JPH0797671B2 - Narrow band laser device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Field of Industrial Application) The present invention relates to a narrow band laser device for narrowing the band of laser light.

(Prior Art) For example, in a narrow band laser device such as an excimer laser, there is a narrow band laser device in which a self-amplifying resonator is used in order to efficiently extract a narrow band laser beam. That is, after narrowing the band of the laser light generated in the laser pumping section by the optical resonator including the band-narrowing element, the laser light is folded back by the reflecting mirror and is incident on the other part of the laser pumping section, and It is amplified and taken out. According to such a self-amplification type narrow band laser device, it is possible to obtain an output several times higher.

Conventionally, such a self-amplification type laser device is the third
It was constructed as shown in the figure or FIG. That is, in FIG. 3, reference numeral 1 in the drawing denotes a laser pumping unit such as an excimer laser. The laser pumping section 1 comprises a gas laser medium (not shown) and pumping means for the gas laser medium. A first etalon 2 as a band narrowing element and a first high reflection mirror 3 are provided on one end side of the laser pumping section 1.
Are sequentially arranged, and the second etalon 4 and the diffraction grating 5 as the band narrowing element are sequentially arranged at the other end side. The laser light L incident on the first and second etalons 2 and 4 has a restricting member 6 in which a slit 6a is formed.
The divergence angle is regulated by.

A second high-reflecting mirror 7 is arranged in a direction in which light of a predetermined wavelength is reflected in the laser light L reflected by the diffraction grating 5. The laser beam L reflected by the second high-reflecting mirror 7 has its beam diameter expanded by a beam expander 11 composed of a concave lens 8 and a convex lens 9 and is returned to a portion different from the former portion of the laser pumping section 1, where it is amplified. Then, the laser excitation part 1 is configured to output from one end side thereof.

However, according to such a configuration, the laser beam L having a narrow band is output through many optical components such as the second high reflection mirror 7, the concave lens 8 and the convex lens 9. Therefore, the laser light L is absorbed or scattered by these optical components, resulting in a large loss, and the output laser light L may include scattered light.

In the narrow band laser device shown in FIG. 4, an output mirror 21 is arranged on one end side of the laser pumping section 1, and a prism 22 and a diffraction grating 23 as a narrow band element are arranged on the other end side. Further, a regulating member 24 having an upper slit 24a and a lower slit 24b is arranged at both ends of the laser excitation unit 1, respectively.

The laser beam L generated by the laser pumping section 1 passes through the upper slit 24a of the one regulating member 24 arranged on the other end side of the laser pumping section 1 and is expanded by the prism 22 so that the diffraction grating 2
Light of a predetermined wavelength is reflected in the same direction as the incident direction. Then, the light is output from the output mirror 21 through the upper slit 24a of the regulating member 24, the laser excitation unit 1 and the upper slit 24a of the other regulating member 24.

The laser beam L that has been narrowed and output from the output mirror 21 is sequentially reflected by the first to third reflecting mirrors 25a to 25c, passes through the lower slit 24b of the other regulating member 24, and the laser pumping unit 1 described above. It is incident on a part different from the previous one. As a result, the laser light L is amplified and output from the lower slit 24b of the other regulating member 24.

However, according to such a configuration, the laser beam L whose band has been narrowed passes through the output mirror 21 or is reflected by the first to third reflecting mirrors 25a to 25c and is output. Similar to the laser device shown, absorption and scattering occur at the output mirror 21 and the reflection mirrors 25a to 25c, the loss increases, and the output laser light L includes scattered light. Moreover, since a plurality of reflection mirrors 25a to 25c must be used, deviation of the optical axis may occur and maintainability may deteriorate.

(Problems to be Solved by the Invention) As described above, in the conventional narrowband laser device that self-amplifies by returning the laser light to the laser pumping portion and passing the laser light, in order to output the narrowed laser light. Since many optical components have to pass through, laser light is absorbed or scattered by these optical components, resulting in a large loss, and the output laser light contains scattered light. I had a problem.

The present invention has been made in view of the above circumstances, and an object thereof is to output a laser beam having a narrow band without using many optical components that cause absorption or scattering of the laser beam. Another object of the present invention is to provide a narrow band laser device capable of performing the above.

[Structure of the Invention] (Means and Actions for Solving the Problems) In order to solve the above problems, the present invention is directed to a laser pumping section containing a laser medium and an optical axis of a laser beam generated by the laser pumping section. With a high-reflection mirror arranged to face one end side of the laser pumping section, and of the laser light traveling at a predetermined divergence angle reflected by the high-reflection mirror arranged on the other end side of the laser pumping section A first means provided to be inserted into a part of the beam cross section for splitting the laser light; and a second means for narrowing the bandwidth of the laser light split by the first means and returning it to the laser pumping section. Is provided.

With such a configuration, the number of optical components that reflect or transmit the laser light that has been narrowed by the second means and is extracted to the outside is smaller than in the conventional case, so that absorption and scattering are less likely to occur. .

(Embodiment) Hereinafter, a first embodiment of the present invention will be described with reference to FIG. In the figure, reference numeral 31 is a laser excitation unit such as an excimer laser. The laser pumping section 31 comprises a gas laser medium (not shown) and pumping means for pumping the gas laser medium. A window 32 is provided at each end of the laser excitation unit 31.
a and 32b are formed. One window 31 of the laser excitation unit 31
A high-reflecting mirror 34 is arranged on one end side opposite to a through a restricting member 33 having a slit 33a, and a prism 35 and a band narrowing element are provided on the other end side. The diffraction gratings 36 forming the optical resonator are sequentially arranged.

