JPH053153B2 - - Google Patents

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention is directed to a pulsed laser capable of highly efficient and high output oscillation in the ultraviolet region, and more specifically, to a pulsed laser capable of generating high frequency noise incidentally during laser oscillation. The present invention relates to a pulsed laser tube having a structure that can be suppressed.

(Prior Art) Excimer lasers are known as pulsed lasers that can oscillate with high efficiency and high power in the ultraviolet region.

This excimer laser uses a mixture of a small amount of halogen gas, rare gas, and buffer gas as the laser material.

For example, in the case of an excimer laser using XeCl that produces output at a wavelength of 308 nm, the pressure ratio is about 0.1%.
HCl and about 1% Xe are mixed with He buffer gas to create a mixed gas with a total pressure of 3 atmospheres.

To obtain excimer laser light, there are two ways to excite this gas: ○When particularly high-output light is required, the electron beam excitation method uses a high-energy electron beam as the input energy source, and ○The high repetition rate method, which is usually used exclusively. There is one that can be excited by discharge excitation.

The latter type of discharge-excited excimer laser rapidly injects a high-energy charge into a capacitor through a switch into the gas between the anode and cathode in the laser tube, generating the energy needed to generate excimer molecules. Satisfy the conditions and discharge.

Since this discharge is a pulse discharge that rises quickly, an electromagnetic wave with a high frequency (about 100 MHz) component is generated, and since the discharge energy is also large, the generated electromagnetic wave is inevitably of high energy.
The mechanism of radiation of electromagnetic waves having high frequency components will be explained together with the operation of a conventional excimer laser device using discharge excitation.

FIG. 5 is a schematic diagram for explaining the operation of a conventional excimer laser device using discharge excitation.

Inside the excimer laser tube, the pressure ratio is about 0.1%.
A mixed gas containing HCl and about 1% Xe mixed with He buffer gas is sealed at a total pressure of about 3 atmospheres.

Rod-shaped anode (A) 12, cathode (K) 1
3 are arranged along the tube axis in the direction perpendicular to the plane of the paper.

The capacitor (C ₁ ) 3 is charged by a current supplied from the DC power source (Vo) 1 via the resistor (R) 2 and the charging coil (L) 8.

The resistance side pole of the capacitor (C ₁ ) 3 is charged positively, and the pole on the charging coil (L) 8 side is charged negatively. When a pulse of approximately -1KV is applied to the cathode 7 of the thyratron switch 4, the thyratron switch 4
is energized, but is normally kept in a non-conducting state.

To cathode 7 of thyratron switch 4 -
When a 1KV pulse is applied, the capacitor (C ₁ )
The positive charge 3 passes through the grid 6 of the thyratron switch 4 and through the spark gap 11 in the laser tube 9 to charge one electrode of a capacitor 10 disposed in the laser tube 9.

The laser tube 9 is made of an insulating material such as glass, or at least an insulating material except for the portion that is energized from an external circuit.

On the other hand, the negative charge of the capacitor 3 follows the path '' and charges the other electrode of the capacitor (C ₂ ) 10. When the voltage between the two poles due to charging of the capacitor (C ₂ ) 10 reaches a certain value [discharge starting voltage determined by the discharge gap between the spark gap 11, the anode (A) 12, and the cathode (K) 13],
is discharged between the anode (A) 12 and cathode (K) 13 through the path. spark gap 1
1 and the capacitor (C ₂ ) 10 are an anode (A) 12 and a cathode (K) 13 that extend in a rod shape in the tube axis direction.
A plurality of them are arranged along 11, and when a positive charge passes through 11, the gas body is discharged, causing a pre-ionization discharge. During this pre-ionization discharge, ultraviolet light is generated,
This is anode (A) 12 and cathode (K) 13
ionizes the gas in between.

Before the main discharge is started between the anode and the cathode by path is obtained.

A large noise occurs when the charge passes through the spark gap 11 and pre-ionizes.

