JPH03261191A - Laser amplifying system - Google Patents

Abstract

PURPOSE:To suppress loss of amplified energy due to ASE by disposing a spatial filter having a pinhole between a laser oscillator stage and a laser amplifier stage. CONSTITUTION:Since a laser beam 5 contains a spontaneously emitted light from each laser oscillation tube 2, referred to ASE 10 (Amplified Spontaneous Emission), a high quality beam having high convergence and small spot diameter can be obtained when the laser beam 5 is converged through a lens 11 and the like, but the ASE has a low convergence. Consequently, a pinhole 12 is arranged at the converging point(focus) of the high quality beam in order to eliminate the ASE and to pass only the high quality beam through the pinhole 12, and then the high quality beam is recovered to a parallel beam through a convex lens 11a arranged symmetrically. Consequently, energy loss can be suppressed when a laser beam containing high rate of ASE is amplified through a laser amplifier 7.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial Application Field) The present invention relates to a laser amplification system that uses a laser device using metal vapor or gas as a laser medium as a laser amplifier.

(Prior Art) Laser amplification systems are applied to fields such as energy development, laser processing, and semiconductor manufacturing using lasers, and in recent years, in particular, have been applied to uranium enrichment technology.

The oscillation tube of a laser device using metal vapor or gas as a laser medium has a long longitudinal dimension compared to its diameter. In addition, in order to increase the laser output, multiple laser devices are used, one of which is used as a laser oscillator and the others are used as laser amplifiers, resulting in a laser amplification system that obtains a high laser output as a whole. Often configured. Such a laser amplification system has a configuration as shown in FIG. 7, and a conventional example will be explained with reference to FIG.

The laser oscillator indicated by the reference numeral 1 consists of a laser oscillation tube 2, a driving power source 3 for driving the oscillation tube 2, and a laser oscillation medium supply and exhaust device I4. A master beam 5 emitted from this laser oscillator 1 passes through a reflection mirror 6.6 and enters a first laser amplifier 7. This first laser amplifier 7 has the same configuration as the laser oscillator 1, and has a laser oscillation tube 2. It consists of a driving power source 3 and a laser oscillation medium supply and exhaust device 4.

The amplified beam 8 emitted from this laser amplifier 7 passes through a reflection mirror 6.6 and enters a second laser amplifier 7a. The configuration of this second laser amplifier 7a is the same as that of the first laser amplifier 7a.
This is similar to the laser amplifier 7 of . In this way, the conventional laser amplification system includes a laser oscillator 1, a first laser amplifier 7 and a second laser amplifier 7a in the subsequent stage, and optionally a third laser amplifier (not shown). A large laser amplification beam is obtained by arranging a plurality of laser amplifiers such as the fourth laser amplifier. Further, even when the number of first and second laser amplifiers 7.7a is more than two, the arrangement described above is repeated.

(Problem to be Solved by the Invention) When extracting the master beam 5, that is, the reference laser beam, from the laser oscillation tube 2, a reflecting mirror 6.
6 can be used to align the optical axes. However, as shown in FIGS. 8 and 9, in addition to the high quality beam 9 emitted from the laser oscillator tube 2, 1=AsE10 (
^mplilied 5pon+@neous Emi
Spontaneous emission light (hereinafter referred to as ASE) called ASE is mixed into the transmission beam. This ASEIO causes a loss of amplification energy in the laser amplifiers 7, 7a...
It has the detrimental property of reducing the proportion of high quality beams 9 in the transmitted beam.

Therefore, in the conventional laser amplification system shown in FIG. 7, it is difficult to suppress the loss of amplification energy in the laser amplifiers 7, 7a, etc. and obtain a laser amplified beam with a large proportion of high-quality beam 9. be.

The present invention was made to solve the above problems, and A
It is an object of the present invention to provide a laser amplification system capable of suppressing the loss of amplification energy due to SE and obtaining a highly efficient and high quality laser amplified beam.

