JPH0426173A - Laser oscillation apparatus - Google Patents

Abstract

PURPOSE:To compound a plurality of wavelength-selected laser beams without using a dichroic mirror and without increasing a field strength inside an optical resonator by a method wherein a plurality of wavelength-selection optical systems which form the optical resonator together with a highly reflecting mirror are arranged so as to be faced by laying an optical axis between them. CONSTITUTION:When a laser beam L is generated, one part of the laser beam L is magnified by prisms 33a to 33c, 35a to 35c, is incident on diffraction gratings 34, 36 and is synchronized with laser beams L1, L2 at wavelengths lambda1, lambda2. The laser beams L1, L2 which have been synchronized by using the diffraction gratings 34, 36 are passed through the prisms 33c to 33a, 35c to 35a, a laser excitation part 21 and upper-side and lower-side apertures 26a, 26b in a regulation plate 27; they are reflected by a highly reflecting mirror 28; and they are returned to the laser excitation part 21. At this time, while the oscillated laser beams L1, L2 are being amplified by the laser excitation part 21, one part of them is deviated from an oscillation light path; it is turned to an optical axis O; and it is oscillated to the outside. That is to say, the laser beam L1 at the wavelength lambda1 and the laser beam L2 at the wavelength lambda2 are compounded around the optical axis O and are oscillated as a compounded laser beam LG between wavelength-selection optical systems 29, 31.

Description

Detailed Description of the Invention [Object of the Invention] (Industrial Application Field) The present invention relates to a laser oscillation device for combining and extracting a plurality of laser beams.

(Prior Art) For example, laser light having a plurality of wavelengths is sometimes used as an excitation light source for photoreaction.

Conventionally, laser light composed of a plurality of wavelengths has been obtained as shown in FIG.

That is, in the figure, 1 is a first laser excitation section such as an excimer gas laser, and 2 is a second laser excitation section. The first laser excitation section 1 is arranged within a first optical resonator 5 consisting of a first high reflection mirror 3 and a first partial reflection mirror 4, and the second laser excitation section 2 is arranged within a first optical resonator 5 consisting of a first high reflection mirror 3 and a first partial reflection mirror 4. It is arranged in a second optical resonator 8 consisting of a reflecting mirror 6 and a second partially reflecting mirror 7. A first wavelength selective optical element 9 such as an etalon is provided in the first optical resonator 5, and
Similarly, a second wavelength selective optical element 1] is provided within the second optical resonator 8.

The partial reflection mirror 4 of the first optical resonator 5 outputs a first laser beam whose wavelength is λ1 selected by the first wavelength selection element 9, and the upper second optical resonator 8 A second laser beam L2 having a wavelength of λ2 selected by the second wavelength selection element 11 is output from the partial reflection mirror 7. A dichroic mirror 12 is arranged on the optical path of the first laser beam L1 output from the first optical resonator 5 so as to be inclined at an angle of 45 degrees.

The first laser beam L1 passes through the dichroic mirror 12, and the second laser beam L2 is reflected by the dichroic mirror 12 and combined with the first laser beam L1.

Therefore, the laser beam L6 combined by the dichroic mirror 12 has two wavelengths, λ1 and λ2.

Note that the laser beams having wavelengths other than λ1 outputted from the first laser excitation section 1 are reflected by the dichroic mirror 12. Furthermore, the wavelength λ output from the second laser excitation unit 2
Laser beams other than 2 pass through the dichroic mirror 12 and are combined with laser beams of wavelengths other than λ from the first laser excitation section 1.

By the way, when the first laser beam with the wavelength λ and the second laser beam L2 with the wavelength λ2 are combined to form the two-wavelength laser beam LG in this way, the first laser beam, When the wavelengths λ1 and λ2 of and the second laser beam L2 are close to each other, the ability to transmit the first laser beam L1 with the wavelength λ and to reject the second laser beam L2 with the wavelength λ2. It becomes very difficult to manufacture a dichroic mirror 12 with this. Therefore, if the wavelengths of the two laser beams are close to each other in this way, it may not be possible to combine the two laser beams of different wavelengths using the dichroic mirror 12. Furthermore, since two laser excitation units 1.2 are required to obtain laser beams of two wavelengths, the configuration becomes complicated and large in size.