A plurality of spark gaps 11 are arranged along the tube axis, and the discharge here essentially becomes an arc discharge, so the current becomes large and a large amount of noise is generated.

(Problems to be Solved by the Invention) As mentioned above, in the conventional excimer laser device, when the excimer laser oscillates, high-energy laser light is obtained and at the same time, high-energy electromagnetic waves are generated. It becomes noise.

This noise cannot be ignored and has become a problem, as it can disturb the electronic circuitry of the excimer laser device's control system, or in severe cases, even destroy the memory contents of the computer surrounding the laser.

An object of the present invention is to provide a pulsed laser tube as described above, which can minimize unnecessary electromagnetic noise generated during discharge excitation.

(Means for Solving the Problems) In order to achieve the above object, the pulsed laser tube according to the present invention transfers the electric charge charged in the capacitor through a spark gap in the laser tube via a switch element to another for discharge excitation. A pulsed laser that performs laser oscillation by charging a capacitor and discharging the charge between an anode and a cathode through the spark gap, the pulse laser having first and second discharge assemblies consisting of an anode, a cathode, a spark gap, and another capacitor. and at least the discharge direction of the anode, cathode of the first assembly and the anode, cathode of the second assembly are opposite, or the discharge direction of the spark gap of the first assembly and the discharge direction of the spark gap of the second assembly are opposite. The discharge directions of the spark gaps of the assemblies are reversed and each assembly is configured to operate simultaneously.

A thyratron is suitable as the switch element.

The other capacitors in each set may be placed either inside or outside the tube.

If the discharge directions of the anode and cathode of each of the above assemblies are opposite, and the direction of the spark gap is also opposite, the generation of electromagnetic waves due to the discharge of the anode and cathode will cancel each other out, and the generation of electromagnetic waves due to the discharge between the spark gaps will cancel each other out. Ru.

(Example) Hereinafter, the present invention will be described in more detail with reference to the drawings and the like.

FIG. 1 is a sectional view showing the principle of an embodiment of a pulsed laser tube according to the present invention.

Power supply (Vo) 21, Thyratron switch 24,
The basic functions of the charging resistor 22, coil 28, etc. of the capacitor (C ₁ ) 23 are as described in the conventional example.

Inside the laser tube 29, there are an anode (A) 32 and a cathode (K) 3 that form a first main discharge gap.
3. A first discharge assembly () consisting of a capacitor (C ₂ ) 30 and a spark gap 31, an anode (A) 37 forming a second main discharge gap, a cathode (K) 38, and a capacitor (C ₂ ) 35; A second discharge assembly () consisting of a spark gap 36 is provided.

When the thyratron switch 24 is turned on, the positive charge charged in the capacitor (C ₁ ) 23 is transferred to the capacitors (C ₂ ) 30 and 35 along the path indicated by
Charge one pole of the The negative charges pass through the spark gaps 31, 36 along the path indicated by ', and pre-ionize the gas while discharging the capacitor (C ₂ ) 30,
Charge the other pole of 35.

When the charging of the capacitors (C ₂ ) 30 and 35 progresses and the voltage between the two poles of each capacitor reaches a certain value (discharge starting voltage determined by the spark gap and the discharge gap between the anode and cathode),
This time, the charges stored in the capacitors (C ₂ ) 30 and 35 move along the path ', and eventually a main discharge is obtained between the anode and cathode of the first and second discharge assemblies, and at this time the laser beam is emitted. Occur.

Here, the electric charge flows ', ' passing through the spark gaps 31 and 36 are in opposite directions, so that even if an arc is discharged with a large current, the electromagnetic waves generated are canceled by both, and no noise is generated.

Similarly, in the main discharges of the first and second discharge assemblies, the directions '' are opposite to each other in each assembly, so the electromagnetic waves generated by the main discharges are also canceled out.

As a result, according to the present invention, the noise of the excimer laser, which has conventionally been accompanied by large noise generation, can be reduced.

In reality, there is noise generated from circuits outside the laser tube 29, so it cannot be completely eliminated, but the present invention can suppress the generation of large noise, which has been a problem in the past.

