JP2789278B2 - High frequency discharge pumped laser oscillator - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a high-frequency discharge pumped laser oscillator having an auxiliary discharge device.

[0002]

2. Description of the Related Art A high-frequency discharge excitation laser oscillator having an auxiliary discharge device has been developed. FIG. 2 shows an oscillator 1 of this kind.
The main electrode 3 is provided on the outer periphery of the discharge tube 2 mechanically.
a, 3b and the auxiliary electrode 4 are arranged. Main electrode 3
(A, b) are arranged to face each other, and the auxiliary electrode 4 is
Are arranged adjacent to and adjacent to the main electrode 3a on the power supply S side in the tube axis direction of the power supply S. The auxiliary electrode 4 is made of Teflon (trade name)
The main electrode 3 (a, b) is connected to the earth E side of the main body 3 (a, b). That is, one of the main electrodes 3 (a, b), the auxiliary electrode 4, and the connection between them constitute an auxiliary discharge device. Reference numeral 6 denotes a cooling fin, and a CO ₂ gas exists as an excitation medium inside the discharge tube 1, and a laser beam is output in the tube axis direction indicated by an arrow.

When a high voltage is applied between the main electrodes 3 (a, b) to start a main discharge, the auxiliary discharge device in the oscillator 1 is connected to the main electrode 3 a on the power source S side and the dielectric 5. The potential difference between the auxiliary electrodes 4 mounted close to the main electrode 3a becomes large, and a discharge (auxiliary discharge) occurs between these electrodes.
Lights up. Subsequently, even if the main discharge is turned on between the main electrodes, the above-mentioned auxiliary discharge is maintained due to the hysteresis of the discharge condition.

Thus, for example, in laser processing, it is necessary to temporarily stop the main discharge when moving the spot from the end point of one processing line to the start point of the next processing line, but the main discharge is stopped. During such a period, the auxiliary discharge 7 is maintained, and the rise when the main discharge is restarted is performed easily and in a short time. When the laser output is maintained at a low level, the discharge state fluctuates and the laser output becomes unstable with only the main discharge.
The presence of the auxiliary discharge 7 facilitates stable output control.

As described above, the auxiliary discharge device is effective in improving the performance of the high-frequency discharge excitation laser oscillator 1 and obtaining better laser light for high-speed fine processing. Since the potential difference from the main electrode 3a is obtained electrostatically, it is arranged closer to the main electrode 3a than the distance between the main electrodes 3 (a, b), and the dielectric constant is reduced. Therefore, it is attached to the discharge tube 2 via the dielectric 5.

For this reason, when the voltage between the main electrodes 3 (a, b) increases, a corona discharge occurs between the main electrode 3 a and the auxiliary electrode 4 on the outer periphery of the discharge tube 2, which may damage the electrodes. This hinders the auxiliary discharge device from increasing the output of the oscillator 1. In addition, since the function of the dielectric 5 depends on material characteristics, there is a problem in characteristics variation and durability, and the reliability is low.

[0007]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a high-frequency discharge-excited laser oscillator having an auxiliary discharge device which is highly reliable without damaging electrodes for discharge excitation.

[0008]

SUMMARY OF THE INVENTION The present invention relates to a high frequency discharge pumped laser oscillator. The discharge tube has a main electrode and an auxiliary electrode. A resonance coil is connected between the auxiliary electrode and the ground or between the auxiliary electrode and the power source, and the equivalent capacitance between the main electrode and the auxiliary electrode causes the resonance frequency to be the frequency of the high-frequency power source applied between the main electrodes. Configure the circuit.

[0009]

The resonance circuit increases the voltage between the main electrode and the auxiliary electrode, turns on and maintains the auxiliary discharge.

[0010]

FIG. 1 shows an example of a high-frequency discharge pumped laser oscillator according to the present invention. The oscillator 1 includes a discharge tube 2 and a main electrode 3 (a, b) facing the same as in the above-described conventional example. The auxiliary electrode 4 is directly fixed to the outer peripheral surface of the discharge tube 2 on the side of the main electrode 3a on the power supply S side. The distance between the main electrode 3a and the auxiliary electrode 4 in the tube axis direction is substantially equal to the interval between the main electrodes 3 (a, b). The auxiliary electrode 4 is connected to the ground E via a resonance coil 8. The connection connecting the main electrode 3a and the auxiliary electrode 4 and the resonance coil 8 therebetween constitutes an auxiliary discharge device.