In addition, as a laser oscillation device with another configuration for obtaining laser light having two wavelengths, an optical resonator that can oscillate laser light of two wavelengths with one laser excitation part in between is provided. There is something I did. According to such a configuration, the configuration can be simplified compared to the case where two laser excitation units are used. However, since two laser beams with different wavelengths selected within one optical resonator are confined and amplified within the optical resonator, the electric field strength within the optical resonator increases, especially when the laser output If the output is increased, optical components such as an etalon provided in the optical resonator are likely to be damaged early, which may be impractical.

(Problem to be solved by the invention) In this way, when laser beams of different wavelengths output from two laser excitation units are combined using a dichroic mirror,
When the wavelengths of two laser beams are close to each other, it is very difficult to manufacture a dichroic mirror that can combine the laser beams, which is impractical, and the overall configuration becomes complicated. Furthermore, if one optical resonator is provided that can oscillate laser beams of two wavelengths by sandwiching one laser excitation section, the electric field strength within the optical resonator will increase. In some cases, optical components installed in the camera are easily damaged.

This invention was made based on the above circumstances, and its purpose is to transmit multiple laser beams whose wavelengths have been selected by multiple wavelength selection optical systems from one laser excitation unit without using a dichroic mirror. Moreover, it is an object of the present invention to provide a laser oscillation device 12 that can perform synthesis without increasing the electric field strength within an optical resonator.

[Structure of the Invention] (Means and Effects for Solving the Problems) In order to solve the above problems, the present invention provides a laser excitation section having a laser medium, and an excitation means for exciting the laser medium to generate laser light. a high-reflection mirror disposed opposite to one end of the laser excitation section along the optical axis direction of the laser beam generated in the laser excitation section, and a high reflection mirror disposed opposite to the optical axis at the other end of the laser excitation section. A plurality of wavelength selection optical systems are provided at positions facing each other with the optical axis in between, each forming an optical resonator with the high reflection mirror, and each optical resonator selects and amplifies a wavelength. Each laser beam is characterized by being output from each optical resonator to the outside along the optical axis.

With such a configuration, multiple laser beams whose wavelengths are selected and amplified in each optical resonator can be combined along the optical axis without using a dichroic mirror. Since the amplified laser light is extracted outside without being confined within the resonator, the laser light can be oscillated without increasing the electric field strength within each optical resonator.

(Embodiment) An embodiment of the present invention will be described below with reference to FIGS. 1 and 2. FIG. 1 shows a laser oscillation device such as an excimer laser, and this laser oscillation device is equipped with a laser excitation section 21. As shown in FIG. This laser excitation section 21 has transmission windows 2 on both end faces.
2a and 22b, and a discharge chamber 23 in which a gas laser medium is housed;
It is composed of a pair of main electrodes 24 which are arranged to face each other at a distance within the main electrodes 24, and a pre-ionization electrode (not shown) which pre-ionizes the discharge space prior to the main discharge between these main electrodes 24.

A high voltage power source 25 is connected to the main electrode 24, and electrical energy for main discharge is supplied from the high voltage power source 25.

When a main discharge is ignited between the pair of main electrodes 24 and the gas laser medium is excited, laser light is generated in a direction perpendicular to the direction of the discharge. The optical axis of the laser beam generated by this main discharge is defined as optical axis 0.

On one end surface side of the discharge gas chamber 23, a pair of apertures 26a and 26b are provided opposite to one transmission window 22a.
A regulation plate 27 having a perforation therein and a high reflection mirror 28 are arranged in this order. At a position facing the other transmission window 22b on the other end surface side of the discharge gas chamber 23, a first wavelength selection optical system 29 is arranged symmetrically with respect to the optical axis O at a position offset from the optical axis 0. and a second wavelength selection optical system 31
and are provided. The first wavelength selection optical system 29 forms a first optical resonator 32 with the high reflection mirror 28, and the second wavelength selection optical system 31 forms a second optical resonator with the high reflection mirror 28. 33 is formed.

In addition, a pair of apertures 2 bored in the regulation plate 27
6a and 26b are formed to be elongated along the width direction of the main electrode 24.