In addition, in the example shown in Fig. 1, the first assembly and the second
The capacitors (C ₂ ) 30, 35 and spark gaps 31, 36 in the assembly are shown in a staggered vertical relationship in the figure, but they are arranged in the same way, with the capacitors (C ₂ ) 30, 35 on the bottom and the spark gaps 31, 36 on the bottom. There is no change in the operating principle even if it is moved upward.

Similarly, even if the spark gaps 31 and 36 are placed at the bottom and the capacitors 30 and 35 are placed at the top, the electromagnetic waves generated by the first and second discharge assemblies are canceled out, resulting in low noise.

2 and 3 are cross-sectional views showing more detailed embodiments of the pulsed laser tube according to the present invention.

2 is a plane perpendicular to the optical axis, and FIG. 3 is a diagram cut along a plane including the optical axis (planes A and A' in FIG. 2).

The laser tube (laser gas container) 29 has insulator plates 39 and 4 above and below a metal or insulator frame 51.
It has a shape with a lid at 0.

The plate 39 is attached to the frame 51 by an appropriate number of screws 59, 60 via rubber packings 45A, 45B.
Similarly, the plate 40 has rubber packing 46A,
It is fixed to the frame 51 with screws 61 and 62 via 46B.

As shown in FIGS. 2 and 3, the anode 32 and cathode 33 forming the first discharge assembly ( ) are arranged parallel to the first optical axis of the laser gas container 29 . An anode 37 and a cathode 38 forming the second discharge assembly ( ) are provided parallel to the second optical axis of the laser gas container 29 . At the periphery of the plate 40 along the anode 32 forming the first discharge assembly, as shown in FIG.
An appropriate number (plurality) of capacitors 30 are provided.

Capacitor 30 is attached to metal plate 57 with screws 68 (see FIG. 2). The anode (A) 32 of the first discharge assembly () also has a plurality of screws 6
It is installed in 5.

A rod-shaped cathode (K) 33 extending in the optical axis direction is attached to the metal plate 55 with a plurality of screws 63, and a plurality of rods 54 are arranged along this cathode (K) 33. .

The metal plates 55 and 57 are feedthroughs 41 for a plurality of conductors and feedthroughs 4 for a plurality of conductors.
3 is screwed into the insulating plates 39 and 40, and supported so that the cathode (K) 33 and the anode (A) 32 face each other, and the tip of the rod 54 and the metal head 70 fixed to the capacitor 30 face each other. are doing.

The O-ring material 47 maintains airtightness between each feed through 41 and the plate 39, and the O-ring material 49 maintains airtightness between the feed through 43 and the plate 40.

As shown in FIG. 2, an appropriate number (plurality) of capacitors 35 are provided around the plate 39 along the anode 37 of the second discharge assembly (2).

Capacitor 35 is attached to metal plate 56 with screws 67. The anode (A) 37 of the second discharge assembly ( ) is similarly attached to the metal plate 56 with a plurality of screws 64 .

A rod-shaped cathode (K) 38 extending in the optical axis direction is attached to the metal plate 58 with a plurality of screws 66, and a plurality of rods 54B are arranged along this cathode (K) 38. There is.

Further, the metal plate 58 has a plurality of feed throughs 44.
Thus, the cathode (K) 38 and the anode (A) 37 are opposed to the insulating plate 40 and are supported so as to face the metal head 69 fixed to the tip of the rod 54B and the capacitor 35.

The O-ring material 48 maintains airtightness between the feed through 42 and the plate 39, and the O-ring material 50 maintains airtightness between the feed through 44 and the plate 40. A rectangular hole 52 made in the frame 51 and a rectangular hole 53 made in the frame 51 are a gas inlet and an outlet when the laser gas is caused to flow into the laser tube.

Although not shown in the figure, it is connected to an external gas circulator, gas cooler, etc. to keep the internal gas condition optimal so as not to degrade the laser oscillation characteristics when light pulses are repeatedly generated.

