JPH04241484A - Laser light generator - Google Patents

Abstract

PURPOSE:To generate laser light with much energy concentrated in a narrow divergence angle. CONSTITUTION:Pumping laser light output from a plurality of laser diodes 1a to 1d is applied to different positions of a laser medium 6. Thus heat lenses 6a to 6d are formed in the laser medium 6. Four laser light beams generated from the laser medium 6 are input to a non-linear optical crystal element, 9. Second harmonics of the same phase are generated from the nonlinear optical crystal element 9.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a laser beam generator capable of generating a laser beam with a large amount of energy concentrated in a narrow divergence angle range.

0002

2. Description of the Related Art The present applicant proposed a very compact phase-locked solid-state laser in Japanese Patent Laid-Open No. 2-198441. In this proposal, a plurality of pumping laser beams generated by a plurality of laser diodes are irradiated onto different positions of a laser medium. Then, a thermal lens is generated in this laser medium, and a plurality of laser resonators are substantially constituted by this thermal lens, the laser medium, and mirrors arranged before and after the laser medium. As a result, a plurality of laser beams are generated from the laser medium.

0003

[Problems to be Solved by the Invention] However, as a result of experiments, it has been confirmed that in the laser light generating device proposed above, adjacent oscillation regions of the laser medium tend to oscillate in opposite phases to each other. As a result, for example, when two oscillation regions are irradiated with pumping light to generate two laser beams, the far-field pattern becomes bimodal as shown in FIG. 5. As a result, it has not been possible to generate laser light with stronger energy concentrated in a narrow range.

The present invention has been made in view of the above situation, and it is an object of the present invention to make it possible to generate a laser beam with strong energy concentrated in a narrow divergence angle.

[0005]

[Means for Solving the Problems] A laser beam generating device of the present invention includes a pumping light source that generates at least two pumping lights, and a part that receives irradiation with the pumping light generated by the pumping light source. , a laser medium that forms a thermal lens and generates laser light, and a laser medium that is provided before and after the laser medium, reflects at least a part of the laser beam output from the laser medium, and resonates with the laser medium in which the thermal lens is formed. It is characterized by comprising a mirror forming a cavity, and a nonlinear optical crystal element that generates second harmonics of at least two laser beams output from the resonator.

[0006]

[Operation] In the laser beam generator having the above configuration, the plurality of laser beams generated by the plurality of pumping lights are
The light is incident on a nonlinear optical crystal element, and a second harmonic is generated. As a result, it becomes possible to obtain an in-phase beam, that is, a unimodal far-field image.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a diagram showing the configuration of an embodiment of a laser beam generator according to the present invention. The pumping light source 1 is composed of laser diodes 1a to 1d. Pumping laser beams generated by laser diodes 1a to 1d are transmitted to coupler 3 via optical fibers 2a to 2d. The coupler 3, as shown in FIG.
In this embodiment, the optical fibers 2a to 2d are arranged at four vertices of a square. The four laser beams output from the coupler 3 are converged by a lens 4 and irradiated to different positions of a laser medium 6 via a mirror 5. As a result, inside the laser medium 6 (Nd:YAG),
In response to the irradiation of the four laser beams, the irradiated portions are heated to form four thermal lenses 6a to 6d. As a result, four resonant parts are substantially formed inside the resonator 10 corresponding to the mirrors 5 and 7 and the four thermal lenses 6a to 6d arranged before and after the laser medium 6. .

That is, in the region irradiated with one pumping laser beam, one fundamental mode oscillation laser beam is generated, and this laser beam is reflected by the mirror 7 and is transmitted to the mirror 5 via the thermal lens 6a. irradiated. Then, the laser beam reflected by the mirror 5 is again irradiated onto the mirror 7 via the thermal lens 6a. In this way, the laser beam reciprocates between the mirrors 5 and 7, and a laser beam with strong energy is generated. Note that at this time, the thermal lens 6a
and mirror 7 substantially form a concave mirror.

Similar operations are performed in the other three areas. As a result, four powerful laser beams are generated.