The first wavelength selection optical system 29 includes first to third prisms 33a to 33c and a first diffraction grating 34, and the second wavelength selection optical system 31 also includes fourth to sixth prisms 33a to 33c. It is composed of prisms 35a to 35c and a second diffraction grating 36. The first to third prisms 33a to 33C of the first wavelength selection optical system 29 have the optical axis O.
Similarly, the fourth to sixth prisms 35a to 35c of the second wavelength selection optical system 31 are arranged in a direction sequentially away from the optical axis 0.

These prisms 33a to 33c, 35a to 35
The first and second diffraction gratings 34 and 36, on which the laser light whose beam diameter has been expanded at c, are incident, have an angle of incidence of the laser light and a reflection angle of the tuned 1/- laser light (diffraction light). Retro-arranged so that they are equal. It is assumed that the wavelength of the first laser beam tuned by the first diffraction grating 34 is λ1, and the wavelength of the second laser beam L2 tuned by the second diffraction grating 36 is λ2.

Next, the operation of the laser oscillation device having the above configuration will be explained. First, when the high voltage power supply 25 is turned on, the backup type Mi? Electrical energy is supplied to the S pole and the main electrode 24, a discharge is generated at the pre-Qtla ionization electrode, and the discharge space between the pair of main electrodes 24 is pre-ionized. When the preliminary ionization of the discharge space progresses sufficiently, a main discharge is ignited between the pair of main electrodes 24 and the gas laser medium in the discharge chamber 23 is excited, thereby generating laser light.

When the laser beam is generated in this way, the oscillation of the laser beam starts in the first optical resonator 32 and the second optical resonator 33, respectively. That is, in the first optical resonator 32, a part of the laser beam is expanded by the first to third prisms 33a to 33c and enters the first diffraction grating 34, and the laser beam with the wavelength λ1 is generated. It is tuned to L1. 1st
The first laser beam tuned by the diffraction grating 34 passes through the prisms 33c to 33a, passes through the laser excitation section 21 and the aperture 26a above the regulation plate 27, is reflected by the high reflection mirror 28, and is laser-excited again. Return to part 21. In other words,
The first laser beam L1 with a wavelength λ1 has an optical axis 0 of the laser beam.
It is oscillated in an oscillation optical path that deviates from the oscillation path.

A part of the first laser beam of wavelength λ1 that follows such an oscillation optical path is amplified within the laser excitation unit 21 and is diffracted or refracted toward the direction where the electron density of the gas laser medium is high. Turn around in the direction of 0. Optical axis O
The first laser light that has turned around in the direction is deviated from the oscillation optical path of the first optical resonator 32, so it is oscillated to the outside along the optical axis O.

Similarly, in the second optical resonator 33, a part of the laser beam is expanded by the fourth to sixth prisms 35a to 35c and enters the second diffraction grating 36, and the second laser beam with the wavelength λ2 is generated. It is tuned to L2. The second laser beam L2 tuned by the second diffraction grating 36 is transmitted through the prisms 35 c to 3
5a, the laser beam passes through the aperture 26b below the laser excitation unit 21 and the regulation plate 27, is reflected by the high reflection mirror 28, returns to the laser excitation unit 21 again, and is oscillated in an oscillation optical path that deviates from the optical axis O of the laser beam. Ru. At that time, the first optical resonator 3
Similar to the laser beam L1 oscillated in 2, the laser excitation unit 21
While being amplified, part of the light deviates from the oscillation optical path of the first optical resonator 32, wraps around in the direction of the optical axis 0, and is oscillated to the outside. In other words, since the first laser beam with wavelength λ and the second laser beam L2 with wavelength λ2 are combined around the optical axis O, the combined laser beam with wavelengths λ1 and λ2 is The light L6 is oscillated from between the first and second wavelength selection optical systems 29 and 31.

FIG. 3 shows the oscillation spectrum of the synthesized laser beam. In other words, A in the figure represents synthetic laser light. is the oscillation gain curve of λ, and B is the wavelength λ tuned by the first optical resonator 32.
C shows the spectrum of the second laser light L2 of wavelength λ2 tuned by the second optical resonator 33.

If the combined laser beam LG having two wavelengths is obtained in this way, the laser beams of two wavelengths L2 can be combined without using a dichroic tsukumira, so the wavelengths of these laser beams L1 and L2 can be Even if they are close to each other, they can be synthesized without any problem.