[Structure of the Invention (Means for Solving the Problems) The present invention provides a laser amplification system comprising a laser oscillator and at least one laser amplifier in combination with the laser oscillator, wherein a crotch between the laser oscillator and the laser amplifier, Furthermore, the present invention is characterized in that a spatial filter device having a pinhole is provided between the stages of the laser amplifier and other laser amplifiers, if necessary.

The spatial filter device consists of a combination of convex lenses with a pinhole plate having a pinhole interposed between them, or a combination of concave mirrors with the pinhole plate interposed between two concave mirrors. ing.

(Function) ASE from each laser oscillation tube is generated in the laser beam, so when a laser beam containing this ASE is converged with a lens, etc., the high quality beam has high convergence and is extremely Can be narrowed down to a small spot diameter. In contrast, ASE has extremely low convergence. Therefore, a pinhole is placed at the convergence point (focal point) of the high-quality beam, and ASE is removed by this pinhole.
Only a high-quality beam passes through the pinhole and is returned to a parallel beam by a symmetrically arranged convex lens or concave mirror. This pinhole can reduce the loss of amplification energy in a laser amplifier with a high proportion of ASE mixed in. Further, it is possible to eliminate changes in the beam trajectory due to the oscillation wavelength of the laser oscillator being handled.

(Embodiment) An embodiment of the laser amplification system according to the present invention will be described with reference to FIGS. 1 and 2.

In FIG. 1, reference numeral 1 denotes a laser oscillator, and this laser oscillator 1 consists of a laser oscillation tube 2, a driving power source 3 for driving this oscillation tube 2, and a laser oscillation medium supply and exhaust device 4. On the optical axis of the master beam 5 emitted from the laser oscillation tube 2, there is a pair of convex lenses 11 as an intermediate filter device. lla is arranged, and this convex lens 11. Pinhole 12 between lla
A pinhole plate 13 having a central portion thereof is arranged.

A pair of reflective mirrors 6.degree. 6a are arranged behind the convex lens lla. The laser oscillation tube 2 of the first laser amplifier 7 is arranged on the optical axis of the reflection mirror 6a.

This first laser amplifier 7 has the same configuration as the laser oscillator 1, and has a laser oscillation tube 2. It consists of a driving power source 3 and a laser oscillation medium supply and exhaust device 4.

On the optical axis of the amplified beam 8 emitted from the oscillation tube 2 of the first laser amplifier 7, there is a pair of convex lenses II, I as an intermediate filter device, similar to the laser oscillator 1.
A pinhole plate 13 having a pinhole 12 is arranged between the convex lenses If and Ila. A pair of reflective mirrors 6.6a are arranged behind the convex lens lla. A second laser amplifier 7a having the same configuration as the first laser amplifier 7 described above is arranged behind the reflection mirror 6a. In this way, the laser amplification system shown in FIG. A pair of convex lenses 11 provided for the purpose of removing ASE. lla and a pinhole plate 13 having a pinhole 12, and a reflection mirror 6.6a for light adjustment. Thus, the ASE 10 included in the master beam from the laser oscillator 1 is formed by a pair of convex lenses 11. lla and a pinhole plate 13 having pinholes 12, the beam is removed to form a high quality beam 9 which is transmitted to the subsequent laser amplifier 7 shown in the drawing. Through this transmission, the loss of amplification energy due to A S E l (l) can be reduced, and a high-quality amplified beam 8 can be obtained efficiently. In addition, the reference numeral 14 in FIG. 2 indicates the focus of the high-quality beam. , it is necessary that the pinhole 12 of the pinhole plate 13 coincides with its focal point 14.

In addition, in a system in which the number of stages of laser amplifiers 7 is one or more, a convex lens II is also provided between the stages of each laser amplifier 7.
lla and pinhole plate 13 can be placed to remove ASE. Further, in the amplified beams at lower stages where the intensity of the amplified beam 8 has not been sufficiently increased, the content of ASE is high, which is advantageous for improving efficiency.

In the above embodiment, the intermediate filter device includes a pair of convex lenses I1
．． Although the combination of lla and pinhole plate 13 has been described, the combination is not limited to this. For example, as shown in FIG. 3, when the laser beam to be handled is a laser beam 15 containing a plurality of oscillation wavelength components, the trajectory line of the laser beam is the position of the focal point 14 after passing through the convex lens 11, which is the focal point indicated by the broken line. A shift 16 depending on the wavelength occurs at the position 14a, and the trajectory of the laser beam is separated for each wavelength.

