JPH03150884A - Narrow band laser device - Google Patents

Abstract

PURPOSE:To output a laser light narrowed in its band without absorption or scattering by disposing a high reflection mirror at one end side of a laser exciter, and disposing a prism for diffracting part of the laser light to the other end side and returning it into an optical resonator. CONSTITUTION:A high reflection mirror 34 is disposed at one end side opposed to one window 32a of a laser exciter 31 through a control member 33, a prism 35 and a diffraction grating 36 of a band narrowing element for forming an optical resonator of the mirror 34 are sequentially disposed at the other end side. A laser light L generated at the exciter 31 is diffracted by the prism 35, enlarged, reflected on the grating 36 to be narrowed, returned to the exciter 31, reflected on the mirror 34 through the slit 33a of the member 33, introduced into the exciter 31 at a predetermined enlarging angle, amplified, and then emitted from the other window member 32b. Thus, loss due to the absorption, scattering of the light L narrowed in its band can substantially be eliminated.

Description

Detailed Description of the Invention [Object of the Invention] (Industrial Application Field) The present invention relates to a narrowband laser device for narrowing the band of laser light.

(Prior Art) For example, some narrowband laser devices such as excimer lasers use a self-amplifying resonator in order to efficiently extract narrowband laser light. In other words, the laser beam generated in the laser excitation section is band-narrowed by an optical resonator including a band-narrowing element, and then the laser beam is reflected by a reflecting mirror and made to enter another part of the laser excitation section.
This allows it to be amplified and extracted. With such a self-amplifying narrowband laser device, it is possible to obtain several times the output.

Conventionally, as such a self-amplifying laser device, the fourth
It was constructed as shown in FIG. That is, in FIG. 4, reference numeral 1 indicates a laser excitation section such as an excimer laser.

This laser excitation section 1 consists of a gas laser medium (not shown) and excitation means for the gas laser medium. A first etalon 2 as a band-narrowing element and a first high-reflection mirror 3 are sequentially arranged on one end side of the laser excitation unit 1, and a second etalon 2 as a band-narrowing element is placed on the other end side. etalon 4 and diffraction grating 5 are arranged in sequence. Incidentally, the divergence angle of the laser light incident on the first and second etalons 2.4 is regulated by a regulating member 6 in which a slit 6a is formed, respectively.

A second high-reflection mirror 7 is arranged in a direction in which light of a predetermined wavelength out of the laser light reflected by the diffraction grating 5 is reflected. The laser beam reflected by the second high-reflection mirror 7 is expanded in beam diameter by a beam expander 11 consisting of a concave lens 8 and a convex lens 9, and returned to a different part of the laser excitation unit 1, where it is amplified. The laser beam is outputted from one end of the laser excitation section 1.

However, according to such a configuration, the narrowband laser light is outputted through many optical components such as the second cavity reflecting mirror 7, the concave lens 8, and the convex lens 9. Therefore, the laser light is absorbed and scattered by these optical components, which not only increases the loss but also causes the output laser light to include scattered light.

In the narrow band laser device shown in FIG. 5, an output mirror 21 is arranged at one end of the laser excitation section 1, and a prism 22 and a diffraction grating 23 as a band narrowing element are arranged at the other end. Further, upper slits 24 are provided at both ends of the laser excitation section 1, respectively.
A regulating member 24 having a lower slit 24b and a lower slit 24b is disposed.

The laser light generated in the laser excitation section 1 passes through the upper slit 24a of one of the regulating members 24 disposed on the other end side of the laser excitation section 1, is magnified by the prism 22, enters the diffraction grating 23, and enters the diffraction grating 23. Only light of a predetermined wavelength is reflected in the same direction as the incident direction. Then, the light passes through the upper slit 24a of the regulating member 24 and the upper slit 24a of the other regulating member 24, and is output from the output mirror 21.

The narrow band laser beam outputted 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 is transmitted to the laser excitation section 1. Inject it into a different part than before. Thereby, the laser light is amplified and output from the lower slit 24b of the other regulating member 24.

However, according to such a configuration, the narrowband laser light passes through the output mirror 21 or is reflected by the first to third reflection mirrors 25a to 25c and is output, so that the laser beam shown in FIG. Similar to the laser device described above, absorption and scattering occur in the output mirror 21 and reflection mirrors 25a to 25c,
Not only does the loss increase, but the output laser light also includes scattered light. Moreover, a plurality of reflecting mirrors 25
A to 25c must be used, which may lead to misalignment of the optical axis or reduced maintainability.

(Three problems to be solved by the invention) As described above, in the conventional narrowband laser device that self-amplifies the laser beam by returning it to the laser excitation part and passing it through, in order to output a narrowband laser beam, Because the laser beam has to pass through many optical components, the laser beam may be absorbed or scattered by these optical components, resulting in large losses, and the output laser beam may include scattered light. Something happened.

This invention was made based on the above circumstances, and its purpose is to output narrow band laser light without using many optical components that cause absorption and scattering of the laser light. An object of the present invention is to provide a narrowband laser device that enables the following.

[Structure of the Invention] (Means and Effects for Solving the Problems) In order to solve the above problems, the present invention provides a narrowband laser comprising an optical resonator and a laser excitation provided in the optical resonator. In the apparatus, the optical resonator is disposed on one end side of the laser excitation section, and the optical resonator is provided on one end side of the laser excitation section, and a predetermined beam is reflected by the high reflection mirror toward the one end side of the laser excitation section. A prism is arranged to reflect at a divergence angle, refract only a part of the laser beam, and return it into the optical resonator.

According to such a configuration, the laser beam narrowed by the band-narrowing element and extracted to the outside is only reflected by one high-reflection mirror, and is not reflected by other optical components or transmitted. Absorption and scattering are less likely to occur.