The inductive reactance of the resonance coil 8 and the capacitance reactance of the equivalent capacitance between the main electrode 3a and the auxiliary electrode 4 have a resonance frequency substantially equal to the frequency of the high-frequency power supply applied between the main electrodes 3 (a, b). To be. That is, a resonance circuit including the power source S-side main electrode 3a, the auxiliary electrode 4, and the resonance coil 8 is formed. Note that CO ₂ gas exists as an excitation medium inside the discharge tube 2. .

In this configuration, when a high-frequency discharge voltage is applied between the main electrodes 3 (a, b), before the main discharge is started, the main electrode 3 a and the auxiliary electrode 3 a are resonated by resonance in the resonance circuit. The voltage between the electrodes 4 becomes high, and the auxiliary discharge 7 is turned on between the two electrodes inside the discharge tube 8. Once the auxiliary discharge is turned on, the impedance between the main electrode 3a and the auxiliary electrode 4 greatly changes, the resonance with the resonance coil shifts, and the voltage between the two electrodes decreases. However, the lit auxiliary discharge is maintained as it is by the hysteresis relating to the discharge condition. On the other hand, this voltage drop causes the auxiliary electrode 4
A large current is prevented from flowing to the side.

Next, the main discharge is turned on to excite the CO ₂ gas inside the discharge tube 2 and output a laser beam.
And, as in the past, the auxiliary discharge is continued even if the main discharge is temporarily stopped to move the spot from the end point of one processing line to the start point of the next processing line,
As a result, when the main discharge is turned on again, it is possible to quickly start up to the laser oscillation state. This means that machining from the start point of a new machining line can be quickly resumed. In addition, when a low laser output is required, the voltage between the main electrodes 3 (a, b) is low, and the state of the main discharge is unstable, the auxiliary discharge 7 maintains the excited state of the excitation medium. Work in the direction to keep the laser output stable.

As described above, the auxiliary discharge 7 is maintained during the operation of the oscillator 1. For some reason, even if the auxiliary discharge is cut off, the cutoff restarts the resonance of the resonance circuit and the main electrode 3a. And the voltage between the auxiliary electrode 4 is increased, and the auxiliary discharge 7 is immediately recovered. The above is one embodiment, and the present invention is not limited to this embodiment.
For example, a structure in which the auxiliary electrode 4 is attached to the side of the earth E-side main electrode 3b in the discharge tube 2 and connected to the power source S via the resonance coil 8 may be used. Further, in the above embodiment, the distance between the main electrode 3a and the auxiliary electrode 4 is different from that of the main electrode 3 (a,
b) The interval may be larger or smaller than the interval between them.

[0015]

The auxiliary discharge is lit by the increase in the voltage between the main electrode and the auxiliary electrode due to the resonance of the resonance circuit, and after lighting, the voltage between the two electrodes decreases. No corona discharge occurs between the electrode and the auxiliary electrode. Thus, a higher voltage than before can be applied between the main electrodes without being affected by the presence of the auxiliary electrodes, and a higher laser output can be achieved. Since the auxiliary discharge is lit by resonance of the resonance circuit, the continuation and maintenance of the auxiliary discharge is extremely high. The characteristics of the resonant coil as a circuit element are always more stable than dielectric materials that depend on material characteristics, and there is little variation among individual elements, so the stability of auxiliary discharge is high, The reliability of the auxiliary discharge device is dramatically improved together with the above-mentioned continuous maintenance capability.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view mechanically showing a cross-section (embodiment of the present invention).

FIG. 2 is a sectional view (conventional example) mechanically shown in section.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 High frequency discharge excitation laser oscillator 2 Discharge tube 3 Main electrode 4 Auxiliary electrode 5 Dielectric 6 Cooling fin 7 Auxiliary discharge 8 Resonant coil

──────────────────────────────────────────────────続 き Continued on front page (58) Field surveyed (Int.Cl. ⁶ , DB name) H01S 3/0977

Claims (1)

(57) [Claims] 1. A high frequency discharge pumped laser oscillator comprising:
It has a main electrode and an auxiliary electrode, and a resonance coil is connected between the auxiliary electrode and the ground or between the auxiliary electrode and the power supply, and the frequency of the high frequency power supply applied between the main electrodes by the equivalent capacitance between the main electrode and the auxiliary electrode. A high frequency discharge pumped laser oscillator comprising: a resonance circuit having a resonance frequency of: and an auxiliary discharge device for generating and maintaining an auxiliary discharge between the main electrode and the auxiliary electrode by resonance.