[0010] The mirror 5 receives one laser beam for pumping.
00% transmission and the laser beam generated in the laser medium 6 is
It is formed to be 00% reflective. Also, mirror 7
is several percent to 10% of the laser light generated in the laser medium 6.
It allows a few percent of the light to pass through and reflects the rest.

The four laser beams output from the mirror 7 are incident on a nonlinear optical crystal element 9 via a lens 8 inserted as required. As described above, the far-field pattern of the two laser beams output from the mirror 7 is bimodal. That is, for example, when focusing on two laser beams arranged in the vertical direction, a far-field image in a plane including the y-axis (in a vertical plane) is as shown in FIG. In addition, even when focusing on the two laser beams arranged horizontally in the figure, within the plane including the x-axis (
The far-field image in the horizontal plane) is also bimodal as shown in FIG.

Therefore, in the present invention, as shown in FIG.
The light is incident on a nonlinear optical crystal element 9 made of a uniaxial crystal (having a uniaxial crystal) or the like. The nonlinear optical crystal element 9 generates a second harmonic of the incident laser light. As mentioned above, resonator 1
The laser beams La and Lb arranged in the vertical plane, which are incident on the nonlinear optical crystal element 9 from zero, have opposite phases (the same applies to the laser beams Lc and Ld arranged in the horizontal plane). As a result, the far-field patterns of the two light-emitting regions become bimodal, as shown in FIG. Expressing this in a formula is as follows. exp(−(πψω0/λ)2)・sin(πψd/λ
)

[0013] Here, ψ, ω0, and d each represent the following meanings. ψ: Divergence angle ω0: Size of light beam of light emitting area d: Distance between two light emitting areas

As is clear from the above equation, the value of the above equation is ψ
= 0, it becomes 0.

On the other hand, the second harmonic component emitted from the nonlinear optical crystal element 9 has the same phase as is clear from the following equation. sin2(θ+π)=(-sinθ)2=sin2θ

[
As a result, two laser beams La and Lb (Lc
and Ld) interfere, and a unimodal far-field image as shown in FIG. 4 is obtained. This is expressed by the following formula. exp(−(πψω0/λ)2)・cos(πψd/λ
)

It is clear that the above equation has a maximum value when ψ=0.

The characteristic shown by the broken line in FIG. 4 shows the case of a single laser or an array that emits light incoherently, which has a light emitting region with the same size of light intensity included in a unit divergence angle. As is clear from comparing the case of the present application shown by the solid line and the case of this broken line, it can be seen that the laser beam of the present application has stronger energy concentrated in a narrower range.

Of course, if it is desired to obtain unimodal characteristics only in the horizontal plane or in the vertical plane, it is obvious that the laser diode 1 only needs to be provided in either the vertical plane or the horizontal plane. It is.

[0020]

Effects of the Invention As described above, according to the laser beam generator of the present invention, the second
Since the harmonics are generated by a nonlinear optical crystal element and the laser beam is in the same phase, it is possible to generate a laser beam with a large amount of energy concentrated in a narrow divergence angle.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the configuration of an embodiment of a laser beam generator of the present invention.

FIG. 2 is a front view of the coupler in FIG. 1.

3 is a diagram illustrating the positional relationship of laser beams incident on the nonlinear optical crystal element in FIG. 1. FIG.

4 is a diagram illustrating a far-field image in the embodiment of FIG. 1. FIG.

FIG. 5 is a diagram illustrating a far-field image of an example of a conventional laser beam generation device.

[Explanation of symbols]

1 Laser diode 2 Optical fiber 3 Coupler 4 Lens 5,7 Mirror 6 Laser medium 6a to 6d thermal lens 9 Nonlinear optical crystal element 10 Resonator

Claims (1)

[Claims] 1. A pumping light source that generates at least two pumping lights, and a part of which is irradiated with the pumping light generated by the pumping light source to form a thermal lens and generate laser light. a laser medium, a mirror provided before and after the laser medium, which reflects at least a portion of the laser light output from the laser medium and forms a resonator together with the laser medium in which the thermal lens is formed; 1. A laser beam generator comprising: a nonlinear optical crystal element that generates second harmonics of at least two laser beams output from a resonator.