JPH0380582A - Pulse discharge excitation laser device - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a pulse discharge excitation laser device that uses microwave discharge as a pre-ionization source.

[Conventional technology]

As a pulse discharge excitation laser device, TEA (tra
nsverslyexcited, atmospher
ic) There are Cot laser devices, excimer laser devices, etc., but since the device configurations are similar, the excimer laser device will be explained as an example.

Figure 3 is from CMC Co., Ltd. in 1986.
The book ``Excimer Laser Cutting-Edge Applied Technology, Vol.
This is a conceptual diagram of the discharge excitation part of a conventional ultraviolet preionization excimer laser device using arc discharge, and Figure 4 is a conceptual diagram of the discharge excitation section of a conventional excimer laser device using ultraviolet rays pre-ionization method, which was published on the page 42-44 of the same book. This is a conceptual diagram of the discharge excitation part of an ultraviolet preionization excimer laser device using corona discharge, and Figure 5 shows the discharge excitation part of an X-ray preionization excimer laser device published on pages 19 to 20 of the same book. FIG. 3 is a conceptual diagram of an excitation section. In each case, the direction perpendicular to the plane of the paper is the laser optical axis direction, and a cross section perpendicular to the coaxial direction is shown.

In Fig. 3, (1) and (2) are a pair of main electrodes facing each other, (3) is a main discharge formed between these main electrodes (main discharge space), and (4) is Doryu fi (1 ) and (2), a power source for causing the main discharge (3), (5)
and (5^) are pre-ionization bottle electrode pairs provided along the longitudinal direction (laser optical axis direction) of main ionization (1) and (2) in order to cause arc discharge as a pre-ionization source. , (6) is the arc discharge formed between this pair of bottle electrodes, and (7) is the ultraviolet light generated from this arc discharge.

In FIG. 4, (8) is the main electrode with an opening, (9
) is a dielectric provided on the side of this main electrode (8) opposite to the main electrode (1), and (10) is provided on the side of this dielectric (9) opposite to the main electrode (1). and an auxiliary electrode connected to the electrode (4). (11) is a corona discharge formed between the main electrode (8) and the dielectric (9).

In FIG. 5, (12) is a main electrode that is thinly arranged so that X-rays (described later) can pass therethrough, and is connected to a power source (4). (13) is an X-ray source, and (14) is an X-ray generated by this X-ray source (13).

Next, the operation will be explained. In the excimer laser device shown in Fig. 3, before a high voltage is applied to the main electrodes (1) and (2), a voltage is applied between the pair of bin electrodes (5〉 and . (6) occurs. The ultraviolet light (7) generated from this arc discharge (6) photodissociates the gas in the main discharge space and creates seed electrons in the main discharge space. Then, from the power source (4) to the main electrode ( When the high voltage applied to 1> and 2) reaches the breakdown voltage, a main discharge (3) is formed in the entire area between the main electrodes (1) and (2), triggered by the seed electrons. If seed electrons are not dispersed in the main discharge space (pre-ionization) in advance, the main discharge (3) will not be formed in the entire area between the main electrodes (1) and (2), but will be formed at one point. Only Kamiteri-like arc discharge occurs, and laser gas excitation is not performed effectively.

The excimer laser device shown in FIG. 4 performs the pre-ionization operation described in "2" using corona discharge.

There, first, the open-hole main mold i (8) and the auxiliary chamber ffi (
A voltage is applied between 10), a corona discharge (11) is formed through the dielectric (9), and ultraviolet rays from this corona discharge (11) reach the main discharge space through the opening, and the main discharge space becomes a reserve. ionized. There is also the effect that electrons from the corona discharge (11) are directly drawn out into the main discharge space through the openings. The advantage of this excimer laser device over the excimer laser device shown in FIG. 3 is that since corona lightning, which is softer than arc discharge, is used as a preliminary ionization source, there is less deterioration of the laser gas.

However, the method using these discharges as a preliminary ionization source has the following drawbacks. In the excimer laser device shown in Fig. 3, since the arc discharge as a pre-ionization source is localized, even if the number of bin electrode pairs (5) (5^) is increased, the number of seed electrons generated in the main discharge space will be reduced. Unevenness occurs in density.On the other hand,
Even in the excimer laser device shown in Fig. 4, it is difficult to cause corona discharge evenly in the parts corresponding to all the openings, and there are openings where corona discharge is strongly occurring and holes where corona discharge is not occurring. As a result, the density of millet grains is spatially uneven.