In such a case, as shown in Figures 4 to 6,
It is desirable to configure the intermediate filter device by combining reflecting mirrors such as the parabolic mirror 17 or the convex spherical mirror 18.

Specifically, the intermediate filter device shown in FIG. An example is shown in which a pinhole plate 13 is placed at the focal point. In this example, the parabolic mirror 17.17
It is preferable to use a mirror that does not cause distortion of the laser wavefront even off-axis. The parabolic mirror 17.17a shown in FIG. 4 is difficult to manufacture with high precision and tends to be expensive. Therefore, by applying the intermediate filter device as shown in FIGS. 5 and 6, it is easy to manufacture and can be obtained at low cost.

That is, FIG. 5 shows an ordinary concave spherical mirror 18° 18a.
A pair of scraper mirrors 19. which face vertically and have a hole 23 in the center. 19a, and a pinhole plate 13 is arranged between the concave spherical mirrors 18 and 18a. In this example, the interaction between the concave spherical mirror 18.18a, the scraper mirror 19.19a, and the pinhole of the pinhole plate 13 produces a high-quality output beam 20 with ASE removed from the laser beam 15 containing a plurality of oscillation wavelength components. It can be radiated.

The example of FIG. 6 is a modification of FIG. 5, and shows an example in which a double-sided coated scraper mirror 21 having a hole 23 is arranged between concave spherical mirrors I11.18a. In this example as well, the laser beam 15 containing a plurality of oscillation wavelength components enters the surface of the double-sided coating scraper 21, is reflected between the concave spherical mirrors 18 and 18a, and is reflected by the hole 2.
3, ASE is removed and a high quality output beam 22 with ASE removed from the back side can be obtained.

By arranging the intermediate filter as described above, ASE contained in the master beam 5 and the amplified beam 8 from the laser oscillation tube can be removed.

[Effects of the Invention] According to the present invention, ASE harmful to laser beam amplification is eliminated.
can be removed, thereby amplifying the laser beam with high efficiency and obtaining a high-quality amplified beam. Further, it is possible to eliminate changes in the beam trajectory due to the oscillation wavelength from the laser oscillator.

[Brief explanation of drawings]

FIG. 1 is a system diagram showing an embodiment of the laser amplification system according to the present invention, FIG. 2 is a device layout diagram showing the spatial filter device in FIG. 1, and FIG. 3 is a laser beam of the spatial filter device in FIG. Beam trajectory diagrams, Figures 4 to 6
The figures are device layout diagrams showing other examples of spatial filter devices, Figure 7 is a system diagram showing a conventional laser amplification system, and Figure 8 is the trajectory line of spontaneous emission light mixed into the laser beam in Figure 7. 9 is a longitudinal sectional view of the laser beam of FIG. 8. 1... Laser oscillator 2... Laser oscillation tube 3... Drive power source 4... Laser oscillation medium supply, exhaust device 5... Master beam 6... Reflection mirror 7... Laser amplifier 8... ...Amplified beam 9...High quality beam 10...ASE 11.lla...Convex lens 2...Pinhole 3...Pinhole plate 4...Focus of high quality beam 5...Multiple Laser beam 6 containing the oscillation wavelength component of
... Focus shift due to wavelength 7 ... Parabolic mirror ... Concave spherical mirror 9 ... Scraper mirror 20 ... Outgoing beam 21 ... Double-sided coating scraper mirror 22 ...
...Outgoing beam 23...Kou (8733) Agent: Yoshiaki Inomata, patent attorney (and others)
1 person) $3 Zufutsu 4 Alliance Kayo Zu Mei Otsu Alliance Kayao Zu Sobozu Zuwa Zu

Claims (1)

[Claims] a laser oscillator, and at least one
1. A laser amplification system comprising a combination of two laser amplifiers, characterized in that a spatial filter device having a pinhole is provided between the laser oscillator and the laser amplifier.