JPH01192183A - Pulse gas laser device - Google Patents

Abstract

PURPOSE:To make the tail of laser rays small even if a large laser output is taken out by a method wherein an optical resonator is made variable in a resonator length synchronizing with a modulation frequency of a discharge tube. CONSTITUTION:When a pulse signal generated in a pulse generator 8 is inputted, a discharge current is impressed on a laser gas discharge tube 1 from a high voltage power source 7 and a pulse discharge is made to occur. Laser rays are resonated from an optical resonator composed of a laser output mirror 4 and a total reflection mirror 5. The total reflection mirror 5 is mounted on a piezoelectric transducer 6, so that it is shifted by half a wavelength when a DC high voltage is applied to the piezoelectric transducer 6 from a drive converter 10. A laser oscillation is made to stop due to the decrease of the optical resonator in a Q value caused by the shift of the total reflection mirror 5 or the change of the optical resonator in a resonator length. The tail of laser rays oscillated when the total reflection mirror 5 is shifted is extremely small as compared with that of laser rays oscillated when the mirror 5 is not shifted.

Description

DETAILED DESCRIPTION OF THE INVENTION Handling Blood Bean 1 The present invention relates to a pulsed gas laser device, and particularly to a carbon dioxide laser device that generates pulse oscillation by chopping a discharge current.

Nirayoto: Conventionally, in this type of carbon dioxide laser device, a pulse discharge is generated by chopping the discharge current to generate pulse oscillation of laser light.

However, in the oscillation process of a carbon dioxide laser device, the lifetime of the upper level (001°) of the carbon dioxide molecule is as long as about 11 seconds at normal gas pressure, and the gain remains even after excitation of the laser gas by pulse discharge is stopped. , the laser oscillation continues without stopping.

Therefore, as shown in FIG. 3(c), after the pulse discharge stops, the oscillation of the laser light, called a tail, continues.

In the case of a carbon dioxide laser device, nitrogen gas is mixed in addition to carbon dioxide gas, and the nitrogen molecules are first excited by electric discharge, and the energy of the nitrogen molecules is transferred to carbon dioxide molecules by collision between the excited nitrogen molecules and carbon dioxide molecules. The process takes place in which carbon dioxide molecules are excited to the upper level of the laser.

Since this nitrogen molecule is a homonuclear binary molecule, once it is excited, it will not lose energy unless it collides with another component. Therefore, the higher the mixing ratio of nitrogen gas, the more
Although the tail of the laser beam becomes longer, in the case of a carbon dioxide laser device, the electric input for discharge cannot be applied unless the nitrogen gas partial pressure is increased to a certain degree.

For this reason, when attempting to extract a large amount of laser output and reduce the tail of the laser beam, there is a drawback that controlling the nitrogen gas partial pressure alone is difficult.

The present invention was made in order to eliminate the above-mentioned drawbacks of the conventional ones, and its purpose is to provide a pulsed gas laser device that can reduce the tail of laser light even when extracting a large amount of laser output. do.

The pulsed gas laser device according to the present invention is a pulsed gas laser device that performs continuous pulse oscillation by applying a modulated discharge current to a laser gas discharge tube within an optical resonator, and the pulsed gas laser device performs continuous pulse oscillation by applying a modulated discharge current to a laser gas discharge tube in an optical resonator. The present invention is characterized in that a variable means for varying the resonator length of the optical resonator in synchronization with the modulation frequency is provided.

K1 Next, one embodiment of the present invention will be described with reference to the drawings.

FIG. 1 is a configuration diagram showing the configuration of an embodiment of the present invention.
In the figure, a carbon dioxide laser device according to an embodiment of the present invention includes a laser gas discharge tube 1, a cathode electrode 1ff12, 7/Ft4i3, a laser output mirror 4, a total reflection mirror 5, and a piezoelectric transducer (PZT) 6. , a high voltage power supply 7, a pulse generator 8, a timing circuit 9, and a piezoelectric converter driving converter (hereinafter referred to as the driving converter) 10.
It is composed of:

FIG. 2 is a timing chart of one embodiment of the present invention. FIG. 2(a) shows the pulse signal from the pulse generator 8, and FIG. 2(b) shows the waveform of the discharge current flowing through the laser gas discharge tube 1.

Moreover, FIG. 2(c) shows the waveform of the laser beam when the total reflection mirror 5 is not shifted.

Further, FIG. 2(d) shows the DC high voltage supplied from the drive converter 10 to the piezoelectric converter 6, and FIG. 2(e)
shows the waveform of laser light when the total reflection mirror 5 is shifted by the piezoelectric transducer 6.

FIG. 3 is a diagram showing the relationship between the gain curve of a carbon dioxide laser and the longitudinal mode. The operation of one embodiment of the present invention will be explained using these FIGS. 1 to 3.

When the pulse signal generated by the pulse generator 8 is input to the discharge control section (not shown) of the high voltage power supply 7 via the timing circuit 9, a discharge current is applied from the high voltage power supply 7 to the laser gas discharge tube 1. , a pulse discharge is generated in the laser gas discharge tube 1 by the cathode electrode 2 and the anode electrode 3 [see FIGS. 2(a) and 2(b)].

At this time, due to the stray capacitance of the laser gas discharge tube 1 and the discharge circuit system such as the high voltage power supply 7, the discharge current flowing through the laser gas discharge tube 1 has a waveform as shown in FIG. 2(b).

This pulse discharge causes the laser output mirror 4 and the total reflection 115
Laser light is oscillated from an optical resonator configured with.

At the same time, a pulse signal from pulse generator 8 is input to drive converter 10 via timing circuit 9, and drive converter 10 applies a DC high voltage to piezoelectric converter 6 in response to this signal.

