JP2001068768A - Light excited solid-state laser oscillator - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a light excited solid-state laser oscillator which is capable of outputting a high power by a method wherein resonator systems are connected in series. SOLUTION: A light excited soid-state laser oscillator 1 is equipped with a semiconductor laser 9 which functions as an excitation light source to excite a laser medium 3. One of optical elements 13 which concentrate the exciting laser rays 11 emitted from the excitation light source 9 on the laser medium 3 is provided above the laser medium 3, and two of the optical elements 13 are provided below the laser medium 3, that is, a closed exciting optical system is composed of the exciting light source 9 and the three optical elements, and optical elements which are each provided in an upper space above the laser medium 3 and a lower space below the laser medium 3 to form an optical resonator 25 which is provided with an optical axis 27 that extends nearly vertical to the laser medium 3.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an optically pumped solid-state laser oscillator. More specifically, the present invention relates to an optically pumped solid-state laser oscillator that can easily obtain high output by connecting a plurality of solid-state laser oscillators.

[0002]

2. Description of the Related Art FIG. 4 shows a diagram of Applied Physics B58, 365-372.
(1994) shows an outline of an optically pumped solid-state laser oscillator.

As shown in FIG. 4, a laser medium (Yb: Y
AG) 41 is disposed on a coolable metal heat sink 42. The back surface of the laser medium 41 is coated with a reflective film (not shown) that totally reflects the excitation light 44 described later.

An emission end 43 of an optical fiber for emitting laser light is provided obliquely above the laser medium 41 on the left side. Further, a condenser lens 45 for condensing the excitation light 44 emitted therefrom on the reflection film of the laser medium 41 at an incident angle i is provided.

The excitation light 44 incident on the laser medium 41 is partially absorbed when exciting the laser medium 41, and the unabsorbed excitation light 44 is reflected by the above-mentioned reflection film at a reflection angle r (r = r = r).
The light is reflected at i), and at this time, a part is again absorbed by the laser medium 41.

The remaining excitation light 44 not absorbed at this stage passes through a condenser lens 46 provided diagonally above and to the right of the laser medium 41, becomes almost parallel, is reflected by a plane mirror 47 provided behind, and travels outward. To reverse the laser medium 41 again.
It is provided so as to be incident on.

[0007] As a result, the excitation light 44 passes through the laser medium 41 twice, during which the excitation is performed four times in total.

The back surface of the laser medium 41 is also provided with a coating that totally reflects the oscillation light 48, and a total reflection mirror 4 arranged above the front side of the laser medium 41.
The laser is oscillated by an optical resonator having a V-shaped optical path composed of the output mirror 9 and the output mirror 51.

[0009]

As described above, the conventional optically pumped solid-state laser oscillator has a problem in that it is impossible to increase the output by series coupling of the resonator system in the V-shaped optical path resonator structure.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and an object of the present invention is to provide an optically pumped solid-state laser oscillator capable of increasing the output by series coupling of a resonator system. is there.

[0011]

According to a first aspect of the present invention, there is provided an optically-pumped solid-state laser oscillator comprising a semiconductor laser as an excitation light source for exciting a laser medium. One optical element for condensing the excitation light from the laser medium into the laser medium is provided in the upper space on the front side of the laser medium and two in the lower space on the rear side, and a total of three optical elements above and below the laser medium and the excitation light source are provided. The gist of the present invention is to provide an excitation optical system which is closed by, and to provide an optical element constituting an optical resonator having an optical axis substantially perpendicular to the laser medium in the upper space on the front side and the lower space on the back side of the laser medium. Things.

According to a second aspect of the present invention, there is provided an optically-pumped solid-state laser oscillator according to the first aspect, wherein the laser medium is formed in a plate shape, and the pumping light source for exciting the laser medium is provided. The gist is that a plurality of sets of excitation optical systems are provided.

According to a third aspect of the present invention, there is provided an optically-pumped solid-state laser oscillator according to the first or second aspect, wherein the laser medium is provided on a transparent thermally conductive substrate. The gist of the present invention is to support the heat sink.

According to a fourth aspect of the present invention, there is provided an optically-pumped solid-state laser oscillator according to any one of the first to third aspects, wherein a plurality of laser media are provided on the optical axis of the optical resonator at a distance. The gist is that the excitation light source for exciting the plurality of laser media and the excitation optical system are separately provided.