Next, the optical path will be explained with reference to FIG.

30 appearing in FIG. 3 is the capacitor of the first discharge assembly (), 32 is the anode (A) of the first discharge assembly (), and as mentioned above, the plate 57
Fixed. 70...70 are conductors forming one of the spark gaps 31...31 of the first discharge assembly ().

Similarly, 54B...54B is a conductor forming one of the spark gaps 36...36 of the second discharge assembly (), and is fixed to the metal plate 58 together with the cathode (K) 38.

Four holes 8 are formed in the part of the frame 51 that becomes the laser beam path.
0, 81, 82, 83 are provided, and the hole 80
A total reflection mirror 84 is installed corresponding to the hole, and quartz window plates 85, 86, 8 are installed in the other holes 81, 82, 83.
7 is attached.

The total reflection mirror 84 is connected to a case 88 that houses the reflection mirror via a rubber O-ring 93 to maintain airtightness, and the quartz window plates 85, 86, and 87 are connected to cases 89, 90, and 91 that house the window plates. They are each supported through rubber O-rings 95, 97, and 99 to maintain airtightness.

Reference numerals 100, 101, 102, and 103 are rings for fixing the reflecting mirror and the window plate to the cases 88, 89, 90, and 91.

Each case 88, 89, 90, 91 has rubber O-rings 92, 94, 9 to maintain airtightness, respectively.
6, 98, bolts 104, 105, 10
6,107 to be fixed to the frame 51.

The total reflection mirrors 108 and 109 form a resonator with the reflection mirror 84 and the window plate 87, and cause laser oscillation inside.
The laser light is emitted to the outside through the window plate 87. In the embodiment shown in FIG. 3, the light generated by the discharge between the two sets of anodes and cathodes is 1
It is extracted as a laser beam from the book.

In addition, by removing the total reflection mirrors 108 and 109,
By using one of 86 and 87 as a total reflection mirror and the other as a quartz plate, two parallel laser beams can be extracted in the same direction or in opposite directions.

In actual use (operation) of the laser tube, the external circuit and internal structure are connected to the feedthroughs 41, 42, 43, and 44 according to the wiring method shown in FIG.

FIG. 4 is a connection diagram showing still another embodiment of the pulsed laser tube according to the present invention.

Power supply (Vo) 21, Thyratron switch 24,
The basic functions of the charging resistor 22, coil 28, etc. of the capacitor (C ₁ ) 23 are the same as in the embodiment described above with reference to FIG.

Inside the laser tube 29, there are an anode (A) 32 and a cathode (K) 3 that form a first main discharge gap.
3. A first discharge assembly () consisting of a spark gap 31 and a second discharge assembly () consisting of an anode (A) 37, a cathode (K) 38 and a spark gap 39 forming a second main discharge gap are provided. The structure and operating principle are also the same as in the embodiment described above with reference to FIG.

However, the above embodiment and the first discharge assembly ()
capacitor (C ₂ ) 30 and second discharge assembly ()
The only difference is that the capacitor (C ₂ ) 35 is disposed outside the laser tube 29.

By arranging the capacitors (C ₂ ) 30 and 35 outside the tube, the length of the discharge circuit of the main discharge created by the anode, cathode, spark gap, and capacitor increases, the rise time of the discharge becomes longer, and the laser oscillation efficiency increases. The problem is that it gets worse.

However, since the contamination of the laser gas is reduced and the gas flow is no longer obstructed by the capacitor, the gas flow rate increases and the repetition characteristics of laser pulse emission can be improved.

(Modification) The present invention has been described above in detail using an excimer laser as an example.

A discharge type similar to an excimer laser,
That is, it is also effective for carbon gas lasers, nitrogen lasers, etc. that utilize atmospheric pressure discharge that requires preliminary ionization.