As a method for obtaining a spatially even and uniform distribution of seed electrons, there is an X-ray preionization type excimer laser device shown in FIG. This excimer laser device uses a method of injecting uniform X-rays (14) emitted from an X-ray source (13) into the main discharge space through a thin metal main electrode (12), which originally performs pre-ionization with uniform X-rays. Therefore, it is possible to realize the formation of spatially uniform seed electrons.However, in this method, an X-ray source (13) must be added to the device in addition to the laser oscillator, which complicates the structure.Also, The X-ray source itself also
Problems to be solved by the invention include the need for extremely high voltage to generate a line, difficulty in repeating operations as quickly as several hundred times per second like pre-ionization using discharge, and short lifespan. ] Conventional pulsed discharge excitation laser equipment is configured as described above, so if arc discharge or corona discharge, which has a long life and is compatible with rapid repetitive operation, is used as a preliminary ff1M source, unevenness will occur in the seed electron density distribution. However, there were problems in that the main discharge itself was non-uniform, the stability of the discharge was low, and the laser efficiency was low.

On the other hand, the X-ray pre-ionization method that provides a uniform seed electron density distribution has the problem that the life of the X-ray source is short and rapid repetitive operation cannot be performed.

This invention was made in order to solve the above-mentioned problems, and it provides a pulse discharge that has a pre-ionization source that provides a uniform seed electron density distribution in the main discharge space and that is capable of long-life and rapid repetitive operation. The purpose is to obtain an excitation laser device.

[Means to solve the problem]

The pulse discharge excitation laser device according to the present invention is provided with a microwave circuit that generates microwave discharge and a microwave generation source as a preliminary ionization source for distributing and supplying seed electrons to the main discharge space. .

[For production]

In this invention, by using microwave discharge as a pre-ionization source, a uniform seed electron density distribution is given to the main discharge space, thereby obtaining a uniform main discharge.

〔Example〕

An embodiment of the present invention will be described below with reference to the accompanying drawings.

FIG. 1 is a sectional view showing one embodiment of the present invention. In FIG. 1, (1> to (4) are exactly the same as those explained in FIG. 3. (15) is a microwave generation source. ,
(16) is a waveguide connected to this microwave generation source (15), (17) is a microwave coupling window provided at the end of this waveguide (17), and (18) is this microwave The cavity wall (19) following the joining window <17> is connected to this cavity wall (18).
The ridge (20), which is a convex part provided in the center of It has an opening.

(21) is a conductor! (22) is the space formed between the conductor wall (20) and the dielectric (21), (23> is the space formed between the conductor wall (20) and the dielectric This is the microwave discharge formed during (21).

The pulse discharge excitation laser device of the present invention is constructed as described above, and its operation will be explained in detail below. The microwave generated by the microwave source (15) propagates through the waveguide (16) and is connected to the ridge (19) by impedance matching at the microwave coupling window (I7).
> to the cavity wall (18). The microwaves are concentrated near the ridge (19) and generate a very strong microwave electromagnetic field. Due to this strong electromagnetic field, the laser gas in space (22) is destroyed by discharge, and microwave discharge (23) occurs.
is formed. Light and electrons generated from this microwave discharge (23) are introduced into the main discharge part through the conductor wall <20> having an opening, and pre-ionize the main discharge part 6
On the other hand, a pulsed high voltage is applied to the main electrodes (1) and (2) from a power source (4), and a main discharge (3) is formed using the M electrons generated by the preliminary ionization as a trigger. Here, the microwave discharge (23) will be explained in more detail.7 Like the ridge cavity in this embodiment, the microwave circuit forms an electric field component mode perpendicular to the boundary between the dielectric (21) and the discharge plasma. In this case, the dielectric (21) and the conductive wall (20) having an opening are installed facing each other, so the conductive wall (20) also has a perpendicular electric field component, causing a discharge. An electric field is created that penetrates the plasma. At this time,
Even if a conductive plasma is generated, there is a conductive wall (20) that is several orders of magnitude more conductive than the plasma, facing the dielectric (21) that is the microwave incidence window, so the terminal current of the microwave is flows through this conductor wall (20) and flows through the conductor wall (20).
The electric field near 0) is forced perpendicular to the surface of the conductor wall (20) to maintain an electric field penetrating the plasma. Therefore, the microwave penetrates into the plasma, a current flows through the plasma, and due to the continuity of the current, a discharge plasma that is spatially uniform in the depth direction of the plasma is generated. Furthermore, the microwaves that propagate freely in the dielectric (21) uniformly enter the plasma from the boundary between the dielectric (21) and the plasma, and the microwave discharge is an electrodeless discharge and essentially an arc discharge. Because the dielectric material (21) has a capacitive ballast effect, a discharge plasma that is spatially uniform in the lateral direction of the plasma is obtained, and as a result, a spatially uniform volume is obtained. A discharge is achieved. Therefore,
An extremely uniform N electron density distribution is formed in the main discharge space that is preionized by the spatially uniform preionization source, making it possible to generate an extremely uniform and stable main discharge. In addition, the microwave source (15) may be a high voltage of about 50 to 100 KV such as an X-ray source or a high voltage of 10'-'mm.
1lI? No need for high vacuum and repeatable ktl
z or more, and has an order of magnitude longer life than an X-ray source.

