JPH06334244A - Excimer laser oscillator - Google Patents

Abstract

PURPOSE:To provide an excimer laser oscillator equipped with an optical oscillator having simple structure which can be regulated easily to make uniform the intensity of beam. CONSTITUTION:The excimer laser oscillator comprises an optical oscillator 5 equipped with a total reflector 3 and a partial reflector 4 wherein an optical system 11 for flattening the intensity of laser beam is disposed on the optical path in the optical oscillator 5.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an excimer laser oscillator, and more particularly to an excimer laser oscillator capable of obtaining a laser beam having a uniform beam intensity distribution in a beam cross section.

[0002]

2. Description of the Related Art Generally, an excimer laser oscillator has a short upper level lifetime of a few nanoseconds and a high amplification efficiency as compared with other laser oscillators of different types, so that it tends to be a multimode oscillation. For this reason, the beam cross-section intensity of the laser beam emitted from the excimer laser oscillator is extremely nonuniform.

For example, a discharge excitation type excimer laser oscillator has a flat-top intensity distribution in the electrode direction and a Gaussian-like intensity distribution in the direction perpendicular to the electrodes.

An outline will be given based on FIGS. 4 to 6. Figure 4
FIG. 1 is a schematic perspective view of a general excimer laser oscillator 1. This excimer laser oscillator 1 includes a laser container 2 and a light having a total reflection mirror 3 and a partial reflection mirror 4 provided in front of and behind the laser container 2, respectively. And a resonator 5.

The laser vessel 2 contains a pair of discharge electrodes 6 and a gas medium for laser oscillation, and plasma is generated by the discharge between the discharge electrodes 6 to generate an optical resonator 5.
Laser oscillation is performed by.

Each of the pair of discharge electrodes 6 has a substantially semicircular cross section so as to generate a discharge state as uniform as possible between them, and has a length of 2L.

As shown in the figure, the length direction parallel to the top surface 6A of the discharge electrode 6 is the X axis (optical axis A), and the length of the discharge electrode 6 is in the plane including the pair of discharge electrodes 6. A direction passing through the direction center is defined as a Y axis, and a direction perpendicular to the length direction (optical axis A, X axis) of the discharge electrode 6 and the center direction (Y axis) is defined as a Z axis.

Between the discharge electrodes 6, the portion of the top surface 6A has the best discharge state, and therefore the beam intensity of the emitted laser beam is maximum from this portion. However, the actual beam intensity is measured outside the partial reflecting mirror 4, but for convenience of description, it will be described below based on the X axis, Y axis, and Z axis.

That is, as shown in FIG. 5, X of Z = 0
The beam intensity in the Y plane (the beam intensity as seen from the direction of the X axis when cut in the XY plane) is maximum, and the beam intensity becomes gradually weaker as it deviates in the positive and negative directions of Z from this (Gaussian-like Intensity distribution).

Further, as shown in FIG. 6, Y perpendicular to the X-axis is used.
The beam intensity in the Z plane (the beam intensity as seen from the X-axis direction when cut in the YZ plane) is maximum at the portion corresponding to the interval 2D between the top surfaces 6A of the discharge electrodes 6, from which the positive and negative Y directions are obtained. The beam intensity gradually weakens as it shifts in the direction (flat-top intensity distribution).

Therefore, in applying the oscillated laser beam to various applications, it is important to make the beam intensity distribution uniform, but the beam propagation direction is perpendicular to the beam propagation direction (direction between the electrodes and the beam). There is a problem that it is difficult to obtain a uniform beam intensity distribution (or flat top intensity distribution) in the direction perpendicular to the propagation direction; the Z-axis direction).

In order to eliminate such a beam intensity nonuniformity, conventionally, as shown in FIG. 7, an optical system 7 called a beam homogenizer is provided outside the optical resonator 5 of the excimer laser oscillator 1 (outside the partial reflecting mirror 3). ) Is being installed.

This beam homogenizer 7 combines a plurality of prisms, reflecting mirrors, lenses and the like to divide the beam into a plurality of beams, then superimposes the plurality of beams again, and integrates by superimposing the beams. This is intended to make the beam intensity uniform. Such a beam homogenizer is disclosed in, for example, JP-A-2-32.
No. 3, etc.

However, the conventional method has the following problems because the optical system such as the beam homogenizer 7 for uniformizing the beam intensity is installed outside the optical resonator 5 of the excimer laser oscillator 1.

That is, since the beams divided into a plurality of beams by the beam homogenizer 7 have different propagation directions, there is a problem that the divergence angle of the beams after superposition becomes large.

Further, when a plurality of divided beams are superposed, the range in which the beam intensity becomes uniform is narrow in the beam propagation direction, and there is a problem that the intensity distribution is not uniform before and after that range.

