JPS63253686A - Pulse laser device - Google Patents

Abstract

PURPOSE:To forward laser beams having high quality and a large output by synchronizing pulse laser beams by first excitation oscillation with second excitation oscillation, feeding back and injecting pulse laser beams to a laser oscillator and conducting second excitation by self-injection locking. CONSTITUTION:First laser beams polarized to the feedback side by a polarization beam splitter 5 are reflected by a turning mirror 9, the plane of polarization of laser beams are further turned at 90 deg. by a Faraday rotor 4b, and laser beams are returned to the original plane of polarization. Laser beams from the Faraday rotor 4b are controlled so that a beam diffusion angle is minimized in a spatial filter 6. A wavelength is selected by selecting and transmitting only a specified wavelength range in a wavelength selective element 7, and laser beams are injected into a laser chamber 1 from a small hole at the center of a concave mirror 2a constituting an unstable resonator from the turning mirror 9c. Accordingly, fed-back and injected laser beams having high quality are used as species, and second laser oscillation having a high output and high quality in the same extent as fed-back and injected laser beams is conducted.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a pulse laser device that oscillates a high-quality laser beam with relatively high output.

(Prior art) Conventionally, a pulsed laser MU using a gas laser, solid state laser, or liquid laser has a relatively high output of a high quality laser beam whose spectral width and divergence angle are controlled very well. For example, a device not shown in FIG. 6 is known for causing oscillation.

In FIG. 6, 11 is a master oscillator, which has a wavelength selection element 7 such as a prism in the resonator and 7 perchers that control the transverse mode, and depending on the excitation oscillation of the laser chamber 1, the output is small, but the spectral width and divergence A pulsed laser beam whose angle is very well controlled is output to the slave oscillator 12 via the folding mirror 9.

The slave oscillator 12 excites and oscillates the laser output from the master oscillator 11 by injecting the laser output from the master oscillator 11 into the laser chimebar 1 through the aperture of the concave reflector 2a of the concave reflector 2a and convex reflector v12b constituting the unstable resonator. The quality beam is transmitted to the outside from the convex reflecting mirror 2b side forming the unstable resonator as a relatively large laser output 8.

(Problems to be Solved by the Invention) However, in such a conventional pulse laser device, two laser oscillators are required to obtain high quality and relatively high output laser light. There are problems in that the device configuration is complicated and large, and the cost is also high.

(Means for Solving the Problems) The present invention was made in view of these conventional problems, and it is possible to produce high-quality and relatively high-output laser light by using only one laser oscillator. The purpose of the present invention is to provide a pulsed laser device that can excavate.

In order to achieve this object, the present invention includes: one laser oscillator that generates pulses of laser light; excitation means that causes the laser oscillator to emit pulses at least twice in succession;
an optical path switching means for switching so that the first laser beam pulsed from the laser oscillator is sent out to the return side and the laser beam pulsed a second time is sent out to the output side; A return optical path is provided for synchronously injecting laser light into the pulse excavator in synchronization with the second pulse excavation.

(Function) In the present invention configured as described above, one laser oscillator is made to oscillate pulses continuously at least twice, and the first
The pulsed laser beam from the first excitation oscillation is synchronized with the second excitation oscillation and is feedback-injected into the laser oscillator, and the second excitation excavation by so-called self-injection synchronization generates a laser beam with a high intensity of 71 and a large output. Can be sent externally.

(Example) FIG. 1 is an explanatory diagram showing one embodiment of the present invention.

First, to explain the configuration, 1 is a laser chamber,
An unstable resonator consisting of a concave mirror 2a and a convex mirror 2b is provided before and after the laser chamber 1 (thereby forming a laser oscillator). For example, an excimer laser device having the structure shown in FIG. 3 is used as the laser chamber 1, and the excitation circuit 15 of this excimer laser device is as shown in FIG.

In the excitation circuit shown in Figure 2, HV is a high voltage power supply, SG is a spark gap, C1 is a DC cut capacitor, and L
C is a laser chamber, C3 is a storage capacitor, CI)1. Ca2 is the peaking capacitor, L1
~L3 is the inductance caused by the wiring.

In the excimer laser device shown in FIG. 3, a pair of discharge electrodes for laser excitation is constituted by a discharge electrode 20 and a discharge electrode 24 made of a thin metal plate or mesh that is not destroyed by arc discharge and transmits X-rays, A uniform and uniform electric field distribution is formed between the discharge electrodes. Further, the discharge N-pole 20 includes a plurality of peaking capacitors Cpl, Ca
2 is installed. Furthermore, the electron gun 21 and the small metal foil 30 form an X-ray generating section, and the X-ray generating section is
X-rays are supplied to preliminarily ionize the laser gas 22 within the laser titanium bar. The laser beam is emitted perpendicularly to the plane of the paper. Further, the chamber in which the main discharge electrode 20 is installed is filled with laser gas 22, while the chamber in which the electron gun 21 is installed is drawn to a predetermined vacuum state by a vacuum pump.