FIG. 2 is a sectional view showing another embodiment of the invention,
In the figures, the same reference numerals as those shown in FIG. 1 indicate the same or corresponding parts.

In another embodiment shown in FIG. 2, one of the opposing main electrodes is used as an aperture electrode, which also serves as the conductive wall (20) having an aperture in the embodiment shown in FIG. This is how it was done. The operating principle is the same as that of the embodiment described above, but it has the following features. In other words, in one embodiment, since the preionization effect is exerted from the side surface of the main electrode, if a wide main electrode is made for the purpose of forming a wide main discharge, the penetration ability of light and electrons from the preionization source will be reduced. Due to the limit of In the case of the main electrode of , a main discharge without hollow areas is also formed. Of course, when the main electrode gear has a long gap,
In the direction of the gap, there are places where preliminary ionization is not performed due to the limit of penetration ability, but this is sufficiently alleviated by avalanche in the main discharge formation process.

It is desirable that the opening diameter be large enough to allow pre-ionization light and electrons to pass through, but on the other hand, it must be below a certain size in order to confine the microwaves in the microwave discharge space6. As a result of the experiment, the aperture diameter is
It has been found that it is best to set the wavelength to 1/10 to 1/100 of the microwave wavelength.

Further, in one embodiment, an example in which preliminary ionization is performed only on one side surface has been described, but preliminary ionization may be performed on both side surfaces. In other embodiments, it has been described that one of the main electrodes is an aperture electrode, but both main electrodes may be an aperture electrode, and preliminary ionization may be applied from behind both main electrodes.

Furthermore, although a ridge cavity type has been described as an example of a microwave discharge structure, it is not possible to create a structure in which a microwave discharge is formed and light and electrons from this microwave discharge can be taken out through apertures for pre-ionization. Therefore, no restrictions are placed on the type of microwave discharge or the type of microwave generation source.

〔Effect of the invention〕

As described in detail above, the present invention is equipped with a microwave circuit and a microwave generation source that generate microwave discharge as a preliminary ionization source to supply seed electrons to the main discharge space in advance, so that uniform The preliminary ionization discharge also makes the seed electron density distribution in the main discharge space uniform, which makes the main discharge itself uniform and stable, and has the effect of making laser oscillation more efficient, more slow to heat, and longer in life.

[Brief explanation of drawings]

FIG. 1 is a sectional view showing an embodiment of the present invention, and FIG. 2 is a sectional view showing an embodiment of the present invention.
Cross-sectional views showing other embodiments of the invention, FIGS. 3 to 5
The figure is a cross-sectional view showing a conventional pulse discharge excitation laser device. In the figure, (1) and (2> are a pair of main electrodes facing each other, (3) is a main discharge, (4) is a power source, (15) is a microwave generation source, (16> is a waveguide, (17) is the microwave coupling window, (18) is the cavity wall, (19) is the ridge, (20)
(21) is a dielectric material, (22) is a conductive wall (20
) and the dielectric (21), the space <23) is a microwave discharge. In each figure, the same reference numerals indicate the same or corresponding parts.

Claims (1)

[Claims] (1) In a laser device in which a pulsed voltage is applied to a main discharge space to form a pulsed main discharge and a laser medium is excited by this main discharge to obtain laser oscillation, seed electrons are supplied in advance to the main discharge space. 1. A pulse discharge excitation laser device comprising a microwave circuit for generating microwave discharge and a microwave generation source as a pre-ionization source for the purpose of the present invention.