The laser light L generated by the laser pumping section 31 is refracted and expanded by the prism 35 and is incident on the diffraction grating 36.
The diffraction grating 36 is arranged at an angle where the incident angle and the reflection angle are equal to each other with respect to the light having a predetermined wavelength. Thereby, after being generated in the laser excitation unit 31, the diffraction grating
The laser beam L reflected by 36 and narrowed in bandwidth is emitted by the laser excitation unit.
Return to 31.

That is, in this embodiment, the diffraction grating 36 is the laser excitation part 31.
The second means also serves as a narrowing means for narrowing a part of the laser light L generated in 1) and a returning means for returning the narrowed laser light L to the prism 35.

The narrowed laser beam passes through the slit 33a of the regulation member 33 and is reflected by the high reflection mirror 34, and again the slit 33a.
After being amplified by being incident on the inside of the laser excitation part 31 at a predetermined divergence angle, the light is emitted from the other window 32b.
The prism 35 is arranged so as to refract only a part of the laser light L emitted from the other window 32b and guide it to the diffraction grating 36. The laser light L emitted from the other window 32b and not incident on the prism 35 is taken out as an output to the outside of the optical resonator.

The size of the cross-sectional shape of the laser light L generated by the laser excitation unit 31 is 5 mm × 20 mm, the width dimension of the slit 33a of the regulating member 33 is 2 mm, and the spread angle of the laser light L passing through this slit 33a is
Assuming that the prism 35 is placed 3 mrad away from the slit 33a by 1 m, the sectional shape of the laser light L at the position of the prism 35 is 5 mm × 20 mm. Therefore,
If the prism 35 is arranged such that the 2 mm portion on the upper side in the width direction in FIG. 1 of the laser beam L is incident on the prism 35, the 3 mm portion on the lower side in the width direction is exposed to the outside. Can be output to.

The size of 20 mm in the cross-sectional shape of the laser beam L is determined by the gap length of a pair of discharge electrodes (not shown) serving as excitation means.

According to the narrow band laser device having such a configuration, the prism
The laser beam L refracted and expanded by 35 is incident on the diffraction grating 36, and the narrowed laser beam L is reflected by the high-reflecting mirror 34 and is incident on the laser excitation section 31 again to be amplified.

On the other hand, the laser light L reflected by the high-reflecting mirror 34, passing through the slit 33a of the regulating member 33 and emitted from the other window 32b at a predetermined divergence angle, is incident on the prism 35 only partially, and the rest is left. It will be taken out as an output. Therefore, the laser beam L is taken out to the outside (outside the optical path of the optical resonator) only by being reflected by the high-reflecting mirror 34 after being narrowed in band, and reflected or passed by other optical parts. Therefore, there is almost no loss due to absorption or scattering in the optical component, and the output laser light L does not include scattered light.

Further, since only the laser light L split by the prism 35 is incident on the diffraction grating 36 to narrow the band, the diffraction grating 36
The amount of the laser light L that irradiates 36 is reduced. As a result, the life of the diffraction grating 36 can be extended.

FIG. 2 shows a second embodiment of the present invention in which an etalon 41 is used as a band-narrowing element instead of the diffraction grating 36, and the etalon 41 is expanded by a prism 35. Installed at the position where the light L enters,
A high-reflecting mirror 42 is arranged so as to face the etalon 41, and the laser beam L narrowed by the etalon 41 by the high-reflecting mirror 42 is returned to the laser excitation unit 31 via a prism 35. .

That is, in this embodiment, the etalon 41 constitutes the band narrowing means, the high reflection mirror 42 constitutes the folding means, and these two constitute the second means.

Even in such a configuration, the laser beam L whose band has been narrowed can be taken out without being absorbed or scattered by the optical component as in the first embodiment.

In each of the above-described embodiments, the example applied to the excimer laser is given, but the present invention can be applied to other laser devices such as other lasers such as CO ₂ laser.

[Advantages of the Invention] As described above, according to the present invention, the laser beam narrowed by the second means is extracted without being reflected by or transmitted through many optical components. In addition, the output laser light does not contain scattered light. In addition, since the number of optical components used is small, the alignment of the optical axis and the maintainability can be improved.

Further, since only the laser light split by the first means is made incident on the second means, the amount of light emitted from the second means is reduced, and the life can be extended.

[Brief description of drawings]

1 is a block diagram of a laser device showing a first embodiment of the present invention, FIG. 2 is a block diagram of a laser device showing a second embodiment of the present invention, and FIGS. 3 and 4 are respectively It is a block diagram of the conventional laser apparatus. 31 …… Laser excitation part, 34 …… High-reflection mirror (optical resonator), 35 …… Prism, 36 …… Diffraction grating (narrowing element), 41 …… Etalon (narrowing element).

Claims (2)

[Claims] 1. A laser pumping section containing a laser medium, a high-reflecting mirror arranged to face one end of the laser pumping section on the optical axis of laser light generated by the laser pumping section, and the laser. First means for dividing the laser beam, which is disposed on the other end side of the excitation unit and is inserted into a part of the beam cross section of the laser beam which is reflected by the high reflection mirror and advances at a predetermined divergence angle; And a second means for narrowing the band of the laser light split by the first means and returning the narrowed laser light to the laser pumping section. 2. The second means comprises narrowing means for narrowing the laser light and returning means for returning the laser light narrowed by the narrowing means to the laser pumping section. The narrow band laser device according to claim 1, wherein