot be obtained using a power MOSFET.

In this embodiment using the static induction transistor (SIT), an output of 4 kW or more is possible by placing one or two elements in each arm of the bridge circuit.

Therefore, if 10 pieces are arranged in each arm of the bridge circuit, it is possible to obtain an output of about 40 kW or more. In addition, SIT is suitable as a gas laser discharge element because of its excellent surge resistance.

As described above, according to this embodiment, it is possible to reduce the loss in the electrode layer region by setting the discharge frequency to 700 kHz or more, and to perform the switching operation using the large capacity solid state element. As a result, a small gas laser oscillator having high overall efficiency and good pulse performance can be obtained.

The present invention is not limited to the above-mentioned embodiment, but may be an axial flow type laser heat conduction cooling type laser. In this case, by supplying high-frequency power to a plurality of discharge tubes from the power supply of one unit, it is possible to obtain laser light with excellent pulse characteristics.

When high frequency power is supplied to the pair of electrodes by one unit of AC power supply, one unit of power supply may be composed of a plurality of subunits. That is, each sub-unit has one inverter circuit, and a high-capacity solid-state element is used in the bridge circuit. For example, if the high frequency output of each subunit is 20 kW, the AC power output of one unit composed of four subunits is 80 kW, which is a very high frequency output. Furthermore, in this embodiment, as a high-speed, high-capacity solid-state element, especially an electrostatic induction type transistor (SI
Although T) is used, other high speed, high capacity solid state elements may be used.

Finally, although the present embodiment describes the gas laser oscillator, the same performance can be obtained by applying it to a laser amplifier, and it can also be applied to other gas lasers such as an excimer laser.

[0029]

As described above, according to the present invention,
Since the discharge power can be injected into the effective region for laser excitation by dispersing an AC power supply with a discharge frequency of 700 kHz or more, a solid-state switching power supply that can increase the laser oscillation efficiency and increase the power supply capacity can be used. Therefore, the capacity of the power supply can be increased and the power supply efficiency can be improved, and a compact gas laser oscillator with high overall efficiency can be obtained.

[Brief description of drawings]

FIG. 1 is a configuration diagram showing a gas laser oscillator according to an embodiment of the present invention.

FIG. 2 is a schematic configuration diagram showing a power supply configuration according to an embodiment of the present invention.

FIG. 3 is an explanatory view showing the action and effect of the present invention.

FIG. 4 is a schematic diagram showing a physical configuration of discharge.

FIG. 5 is a schematic configuration diagram showing a conventional gas laser oscillator.

[Explanation of symbols]

1 ... External wind tunnel, 2 ... Internal wind tunnel, 4a, 4b ... Electrode, 10 ...
Electrode layers, 11 ... AC power supply (700 kHz or more), 13 ... Inverter circuit.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Takaaki Murata 2121 Nobu, Asahi-cho, Mie-gun, Mie Prefecture Inside the Toshiba Mie factory (72) Inventor Hirokatsu Suzuki 2121 Sayo-cho, Asahi, Mie-gun, Mie Incorporated company Toshiba Mie factory (72) Inventor Akira Moriguchi 2121 Nobu, Asahi-cho, Mie-gun, Mie prefecture Incorporated company Toshiba Mie factory

Claims (2)

[Claims] 1. A container comprising a container filled with a gas which is a laser medium, at least a pair of discharge electrodes facing each other, and an AC power supply connected to the discharge electrodes and applying an AC voltage. A gas laser oscillator characterized in that the frequency of the AC power supply is 700 kHz or higher, a solid state element is used for the AC power supply to perform switching operation, and the high frequency power output per unit is 4 kW or higher. 2. The gas laser oscillator according to claim 1, wherein an electrostatic induction type transistor is used as the solid-state element.