JPS6335116B2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to an improvement in the electrode configuration of a lateral pump laser oscillator, and in particular aims to simplify the structure of the cathode and extend its lifespan. .

[Conventional technology]

A typical example of this type of conventional laser is a so-called three-axis orthogonal CO ₂ laser in which the optical axis, discharge, and gas flow directions are substantially perpendicular to each other.

Fig. 1 is a vertical cross-sectional view of a conventional device, and Fig. 2 is a cross-sectional view of the conventional device taken along the - line, where 1 is an anode, 2 is a cathode, 3 is a cathode substrate made of an insulator, 4 is a stabilizing resistor, 5 is a DC high voltage power supply, 6 is a discharge excitation unit, 7 is a mixed gas, 8 is a total reflection mirror, and 9 is a partial reflection mirror.

Next, the operation will be explained. While flowing a mixed gas 7 consisting of CO ₂ , N ₂ , and He in the direction of the arrow in the gap between the anode 1 and a large number of cathodes 2, a DC high-voltage power supply 5 connects the anode 1 and the cathodes 2 via the stabilizing resistor 4. Applying a high voltage creates a discharge between them. In the discharge excitation part 6 generated by this discharge, an inversion and distribution is formed between specific vibrational levels of CO ₂ molecules in the mixed gas. When a total reflection mirror 8 and a partial reflection mirror 9 having an appropriate reflectance are placed facing each other with the discharge excitation part 6 in between, laser oscillation occurs and a laser beam is emitted from the partial reflection mirror 9.

In addition, in maintaining the continuous operation of the CO ₂ laser,
As is well known, it is essential to maintain the gas temperature in the discharge excitation section 6 at a low level.
As shown in Figs. 1 and 2, a large number of cathodes 2 (several hundred are used in an actual KW class laser) are arranged along the optical axis, and the cathode 2 is disposed at a rate of several tens of meters per second. The mixed gas 7 is being circulated at a high speed. The stabilizing resistor 4 connected to the cathode 2 is used to make the discharge current of each cathode the same, that is, to make the discharge belonging to each cathode homogeneous.

[Problem that the invention seeks to solve]

Next, we will briefly discuss the lifespan of the segmented cathode shown above.

The cathode 2 is usually made of metal such as Mo, W, Cu, or stainless steel. At high temperatures, these metals react rapidly with oxygen in the surrounding atmosphere, forming a layer of metal oxide on their surface and causing significant wear.

As is well known, these metal oxides (insulators) make the discharge unstable, causing a transition to arc discharge, and extremely lowering the laser output.

Under normal laser operating conditions. The heat input to the cathode due to discharge is approximately 10W per cathode (discharge current (30mA) x cathode drop voltage (300V)). It is necessary to reduce the cathode tip temperature by efficiently cooling and removing this heat input. However, in the conventional split cathode, each cathode 2
and must be electrically insulated from each other, so cooling the cathode directly with liquid would require multiple cooling liquid seals, which would be nearly impossible. In practice, each cathode 2 is cooled by the gas stream 7. In this case, under normal laser operating conditions as described above, the temperature at the tip of cathode 2 is 400°C.
It reaches ~500℃.

Conventional laser equipment uses a large number of cathodes and stabilizing resistors as described above, making the equipment extremely complex and unreliable. At the same time, the temperature of the cathode discharge surface becomes quite high, which reduces the lifetime of the cathode. It has the disadvantage that it is short. Moreover, as can be seen from FIG. 2, since the discharge excitation parts 6 are not uniformly distributed in the optical axis direction, only about half of the flow rate of the blast gas is distributed in the discharge excitation parts 6.
However, the disadvantage is that it is not useful for reducing the gas temperature, and therefore requires a large-capacity blower.