Further, the more uniform the beam intensity is, the more the number of beam divisions must be increased.
There is a problem that the configuration of the beam homogenizer 7 becomes complicated and its adjustment is difficult.

Moreover, since the beam homogenizer 7 is installed outside the optical resonator 5, it is necessary to adjust the optical resonator 5 and the beam homogenizer 7 independently.
There is a problem that the adjustment work requires double labor.

Furthermore, the beam homogenizer 7 generally has a complicated structure. By installing such an optical system outside the optical resonator 5, the beam propagation efficiency is lowered and the laser energy is effectively utilized. There is a problem that you can not.

[0020]

SUMMARY OF THE INVENTION The present invention has been made in consideration of the above problems, and solves the above problems with a simple structure and makes the beam intensity uniform, which is easy to adjust. An object of the present invention is to provide an excimer laser oscillator provided with an optical resonator that can be used.

[0021]

That is, the present invention focuses on arranging a beam homogenizing optical system not on the outside of the optical resonator but on the optical path inside the optical resonator. An excimer laser oscillator having an optical resonator provided with a mirror, characterized in that a beam homogenizing optical system capable of flattening a laser beam intensity is arranged on an optical path in the optical resonator. It is an oscillator.

The beam homogenizing optical system can be arranged on the side of the partial reflecting mirror.

The beam homogenizing optical system can be constructed by combining a plurality of cylindrical lenses.

Each of the cylindrical lenses can be arranged in the length direction in parallel with a plane including the pair of discharge electrodes of the excimer laser.

The beam homogenizing optical system may be constructed by combining a plurality of aspherical lenses.

A position / tilt adjusting mechanism capable of adjusting the position and tilt of the beam uniformizing optical system with respect to the optical axis can be provided.

[0027]

In the excimer laser oscillator according to the present invention, since the beam homogenizing optical system is arranged on the optical path in the optical resonator, the optical homogenizer and other optical systems are installed outside the optical resonator. The problem can be solved, and the beam intensity can be made uniform by the flattening action of the laser beam by the beam uniformizing optical system.

Further, it becomes possible to make the beam uniform by adjusting the beam homogenizing optical system together with the optical resonator consisting of the total reflection mirror and the partial reflection mirror, and at the same time making the beam uniform. The adjustment work of the optical system can be simplified.

[0029]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, an excimer laser oscillator 10 according to a first embodiment of the present invention will be described with reference to the drawings. However, in the following description, the same parts as those in FIGS. 4 to 7 are designated by the same reference numerals, and the detailed description thereof will be omitted.

FIG. 1 shows the excimer laser oscillator 10 described above.
5 is a schematic configuration diagram showing the above-mentioned Y based on FIG.
It is the figure seen from the axial direction. The excimer laser oscillator 10 includes a laser container 2, an optical resonator 5 having a total reflection mirror 3 and a partial reflection mirror 4, and a beam homogenizing optical system 11.
Have and.

The beam homogenizing optical system 11 is a combination of a cylindrical lens perpendicular to the optical axis A, for example, a cylindrical concave lens 12 and a cylindrical convex lens 13.

The cylindrical concave lens 12 and the cylindrical convex lens 13 are arranged in parallel with the plane (XY plane) including the pair of discharge electrodes 6 in FIG. 4 in the length direction (Y direction perpendicular to the paper surface).

Incidentally, the cylindrical concave lens 12 and the cylindrical convex lens 13 of the beam homogenizing optical system 11.
There is provided a position / tilt adjusting mechanism 14 capable of adjusting the tilt and displacement of the optical axis A with respect to the optical axis A.

The operation of the excimer laser oscillator 10 will be described below. The beam emitted from the laser container 2 is incident on the beam uniformizing optical system 11. The beam width of the incident beam is expanded by the cylindrical concave lens 12 and condensed by the cylindrical convex lens 13 to become a beam parallel to the optical axis A, and returns to the laser container 2 and the total reflection mirror 3 side to make the beam uniform. And laser oscillation occurs.

Moreover, since the beam homogenizing optical system 11 is installed inside the optical resonator 5, when the position / tilt adjusting mechanism 14 or the like fails to adjust the optical axis A, laser oscillation does not occur and the opposite is said. Then, if the optical axis is adjusted so as to cause laser oscillation, a uniform beam can be obtained only by this adjustment work.

FIG. 2 and FIG. 3 are enlarged schematic views of the essential part of the excimer laser oscillator 20 according to the second embodiment of the present invention, in which the excimer laser oscillator 20 has a combination of aspherical lenses.

That is, the excimer laser oscillator 20
Is a beam homogenizing optical system (parallel light beam conversion unit) 21,
A pair of aspherical concave lens 22 and aspherical convex lens 23 are provided between the partial reflecting mirror 4 and the laser container 2.