(Example) Hereinafter, a first example of the present invention will be described with reference to FIG. In the figure, numeral 31 is a laser excitation section such as an excimer laser. This laser excitation section 31 includes a gas laser medium (not shown) and excitation means for exciting the gas laser medium.

Windows 32a132b are provided at both ends of the laser excitation section 31, respectively.
is formed. One window 31a of the laser excitation section 31
A mirror reflection mirror 34 is disposed at one end opposite to the above-mentioned high reflection mirror 34 via a regulating member 33 in which a slit 33a is formed, and a prism 35 and a band narrowing element are disposed at the other end. Diffraction gratings 36 forming an optical resonator are sequentially arranged.

The laser beam generated by the laser excitation section 31 is refracted and expanded by the prism 35, and then enters the diffraction grating 36. This diffraction grating 36 is arranged at an angle where the angle of incidence and angle of reflection are equal for light of a predetermined wavelength. Thereby, the laser beam generated in the laser excitation section 31 and reflected by the diffraction grating 36 to have a narrow band returns to the inside of the laser excitation section 31 .

The narrow band laser beam passes through the slit 33 of the regulating member 33.
a, is reflected by the high-reflection mirror 34, passes through the slit 33a again, enters the laser excitation unit 31 at a predetermined divergence angle, is amplified, and is emitted from the other window 32b. The prism 35 is arranged so as to refract only a part of the laser light emitted from the other window 32b and guide it to the diffraction grating 36. The laser light that is emitted from the other window 32b and does not enter 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 beam generated in the laser excitation section 31 is 5 mm x 20 mm, the width dimension of the slit 33a of the regulating member 33 is 211%, and the spread angle of the laser beam passing through this slit 33a is 3 mrads.
If the prism 35 is placed 1 m away from the slit 33a, the cross-sectional shape of the laser beam at the position of the prism 35 is 5 mm x 20 mm. Therefore, of the 5 mm width of this laser beam, this pre-arrangement is made so that the upper part 21 in the width direction in FIG. 1 is incident on the prism 35.

By arranging the diaphragm 35, the lower portion 31 in the width direction can be outputted to the outside.

Note that the dimension of 20 m5 in the cross-sectional shape of the laser beam is determined by the gap length between a pair of discharge electrodes (not shown) serving as excitation means.

According to the narrowband laser device having such a configuration, the laser beam is refracted and expanded by the prism 35 and enters the diffraction grating 36, and the laser beam narrowed here is reflected by the high reflection mirror 34 and sent to the laser excitation section 31. It is amplified by entering the beam again.

On the other hand, it is reflected by the high reflection mirror 34, passes through the slit 33a of the regulating member 33, and spreads at a predetermined angle to the other window 32.
Only a part of the laser light emitted from b enters the prism 35, and the rest is taken out as an output. Therefore, after the laser beam is narrow-banded, it is simply reflected by the high-reflection mirror 34 and taken out to the outside (outside the optical path of the optical resonator), and there is no possibility of it being reflected by other optical components or passing through. Therefore, there is almost no loss due to absorption or scattering in optical components, and the output laser light does not include scattered light.

FIG. 2 shows a second embodiment of the present invention, in which an etalon 41 is used as the band narrowing element instead of the diffraction grating 36, and the etalon 41 is connected to the prism 3.
5 is installed at a position where the magnified laser beam is incident, and a high reflection mirror 42 is installed opposite to this etalon 41.
The etalon 41 is arranged by this high reflection mirror 42.
The narrowband laser beam is returned to the laser excitation section 31 via a prism 35.

Even in this configuration, the narrow band laser beam can be extracted without being absorbed or scattered by optical components, as in the first embodiment.

FIG. 3 shows a third embodiment of the present invention, which is the same as the second embodiment in that an etalon 41 is used as a band narrowing element, but the etalon 41 is connected to the regulating member 3.
3, and this regulating member 33:; High reflection mirror 34 facing
The second embodiment differs from the second embodiment in that it is arranged between the two.

Even in such a configuration, laser light can be extracted without being absorbed or scattered by optical components.

In each of the above embodiments, examples were given in which the present invention was applied to an excimer laser, but the present invention can also be applied to other laser devices, such as a CO2 laser.

[Effects of the Invention] As described above, the present invention has the advantage that the laser light whose band has been narrowed by the band narrowing element is not reflected or transmitted by many optical components (because it is taken out, it is not caused by absorption or scattering). Not only is there almost no loss, the output laser light does not contain scattered light.Furthermore, since fewer optical parts are used, optical axis alignment and maintainability can be improved.

[Brief explanation of the drawing]

FIG. 1 is a configuration diagram of a laser device showing a first embodiment of the invention, FIG. 2 is a configuration diagram of a laser device also showing a second embodiment of the invention, and FIG. Embodiment 3 is a configuration diagram of a laser device showing the third embodiment, and FIGS. 4 and 5 are configuration diagrams of conventional laser devices. 31... Laser excitation unit, 34... High reflection mirror (optical resonator), 35... Prism, 36... Diffraction grating (
band narrowing element), 41... etalon (band narrowing element)
.

Claims (1)

[Claims] A narrowband laser device comprising an optical resonator, a laser excitation section provided within the optical resonator, and a means for narrowing the band of laser light generated in the laser excitation section and outputting the narrow band to the outside of the laser excitation section. A high reflection mirror forming the optical resonator is disposed at one end of the laser excitation section, and a high reflection mirror forming the optical resonator is disposed at the other end, and a beam is reflected by the high reflection mirror toward the one end of the laser excitation section. 1. A narrow band laser device characterized in that a prism is disposed to refract only a part of a laser beam traveling at a divergence angle and return it into the optical resonator.