JPH1126851A - Laser device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide laser device which can emit a pulse beam having a high average power density, a uniform pulse waveform, and a high repetition rate by providing a delaying optical system which elongates the optical pulse width of a randomly polarized beam which is randomly polarized through a polarizing optical system. SOLUTION: A half mirror 3 and reflecting mirrors 4, 5, and 6 constitute a delaying optical system which elongates the optical pulse width of randomly polarized light randomly polarized through a polarizing optical system. When the optical system is operated, the system synthesizes two laser beams 7 and 8 into one coaxial beam 9 having a high repetition rate by using a polarizing prism 1. The high repetition rate is obtained by shifting the pulse time of the laser beams 7 and 8 from each other. Since the synthesized polarized beam 9 has orthogonally polarized light rays at every pulse, the beam 9 is resynthesized into a randomly polarized beam 10 through a depolarizing plate 2. Thereafter, the beam 10 is split into two beams by means of a half mirror so that one of the two beams may become a delayed beam.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a laser device capable of obtaining laser light having a high power density and a high repetition rate.

[0002]

[Prior art]

(1) In order to obtain a pulse laser beam having a high repetition rate, a technique of synthesizing two pulse laser beams coaxially can be mentioned. In this method, two beams are orthogonalized, and a half mirror (generally, a reflectance of 50%) is provided at an orthogonal position.
Is set at 45 ° and the two laser pulses are shifted in time to obtain a repetition number obtained by adding the pulse repetition numbers of the two beams.

(2) In order to obtain a beam having a high average power density, two beams are provided with orthogonally polarized light in advance, and are coaxially combined using a polarizing prism or the like. (3) As a method of extending the pulse width, the beam is divided into two beams using a half mirror, and one of the divided beams is looped.
And then return to the half mirror to return to the same optical axis.

[0004]

In order to obtain a beam having a high average power density, a wide pulse width and a high repetition rate, first, as in the prior art (2), the beam is preliminarily polarized. , And by creating a high repetition beam with a high average power density by coaxial synthesis using a polarizing prism. However, in order to extend the pulse width, as in the prior art (3), a delay time is created by looping the transmission side beam into two using a half mirror and forming a delay time. A method of making the beam incident from behind the beam on the opposite side of the film. However, since the polarization is combined, polarization is provided for each pulse, and the reflectance of the half mirror for extending the pulse width differs depending on the polarization (P-polarized light has a higher reflectance). Large reflectance). As a result, even if the transmission side beam is looped and returned to the same axis, a difference occurs in the degree of elongation for each pulse.

An object of the present invention is to solve the above-mentioned disadvantages and to provide a laser device capable of obtaining a pulse beam having a high average power density and a high repetition rate with a uniform pulse waveform. With the goal.

[0006]

According to the present invention, there is provided a synthesizing optical system for coaxially synthesizing two laser beams having polarized light,
A polarizing optical system for randomly polarizing the polarizing beam synthesized by the synthesizing optical system, and a delay optical system for extending the light pulse width of the randomly polarized beam randomly polarized by the polarizing optical system are provided. It is a laser device.

[0007]

Embodiments of the present invention will be described below with reference to the drawings. The laser device according to the present invention is configured as shown in FIG. 1, and a polarizing prism 1, a depolarizing plate 2, and a half mirror 3 are arranged on a same line at predetermined intervals. Reflective mirrors 4, 5, and 6 are arranged at predetermined intervals behind the half mirror 3 so as to form a delay loop together with the half mirror 3.

In this case, the polarizing prism 1 constitutes a synthesizing optical system for coaxially synthesizing two laser beams having polarized light, and the depolarizing plate 2 is a polarizing beam synthesized by the synthesizing optical system. A polarization optical system for randomly polarizing the light, and a half mirror-3 and reflection mirrors 4, 5, 6 for extending a light pulse width of a random polarization beam randomly polarized by the polarization optical system. Is composed.

Reference numeral 7 in the drawing denotes a laser beam which is a laser pulse having S-polarized light, and reference numeral 8 denotes a laser beam which is a laser pulse having P-polarized light. 9 is laser beam 7
A high repetition polarization beam obtained by synthesizing the polarization beam 8 and the random beam 10 is a random polarization beam in which the polarization beam 9 is randomly polarized. Furthermore, after passing through a delay loop, the half mirror-3 is used.
Is a laser beam divided in half, and the main, first and second laps are combined as shown in FIG.

In operation, the two laser beams 7 and 8 to be combined have orthogonal polarizations as described above, but the two laser beams 7 and 8 are polarized by a polarizing prism. 1 to form a single high-repetition-rate polarization beam 9 on the same axis. At this time, since the half mirror is not used, it is possible to perform the synthesis without losing the pulse energy. At this time, a high repetition rate is obtained by shifting the pulse times of the laser beams 7 and 8.

Since the synthesized polarization beam 9 has a polarization orthogonal to each pulse, it passes through the depolarizer 2 to form a random polarization beam 10. After that,
The laser beam is divided into two laser beams by the Fumilla-3, one of which is a delay loop. Here, the pulse waveform of the divided laser beam 11 has a constant shape regardless of the pulse.

After the time is delayed by the delay loop and the light passes through the depolarizing plate, it is returned to the half mirror-3 again. Here, one round of the delay loop is made, half of the laser beam returned is returned to the main optical axis, and half of the laser beam makes two rounds of the delay loop. The laser beam that has made two rounds is divided in half by the half mirror 3 like the laser beam that has made one round, and is divided into energy to be synthesized and energy to return to the delay loop. Hereinafter, similarly, the light is returned to the main optical axis with a time delay.

An optical element for imparting polarized light to the laser beam may be provided in front of the combining optical system. A down collimating optical system for reducing the beam diameter may be provided in front of the depolarizing plate 2 constituting the polarizing optical system. Further, a depolarizing plate may be newly provided in the delay optical system.

[0014]

According to the present invention, a laser device comprises a synthetic optical system for coaxially synthesizing two laser beams having polarized light, and a polarized beam synthesized by the synthetic optical system. Since the optical system comprises a polarizing optical system that randomly polarizes the light, and a delay optical system that extends the light pulse width of the randomly polarized beam that is randomly polarized by the polarizing optical system, the laser beam obtained is obtained.
The pulse waveform has a constant shape, and can be synthesized with little loss of the energy of the original laser beam, and further high repetition can be achieved.

[Brief description of the drawings]

FIG. 1 is a configuration diagram showing a laser device according to an embodiment of the present invention.

FIG. 2 is an enlarged waveform diagram showing a part of FIG. 1;

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Polarizing prism (synthetic optical system), 2 ... Depolarizing plate (polarizing optical system), 3 ... Half mirror, 4, 5, 6 ... Reflecting mirror (delay optical system), 7, 8 ... Laser -Mu.

Claims (4)

[Claims] 1. A synthetic optical system for coaxially synthesizing two laser beams having polarized light, a polarizing optical system for randomly polarizing a polarized beam synthesized by the synthetic optical system, and A delay optical system for extending an optical pulse width of a random polarization beam that has been randomly polarized by a polarization optical system. 2. The laser device according to claim 1, further comprising an optical element for imparting polarized light to said laser beam, before said synthetic optical system. 3. A down collimator for reducing a beam diameter before a first depolarizing plate constituting the polarizing optical system.
2. The laser device according to claim 1, further comprising a scanning optical system. 4. The laser device according to claim 1, wherein a second depolarizing plate is provided in the delay optical system.