In the excimer laser oscillator 20 having such a configuration, the incident beam B incident from the left side, that is, from the laser container 2 side is expanded in beam width by the aspherical concave lens 22, passes through the aspherical convex lens 23, and is thereby condensed. And is converted into a flat beam F having a uniform beam intensity profile.

Thus, accurate alignment is established between the beam homogenizing optical system 21 and the optical resonator 5, and the flat beam F is partially reflected by the partial reflecting mirror 4 and is directed toward the total reflecting mirror 3 side. Return, laser oscillation occurs.

FIG. 3 shows the case where this beam homogenization does not occur. The adjustment by the position / tilt adjusting mechanism 14 is insufficient, and the incident beam B passes through the aspherical concave lens 22 and is properly adjusted by the aspherical convex lens 23. If it is not made uniform, the reflection by the partial reflecting mirror 4 is not properly performed, and eventually laser oscillation does not occur.

That is, as shown by the broken line in the figure, when the alignment is out of alignment, the broken beam B1 does not return to the total reflection mirror 3 even if it is reflected by the partial reflection mirror 4, and the optical resonator 5 Cannot be configured.

In short, when the adjustment of the beam homogenizing optical system 21 with respect to the optical axis A is not successful, laser oscillation does not occur, and conversely, if the optical axis adjustment is performed so as to cause laser oscillation, only this adjustment work is required. A uniform beam can be obtained.

Therefore, by adjusting the optical axis so as to oscillate the laser without separately adjusting the laser and the beam homogenizer as in the conventional case, a uniform beam can be obtained.

In each of the embodiments shown in FIGS. 1 to 3, a so-called external resonance type in which the optical resonator 5 is installed outside the laser container 2 is shown. For the so-called internal resonance type in which the device 5 is installed, the beam homogenizing optical systems 11 and 21 are also provided.
It is possible to expect the same operational effect by disposing the above in front of the partial reflecting mirror 4.

[0045]

As described above, according to the present invention, by disposing the beam homogenizing optical system inside the optical resonator of the excimer laser oscillator, the excimer laser oscillator can be simply adjusted so as to perform laser oscillation. The beam intensity of the outgoing beam from can be made uniform.

[0046]

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram of an excimer laser oscillator 10 according to a first embodiment of the present invention.

FIG. 2 is an enlarged schematic configuration diagram of essential parts of an excimer laser oscillator 20 according to a second embodiment of the present invention.

FIG. 3 is an enlarged schematic configuration diagram of an essential part of the excimer laser oscillator 20 showing a case where beam homogenization does not occur.

FIG. 4 is a schematic perspective view of a conventional excimer laser oscillator 1.

FIG. 5 is a graph of beam intensity on an XY plane in the Z-axis direction.

FIG. 6 is a graph of beam intensity on the YZ plane in the X-axis direction.

FIG. 7 is a schematic configuration diagram showing a configuration in which the beam homogenizer 7 is installed outside the optical resonator 5 of the excimer laser oscillator 1 (outside the partial reflecting mirror 3).

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Excimer laser oscillator 2 Laser container 3 Total reflection mirror 4 Partial reflection mirror 5 Optical resonator 6 A pair of discharge electrodes 6A A top surface of a pair of discharge electrodes 7 An optical system called a beam homogenizer 10 Excimer laser oscillator 11 Beam homogenization optical system 12 Cylindrical concave lens 13 Cylindrical convex lens 14 Position / tilt adjusting mechanism 20 Excimer laser oscillator 21 Beam homogenizing optical system 22 Aspherical concave lens 23 Aspherical convex lens A Optical axis B Incident beam B1 Out of alignment F Beam flat beam 2L Discharge electrode 6 Length of 2D Spacing between top surfaces 6A of discharge electrode 6

Claims (6)

[Claims] 1. An excimer laser oscillator having an optical resonator having a total reflection mirror and a partial reflection mirror, the beam homogenizing optics capable of flattening a laser beam intensity on an optical path in the optical resonator. An excimer laser oscillator characterized by arranging a system. 2. The excimer laser oscillator according to claim 1, wherein the beam homogenizing optical system is arranged on the side of the partial reflecting mirror. 3. The excimer laser oscillator according to claim 1, wherein the beam homogenizing optical system is configured by combining a plurality of cylindrical lenses. 4. The excimer laser oscillator according to claim 3, wherein each of the cylindrical lenses has a length direction arranged in parallel with a plane including a pair of discharge electrodes of the excimer laser. 5. The excimer laser oscillator according to claim 1, wherein the beam homogenizing optical system is configured by combining a plurality of aspherical lenses. 6. The excimer laser oscillator according to claim 1, further comprising a position / tilt adjusting mechanism capable of adjusting the position and tilt of the beam uniformizing optical system with respect to the optical axis.