(Effects of the Invention) As explained above in detail, the pulsed laser according to the present invention is an excited discharge type pulsed laser, and has first and second discharge assemblies (), ( ), at least the discharge direction of the anode, cathode of the first assembly and the anode of the second assembly, the discharge direction of the cathode being opposite, or the discharge direction of the spark gap of the first assembly and the anode of the second assembly. The discharge directions of the spark gaps of the assemblies are reversed, and each assembly is configured to operate simultaneously.

Therefore, the electromagnetic waves generated by the discharge between the anode and cathode of each assembly cancel each other out, and the electromagnetic waves generated by the discharge between the spark gaps also cancel each other out.

If the discharge directions of the anode and cathode of each assembly are opposite and the direction of the spark gap is also opposite, both electromagnetic waves are canceled out.

According to the present invention, a low-noise excimer pulse laser can be realized.

This laser can be widely used in fields where excimer lasers are used that require low noise, such as medical sites where weak signals are often applied to living organisms, and production sites where computer-controlled machines are operated.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram for explaining the principle of a pulsed laser tube according to the present invention. FIG. 2 is a sectional view showing a more detailed embodiment of the pulsed laser tube according to the present invention, taken along a plane perpendicular to the optical axis. FIG. 3 is a sectional view showing a more detailed embodiment of the pulsed laser tube according to the present invention, taken along planes A and A' in FIG. 2. FIG. 4 is a schematic diagram for explaining another embodiment of a pulsed laser tube according to the present invention. FIG. 5 is a schematic diagram for explaining the operation of a conventional excimer laser device using discharge excitation. 21... Power supply (Vo), 22... Charging resistor, 2
3... Capacitor (C ₁ ), 24... Thyratron switch, 28... Charging coil (L), 29...
... Laser tube, 32 ... Anode (A) of the first discharge assembly, 33 ... Cathode (K) of the first discharge assembly,
30... 30... Other capacitor (C ₂ ) of the first discharge assembly, 31... Spark gap of the first discharge assembly, 37... Anode (A) of the second discharge assembly, 38... Second cathode (K) of the discharge assembly,
35... 35... Other capacitor (C ₂ ) of the second discharge assembly, 36... Spark gap of the second discharge assembly, 39, 40... Insulator plate, 41, 4
2, 43, 44...Feed through, 45A, 4
5B, 46A, 46B... Packing, 47, 4
8,49,50...O-ring, 51...frame, 5
2, 53... Gas hole provided in the frame, 55, 5
6, 57, 58...metal plate, 54A, 54B...
Metal rod (spark gap), 59, 60, 61,
62... Screw, 69, 70... Conductor (spark gap), 80, 81, 82, 83... Laser light passage hole, 84... Total reflection mirror, 85, 86, 87...
...Quartz window plate, 88...Case for housing the reflector, 89,90,91...Case for housing the quartz window plate, 92,~99...Rubber O-ring, 10
0,101,102,103... Fixed ring, 1
08,109... Total reflection mirror.

Claims (1)

[Scope of Claims] 1. By charging the charge charged in the capacitor through a switch element and through a spark gap in the laser tube to another capacitor for discharge excitation, and discharging the charge between the anode and the cathode through the spark gap. In a pulsed laser that performs laser oscillation, first and second discharge assemblies consisting of an anode, a cathode, a spark gap, and another capacitor are arranged at least in the direction of discharge of the anode and cathode of the first assembly and the anode of the second assembly. , the discharge direction of the cathode is opposite, or the discharge direction of the spark gap of the first assembly and the discharge direction of the spark gap of the second assembly are opposite, and each assembly is configured to be operated simultaneously. A pulsed laser tube featuring: 2. The pulsed laser tube according to claim 1, wherein the switch element is a thyratron. 3. The pulsed laser tube according to claim 1, wherein each set of capacitor and spark gap is connected in series within the discharge tube. 4. The pulsed laser tube according to claim 1, wherein each set of capacitors is arranged outside the discharge tube and connected in series with a spark gap arranged inside the discharge tube. 5. The pulsed laser tube according to claim 1, wherein the anode and cathode discharge directions of each assembly are opposite, and the spark gap discharge direction is also opposite.