The left side of the laser chamber in which the main discharge electrode 20 is installed is filled with insulating oil 23, and in the insulating oil 23 there are circuits such as storage capacitor 〇s1 spark gap SG and capacitor 01 in the excitation circuit shown in Fig. 2. elements are incorporated.

In this way, the excimer laser device shown in FIG. 3 with which the excitation circuit shown in FIG. An X-ray generating section that provides a radiation distribution, and a peaking capacitor Cp1. By adopting CD2, it is possible to perform an excited discharge capable of laser oscillation even at the second linking peak of the main discharge current. Therefore, when excited oscillation is performed by an external trigger, the laser chamber is activated twice in a row. Laser light can be pulsed.

Referring again to FIG. 1, the laser chamber 1 has a polarizing filter, a polarizing beam splitter, and a polarizing beam splitter on the laser beam output side.
A polarizing element 3 such as a Glan-Thompson prism, a Faraday rotator 4a, and a polarizing beam splitter 5 are sequentially installed.
These constitute an optical path switching means for switching the pulsed laser light from the laser chamber 1 to be sent out to the return side or to the output side.

That is, the polarizing element 3 linearly polarizes the laser light pulsed by the excitation discharge of the laser chamber 1, and the Faraday rotator 4a receives a driving current from the constant current source 27 when the switch 26 is turned on by the controller 25. is the polarization plane of the laser beam linearly polarized by the polarizing filter 3.
When the laser beam is rotated by 0° and the current supply is cut off by turning off the switch 26, the laser beam polarized by the polarizing filter 3 is allowed to pass through without being rotated in the plane of polarization. Further, the polarizing beam sinter 5 polarizes the laser beam whose polarization plane has been rotated by 90 degrees by the Faraday rotator 4a to the return side that orthogonally covers the laser beam, and polarizes the beam light whose optical plane has not been rotated by 90 degrees by the Faraday rotator 4a. is sent out as is as laser output 8.

The laser beam polarized to the return side by the polarizing beam splitter 5 is composed of a folding mirror 9a, a Fut-Lab rotator 4b, a spatial filter 6 composed of lenses and a pinhole, a folding mirror 9b, an etalon, a grading, and a prism shade. A concave surface vL2 forming an unstable resonator via a return optical path including a wavelength selection element 7 and a folding mirror 9C 1411
The laser beam is injected back into the laser chamber 1 through the small hole in the center of a. .

A Hun-Love rotator 4b installed in the return optical path returning from the polarizing beam splitter 5 to the laser beam non-performer 1 rotates the laser beam, which has been rotated 90' by the Faraday rotator 4a, further by 90'. to return to the original polarization plane.

Further, the spatial filter 6 provided subsequent to the Faraday rotator 4b functions as a diffusion angle control means for reducing the beam diffusion angle of the laser beam.

Further, a wavelength selection element 7 provided subsequent to the spatial filter 6 selectively passes only a specific laser oscillation wavelength. In this way, the laser light that is returned and injected into the laser chamber 1 by the spatial filter 6 and wavelength selection element 7 provided in the return optical path is only high-quality laser light with a small diffusion angle and a wavelength spectrum concentrated at a specific wavelength. It becomes selected and feedback-injected.

Next, the operation of the embodiment shown in FIG. 1 will be explained.

The controller 25 outputs a trigger signal to the excitation circuit 15 at a predetermined laser oscillation timing.
The excitation circuit 15 generates an excitation discharge pulse in the laser chamber 1 in response to a trigger signal from the excitation circuit 15, so that a discharge current as shown in FIG. 4(a) flows through the laser chamber 1 from the excitation circuit 15.

In the discharge current shown in FIG. 4(a), the first excitation oscillation of the laser beam is performed at the first ringing peak P1, and the excitation lJI! that allows laser oscillation also occurs at the second ringing peak P2! The electric state is obtained, and the second laser oscillation is performed at the second ringing peak P2. Here, the first ringing peak P1 and the second ringing peak P1
The time interval Δt of the ringing peak P2 is a constant delay time depending on the excitation circuit shown in FIG. The laser beam emitted from the laser chamber 1 by the first laser oscillation is converted into linearly polarized light by the polarizing filter 3. 1tlJ Shita Controller 2
Since the drive current is supplied from the constant current source 27 when the switch 26 is turned on by the switch 5, the polarization plane of the laser beam linearly polarized by the polarizing element 3 is rotated by 90' and the polarized beam enters the polarizing beam 1 liter 5 by q dimension. do. The polarizing beam splitter b, into which the Rayleigh light whose polarization plane has been rotated by 90' is incident, polarizes the incident Rayleigh light on the feedback side (orthogonal to the laser output 8).

The laser beam polarized to the return side by the polarizing beam splitter 5 is reflected by the return mirror 9, and is then passed through the Faraday rotator 4b.
At this time, since the switch 26 is turned on and the drive current is being supplied by the constant current source 27, the plane of polarization of the laser beam from the folding mirror 9 is further rotated by 90', and the plane of polarization is rotated by the Faraday rotator 4a. Returns light to its original polarization plane.