This invention was made in order to eliminate the drawbacks of the conventional ones as described above, and in addition to the anode and the cathode, a dielectric electrode covered with a dielectric material is disposed near the cathode, and the cathode and the dielectric electrode are A structure is provided in which an alternating current discharge, so-called silent discharge, is generated as an auxiliary discharge between the two, and gas is caused to flow into the direct current glow discharge space through the region of this silent discharge.
This makes it possible to unify the cathode and to form curtain-like discharge excitation parts uniformly distributed in the optical axis direction.

Before describing the present invention in detail, we will briefly discuss the advantages and disadvantages of normal DC discharge (glow discharge) and AC discharge via a dielectric (silent discharge). The advantage of glow discharge is that fairly high discharge power densities (up to about 100 W/cm ³ ) can be easily achieved. Conversely, the disadvantage is that it is difficult to achieve uniform discharge force density over a wide space. On the other hand, the advantage of silent discharge is the capacitive ballast effect.
Due to the essential homogenizing effect of the discharge, known as , it is easy to achieve a uniform discharge power density over a wide space.The disadvantage is that it is difficult to obtain a high discharge power density (at most 10 W/cm ³ ).

As is well known, high output and high efficiency
The most important things in realizing a CO ₂ laser oscillator are to achieve a high discharge power density and to ensure that the discharge is homogeneous over a wide space. The present invention combines the advantages of glow discharge and silent discharge, and makes it possible to realize a high-output laser oscillator with unprecedented high efficiency and features.

[Means for solving the problem] An anode, a cathode, a dielectric electrode disposed near the anode or cathode, and an electrode between the dielectric electrode and the anode or cathode located near the anode or cathode. an AC power supply that applies an AC voltage to generate a silent discharge between the two electrodes, generates a DC glow discharge between the anode and the cathode, and emits laser light from the optical resonator. A lateral pumping laser oscillator, characterized in that the transversely pumping laser oscillator is configured to allow gas to flow into a discharge space where a direct current glow discharge is generated through the gap where the silent discharge is generated.

〔Example〕

FIG. 3 is a longitudinal cross-sectional view of one embodiment of the present invention, and FIG. A pipe-shaped dielectric electrode 11 made of a material supplies current to the dielectric electrode 10.
A thin metal wire that serves as a so-called feeder, 1
2 is deionized water flowing to cool the dielectric electrode 10; 13 is an insulator cover for fixing the discharge path between the anode 1 and the cathode 201; 13a, 1;
3b is a slit through which the auxiliary gas 701 passes; 14 is a high-voltage AC power source for generating an alternating current (100Hz to 100KHz) discharge as a preliminary discharge between the thin metal wire 11 and the single cathode 201; the auxiliary gas 701 is an alternating current discharge The excited atoms and molecules are fed in the direction of the arrow in order to flow into the discharge space formed between the anode 1 and the single cathode 201 and where the discharge excitation part 6 is formed (hereinafter referred to as the main discharge part). be done. In this configuration, when a voltage is applied from the high-voltage AC power supply 14 between the single cathode 201 and the thin metal wire 11, an AC discharge is generated in the gap between the single cathode 201 and the dielectric electrode 10. be done. Since such AC discharge essentially has spatial homogeneity due to the presence of the dielectric electrode 10, the discharge power density within the gap becomes uniform within the gap and in the optical axis direction.

[Effect]

The ionized gas generated within the gap due to this alternating current discharge is caused to flow into the main discharge portion.

At this time, since the AC discharge is homogeneous,
The distribution of the ionized gas that has flowed into the main discharge part in the optical axis direction is homogeneous, and the flow forces the ionized gas to be evenly distributed over a fairly wide area of the main discharge part. . This has the effect of making the impedance of the discharge constant over the entire main discharge region, and prevents the concentration of discharge that is originally observed in an integrated cathode. As a result, a homogeneous main discharge can be obtained at the integrated cathode.

The discharge power of the auxiliary alternating current discharge required to bring about such remarkable homogenization of the main discharge is about 1/10 or more of that of the main discharge.