Moreover, each optical resonator 32, 33 is not a closed type that confines and amplifies the laser beams Ll and L2 of the respective wavelengths inside, but is a so-called open type that takes out the amplified laser beams Ll and L2 to the outside. , the electric field strength inside the optical resonators 32 and 33 can be weakened without causing a decrease in the output of the laser beams Ll and L2. Therefore, the prisms 33a to 33C provided inside the optical resonators 32.33
There is no possibility of early deterioration of optical components such as 135a to 35c and the diffraction gratings 34 and 36.

Note that the present invention is not limited to the above-mentioned embodiment, and can be modified in various ways without departing from the spirit thereof. For example, the wavelengths of the laser beams LL2 tuned by the first optical resonator 32 and the second optical resonator 33 may be made to be the same. Single-wavelength laser light with a spectrum can be obtained.

Furthermore, if a pair of optical resonators are placed apart from each other in the width direction of the pair of main electrodes with the oscillation optical axis O as the center, laser beams that are synthesized as in the second embodiment shown in FIG. The LG can be formed into a flat shape that is elongated in the direction in which the pair of main electrodes 24 are separated.

Furthermore, if four optical resonators that tune the laser beam to different wavelengths are arranged at 90 degree intervals around the optical axis O, these optical resonators can be arranged as shown in the third embodiment shown in FIG. It is possible to synthesize laser beams L1 to L4 of four different wavelengths, wavelengths λ1 to λ4, which are tuned by the wavelengths λ1 to λ4. In this third embodiment, the four laser beams L1 to L4 may have the same wavelength.

Although the wavelength selection optical system is formed from a prism and a diffraction grating, an etalon plate, a birefringence filter, a prism dispersion optical system, or the like may be used. Further, the laser oscillation device is not limited to a gas laser, but may be a dye laser, a solid laser, or the like.

Further, the regulating plate 27 shown in the above embodiment is not necessarily necessary, and simultaneous oscillation control of multiple wavelengths is possible even without it.

[Effects of the Invention] As described above, the present invention is characterized in that a high-reflection mirror is disposed facing one end in the optical axis direction of the laser beam generated in the laser excitation section, and a high reflection mirror is disposed facing the other end in a position off the optical axis. A plurality of wavelength selection optical systems each forming an optical resonator with the above-mentioned high reflection mirror are arranged facing each other with this optical axis in between, and each optical resonator selects a wavelength and amplifies each laser beam. is caused to oscillate externally from each optical resonator along the optical axis.

Therefore, since the respective laser beams whose wavelengths are selected in each optical resonator are combined within the laser excitation section without using a dichroic mirror, even if the wavelengths of the respective laser beams are close to each other, Multiple laser beams can be combined without any problems. In addition, since the laser light that has been amplified after wavelength selection in each optical resonator is oscillated without being confined within the optical resonator, the electric field strength within the optical resonator increases and Optical components are not damaged prematurely.

[Brief explanation of the drawing]

Fig. 1 is a configuration diagram of a laser oscillation device showing an embodiment of the present invention, Fig. 2 is a sectional view taken along the line ■-■ in Fig. 1, and Fig. 3 similarly shows the spectrum of the synthesized laser light. line diagram,
FIGS. 4 and 5 are cross-sectional views showing the cross-sectional shape of combined laser beams showing other embodiments of the present invention, and FIG. 6 is a configuration diagram of a conventional laser oscillation device. 21... Laser excitation section, 24... Electrode (excitation means)
25... High voltage power supply (excitation means) 28... High reflection mirror 29... First wavelength selection optical system, 31...
Second wavelength selection optical system, 33a to 33C1a to 35C...prism, 29,...first and second diffraction gratings.

Claims (1)

[Claims] a laser excitation section having a laser medium; an excitation means for exciting the laser medium to generate laser light; The placed high reflection mirror and the high reflection mirror placed opposite to each other with the optical axis in between at a position off the optical axis on the other end side of the laser excitation section form an optical resonator, respectively. It is characterized in that it is equipped with a plurality of wavelength selection optical systems, and each laser beam that has been wavelength-selected and amplified in each optical resonator is outputted to the outside along the optical axis after leaving each optical resonator. Laser oscillation device.