Since the total reflection mirror 5 is mounted on the piezoelectric transducer 6,
Application of a DC high voltage from the drive converter 10 to the piezoelectric transducer 6 causes a shift by a half wavelength.

Due to this shift of the total reflection mirror 5, that is, a change in the resonator length of the optical resonator, the Q value of the optical resonator decreases and laser oscillation is stopped. [See Figures 2(d) and (e)].

Therefore, the laser light when the total reflection mirror 5 is shifted by the piezoelectric transducer 6 [see FIG. 2(e)] is different from the laser light when the total reflection mirror 5 is not shifted [see FIG. 2(c)]. There is an extremely small tail compared to .

Here, when the resonator length of the optical resonator is changed to Q by shifting the total reflection mirror 5, the gain curve shown in FIG. 3 is shifted by Δv with respect to the oscillation frequency v0 before the change.

The oscillation frequency ν at this time. If 6g is selected so that the gain at ±Δ is smaller than the oscillation threshold, laser oscillation will be stopped. However, in the case of a carbon dioxide laser, the laser oscillation does not occur at just one oscillation frequency, but includes several oscillation frequencies, so the laser oscillation at all oscillation frequencies does not stop. Due to the laser oscillation of the oscillation frequency, a slight tail remains in the laser beam.

In the case of a carbon dioxide laser, as shown in Fig. 3, the Doppler width, which is the gain width, is approximately 50 MHz, and the longitudinal mode interval C/2L is 150 MHz even if L = 1 m, so this gain width There is always only one vertical mode in the image. That is, Δν is at least C/
It can be made smaller than 2L, so 6g is at most 2L (λ
/2) The following is sufficient.

FIG. 4 is a block diagram showing the configuration of another embodiment of the present invention. In FIG. The structure is similar to that of the embodiment, and the same components are given the same reference numerals. Further, the operations of these components are also similar to those of the components of the carbon dioxide laser device according to one embodiment of the present invention.

Here, in FIG. 2, the high voltage power supply 7, pulse generator 8, timing circuit 9, and drive converter 10 shown in FIG. 1 are omitted.

Carbon dioxide lasers have many oscillation frequencies due to transitions between many vibrational and rotational levels of carbon dioxide molecules.
A resonator is constituted by a gold reflecting mirror on which gold is vapor-deposited, and when laser oscillation is performed from this resonator, the laser oscillates in the 10.6 μs band P(20) where the gain is highest due to a competitive effect.

However, by inserting the diffraction grating 11, which is a wavelength selection element, into the resonator, it is possible to select one of many oscillation frequencies for oscillation. Even in such a case, a laser beam with a small tail can be obtained by shifting the total reflection 1i5.

Figure 5 shows the difference in processing characteristics when the tail of the laser beam is large and small.
00-) shows the processing characteristics when laser scribing a ceramic (alumina, etc.) substrate.
FIG. 5(a) shows the processing characteristics when the tail of the laser beam is large, and FIG. 5(b) shows the processing characteristics when the tail of the laser beam is small.

If the tail of the laser beam is large, not only will the laser scribe process not penetrate deeply, but the portion corresponding to the tail of the laser beam will be greatly raised on the time axis. This is a ceramic that is once melted by the heat of the laser beam and then recrystallized into a glassy state.

However, when the tail of the laser beam is small, the depth in the laser scribing process becomes deep, and the bulge corresponding to the tail of the laser beam on the time axis is not very large.

As mentioned above, processing characteristics that cause large bulges on the surface of a ceramic substrate are not desirable, and it is desirable to minimize bulges on the surface of a ceramic substrate, and for this purpose, it is important to minimize the tail of the laser beam.

In this way, the laser output mirror 4 and the total reflection mirror 5 are synchronized with the modulation frequency of the discharge current applied to the laser gas discharge tube 1.
By varying the resonator length of the optical resonator consisting of the total reflection mirror 5 and the piezoelectric converter 6, the tail of the laser beam can be made small even when a large amount of laser output is extracted.

Note that in one embodiment and other embodiments of the present invention, the total reflection mirror 5
Although the resonator length of the optical resonator was changed by shifting the laser output mirror 4, it is also possible to change the resonator length of the optical resonator by shifting the laser output mirror 4. Furthermore, in one embodiment and other embodiments of the present invention, a carbon dioxide laser device has been described;
It is obvious that the present invention can be applied to other pulsed gas laser devices, and is not limited thereto.

As explained above, according to the present invention, the resonator length of the optical resonator is varied in synchronization with the modulation frequency of the discharge current applied to the laser gas discharge tube, thereby increasing the laser output. Even when a large amount of laser light is extracted, the tail of the laser beam can be made small.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing the configuration of an embodiment of the present invention, FIG. 2 is a timing chart of an embodiment of the present invention, and FIG. 3 is a diagram showing the relationship between the gain curve and longitudinal mode of a carbon dioxide laser.
FIG. 4 is a configuration diagram showing the configuration of another embodiment of the present invention, and FIG.
The figure shows the difference in processing characteristics when the tail of the laser beam is large and when the tail is small. Explanation of symbols of main parts 1... Reig gas discharge tube 4... Laser output mirror 5... Total reflection mirror 6... Piezoelectric transducer (PZT) 7 ...High voltage power supply 8 ...Pulse generator

Claims (1)

[Claims] (1) A pulsed gas laser device that performs continuous pulse oscillation by applying a modulated discharge current to a laser gas discharge tube within an optical resonator, the optical resonator oscillating in synchronization with the modulation frequency of the discharge current. A pulsed gas laser device characterized by being provided with variable means for varying the resonator length.