In Figures 3 and 4, the main discharge cathode does not have a particular cooling structure, but since the cathode is integrated and has an earth potential, it can be directly cooled with ordinary liquid such as water. This makes it easy to extend the life of the cathode.

In addition, in the above embodiment, the dielectric electrode 10 and the single cathode 201 were arranged coaxially, but the fifth embodiment
Even if they are arranged in parallel as shown in the figure, the same effects as in the above embodiment can be achieved. In the embodiment shown in FIG. 5, each single cathode 201 is directly cooled by cooling water 121.

Although the above explanation has shown that the auxiliary discharge means using silent discharge is provided in the cathode portion of the main discharge, the same effect can be obtained even if the auxiliary discharge means is provided in the anode portion.

It goes without saying that similar effects can be obtained even when applied to a so-called biaxial orthogonal type laser in which the gas flow direction and the discharge direction are the same and the optical axis is substantially perpendicular to them.

〔Effect of the invention〕

With the above configuration, in the present invention, the ionized gas generated in the gap due to the AC discharge is caused to flow into the main discharge part using gas, and at this time, since the AC discharge has a homogeneous distribution, the ionized gas generated in the gap is caused to flow into the main discharge part. The distribution of the ionized gas in the optical axis direction is homogeneous, and the flow forces the ionized gas to be evenly distributed over a fairly wide area of the main discharge area. This acts to keep the impedance of the discharge constant over the period of time and prevents the concentration of discharge normally observed in an integrated cathode.As a result, a homogeneous main discharge can be obtained at the integrated cathode, resulting in a highly efficient laser device. This has the effect of being able to provide the following.

[Brief explanation of the drawing]

Figure 1 is a vertical cross-sectional view of a conventional 3-axis orthogonal CO ₂ laser, Figure 2 is a cross-sectional view taken along the - line, and Figure 3 is a vertical cross-sectional view of a conventional three-axis orthogonal CO 2 laser.
The figure is a longitudinal cross-sectional view of one embodiment of the present invention, FIG. 4 is a cross-sectional view taken along the line ``--'', and FIG. 5 is a cross-sectional view of another embodiment of the present invention. In the figure, 1 is an anode, 2 is a cathode, 3 is a cathode substrate, 4 is a discharge stabilization resistor, 5 is a DC high voltage power supply, 6
is a discharge excitation part, 7 is a laser gas, 8 is a total reflection mirror,
9 is a partial reflecting mirror, 10 is a dielectric electrode, 11 is a thin metal wire, 12 is deionized cooling water, 13 is an insulator cover, 13a, 13b are slits, 14 is an AC high voltage power supply, 15 is a power supply terminal, 201 is a Single cathode, 70
1 is auxiliary gas, and 121 is cooling water. Note that the same reference numerals in the figures indicate the same or corresponding parts.

Claims (1)

[Claims] 1. An AC voltage is applied between an anode, a cathode, a dielectric electrode disposed near the anode or the cathode, and the dielectric electrode and the anode or cathode located near the dielectric electrode. A lateral excitation type, comprising an AC power source that generates a silent discharge between the two electrodes, generates a DC glow discharge between the anode and the cathode, and emits laser light from the optical resonator. A laterally pumped laser oscillator, characterized in that the laser oscillator is configured to allow gas to flow into a discharge space where a DC glow discharge is generated through the gap where the silent discharge is generated. 2.Equipped with a cylindrical cathode or anode in which a slit is formed to serve as a gas ventilation path, and a dielectric electrode housed coaxially with the cylindrical cathode or anode, the gas is introduced into the glow discharge space through the slit. A lateral pumping type laser oscillator according to claim 1, further comprising a device for supplying air. 3. The lateral excitation type according to claim 1, wherein a cylindrical cathode or anode and a dielectric electrode are arranged side by side with a gap therebetween, and gas is allowed to flow into the discharge space through the gap. laser oscillator. 4. The lateral excitation type laser oscillator according to claim 1, which is configured to cool the dielectric electrode.