The laser beam from the Faraday rotator 4b is filtered through a spatial filter 6
The wavelength is selected by selectively transmitting only a predetermined wavelength band in the wavelength selection element 7, and the small central part of the concave surface vL2a constituting the unstable resonator is It is injected into the Rede chamber 1 through the hole.

The time from the first laser oscillation by the laser chamber 1 until the laser beam is returned and injected via the return optical path is set to match the delay time Δt until the second ringing peak P2 shown in FIG. The optical path length is adjusted,
Therefore, the feedback laser beam from the first laser oscillation is injected into the laser chamber 1.
is in an excited discharge state due to the second ringing peak P2 of the discharge current caused by the excitation circuit 15, and therefore the second
The excited discharge and the feedback injection of laser light can be synchronized, and the high-quality feedback-injected laser light becomes a seed that produces a high-quality and high-output laser beam with the same level of quality and output as the feedback-injected laser light. The second laser oscillation is performed.

In the second laser oscillation synchronized with this feedback injection of laser light, the controller 25 turns off the switch 26 to cut off the supply of drive current from the constant current source 27 to the Faraday rotator 4a. The laser beam oscillated from the Sea 1 Azimber 1 during the second Sea 1 A firing is incident on the polarizing beam splitter 5 without undergoing rotation of the plane of polarization by the Fut-Lab rotator 4a. The laser light generated by the oscillation is a polarized beam snoritzer.
5 and is sent out as a laser output 8 to the outside.

Figure 5 shows the wavelength spectrum distribution of the first laser beam and the second laser beam emitted from the laser chamber 1 in Figure 1. The wavelength spectrum has a wide spread and the power level is low, but by controlling the wavelength selection and diffusion angle and synchronously injecting the laser light from the first oscillation through the feedback optical path, the second feedback The second laser beam obtained by excitation oscillation synchronized with the injection has a wavelength spectrum concentrated on a specific wavelength and is a high-power laser emission output.

In addition, although the above embodiment took an excimer laser device as an example, the present invention is not limited to this, and may be applied to a gas laser,
Even if it is a solid state laser or a liquid laser, it can be applied as is as long as it is a device that can oscillate pulses at least twice in succession at °C.

In addition, in the embodiment shown in FIG. 1, the laser chamber 1
The laser beam from the resonator is converted into linearly polarized light by the polarizing element 3 outside the resonator, but instead of providing the polarizing element 3 outside the resonator, the window of the laser chamber 1 is set at the Brewster angle, etc. A polarizing element may be provided inside.

(Effects of the Invention) As explained above, according to the present invention, only one excimer laser device (for example, using a laser chamber equipped with a main discharge electrode and an [pre-ionization X-ray generation section]) can be used. It is possible to oscillate high-quality laser light with a wavelength spectrum concentrated at a specific wavelength and a small diffusion angle at a relatively high output, and the device configuration is significantly simplified compared to the case where two conventional laser oscillators are used. It can be miniaturized, and the cost can be reduced.

Furthermore, since the timing of synchronous oscillation due to feedback injection of laser light can be accurately determined by the optical path length of the feedback optical path, synchronous jitter hardly occurs in synchronous oscillation due to feedback injection of laser light.

[Brief explanation of the drawing]

Fig. 1 is an explanatory diagram showing an embodiment of the present invention, Fig. 2 is a circuit diagram showing an example of the excitation circuit shown in Fig. 1, and Fig. 3 is an excimer laser which is an example of the laser chamber shown in Fig. 1. An explanatory diagram of the MA construction of the device, Fig. 4 is a time chart showing the excavation discharge current for excitation of the laser chamber and the laser output waveform, and Fig. 5 is the wavelength of the first and second laser output according to the present invention. FIG. 6, a diagram showing a spectrum, is an explanatory diagram showing a conventional example. 1 Elm-γ chamber 2a, 2b: unstable resonator 3: lIa optical filter 4a, 4b: horn llab-rotator 5: polarizing beam splitter 6: spatial filter 7: wavelength selection elements 9a to 9C: folding mirror 15 : Excitation circuit 20: Main discharge electrode 21: Auxiliary discharge electrode 22: Laser gas 23: Insulating oil 25: Controller 26: Switch 27: Constant current source

Claims (2)

[Claims] (1) A laser oscillator that pulses a laser beam; Excitation means that causes the laser oscillator to pulse at least twice; and a second pulse that sends out the first laser beam pulsed from the laser oscillator to the return side. an optical path switching means for switching the pulsed laser beam to the output side; and synchronously injecting the pulsed laser beam sent to the feedback side by the optical path switching means into the pulse oscillator in synchronization with the second pulse oscillation. A pulsed laser device comprising: a return optical path; (2) The feedback optical path includes wavelength selection means for selectively transmitting a specific wavelength of the feedback laser beam, and diffusion angle control means for controlling the diffusion angle of the laser beam to an optimum state. The pulse laser device according to scope 1.