[0015]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is an explanatory view of a first embodiment of an optically pumped solid-state laser oscillator according to the present invention. The optically pumped solid-state laser oscillator 1 includes a laser medium, an excitation unit for exciting the laser medium, an optical resonator, and the like.

The laser medium 3 is, for example, Yb: YAG (Ytt
It has a plate-like shape, and has a coating that is non-reflective to the wavelength of the excitation light on both the front and back surfaces. Further, the laser medium 3 is a plate-shaped heat conductive substrate 5 made of, for example, sapphire or diamond, which is transparent to the wavelength of laser light and excitation light generated by laser oscillation and has high heat conductivity.
Optically adhered on Further, the heat conductive substrate 5 is supported on its circumference by a metal heat sink 7 which can be cooled.

An excitation semiconductor laser 9 is provided obliquely above the left side of the laser medium 3, and an excitation laser beam 11 a emitted from the semiconductor laser 9 is supplied to the laser medium 3.
A condensing lens 13 is provided as an optical element for condensing and irradiating a substantially central portion O in the thickness direction of the device.

An optical element that receives the laser light 11b that has passed through the laser medium 3 and the heat conductive substrate 5 and has become divergent light, and reflects it as a substantially parallel laser light 11c in a direction orthogonal to the heat sink 7. A first spherical mirror 15 is provided diagonally below and to the right of the laser medium 3. Laser medium 3
A second spherical mirror 17 as an optical element that receives the laser beam 11c from the first spherical mirror 15 and converges and irradiates the central part O of the laser medium 3 diagonally above and to the right of and above the first spherical mirror 15. It is provided.

The heat sink 7 located between the first spherical mirror 15 and the second spherical mirror 17 has a parallel ray 11c.
There is provided an opening 19 through which the air can pass.

On the lower left side of the laser medium 3,
The laser beam 11d from the second spherical mirror 17 is transmitted through the laser medium 3 and the heat conductive substrate 5 to receive the laser beam 11e that is diverged, and the laser beam 11e is condensed and irradiated on the central portion O of the laser medium 3. A third spherical mirror 21 as an element is provided.
In an upper and lower space in a direction orthogonal to the plate surface of the laser medium 3, for example, an optical resonator 25 including an output mirror 23a as an optical element constituted by a concave mirror and a total reflection mirror 23b is provided.
Is provided.

In the above configuration, the excitation light 11a from the semiconductor laser 9 is focused on the central portion O of the laser medium 3 (YAG), and a part of the excitation light 11a is absorbed by the laser medium 3 and To excite the active substance (ytterbium ion: Yb ³⁺ ).

The excitation light 11b transmitted through the laser medium 3 is
The light is again focused on the central portion O of the laser medium 3 via the first spherical mirror 15 and the second spherical mirror 17, and a part of the excitation light 11d is absorbed by the laser medium 3 to excite the active substance in the laser medium 3 again. Here, the excitation light 11e transmitted through the laser medium 3 without being absorbed is converted into the laser medium 3 by the third spherical mirror 21.
Is condensed at the central portion O of the laser beam and travels backward through the optical path of the outward path and passes through the laser medium 3 twice from the back surface.

That is, the excitation light from the semiconductor laser 9 can pass through the laser medium 3 twice from the front surface and twice from the back surface, that is, four times in total. For this reason, the excitation density of the central portion O of the laser medium 3 becomes high, and laser oscillation at a low threshold becomes possible. The laser output is output from the output mirror 23a in the direction of the optical axis 27 of the optical resonator 25.

The arrangement of the two-dimensional optical system shown in FIG.
It is possible to arrange a plurality of sets three-dimensionally for one laser medium 3.

An optically pumped solid-state laser oscillator 2 shown in FIG.
A second embodiment in which the excitation optical systems are arranged at 120 ° intervals about the optical axis of the optical resonator is shown in FIG. Note that FIG.
Is a view as seen from the output mirror 23a side of the optical resonator 25, and the condenser lens 13, the lower first spherical mirror 15, the third spherical mirror 21, and the like are not shown. Further, the same components as those in FIG. 1 are denoted by the same reference numerals, and detailed description thereof is omitted.

According to the second embodiment, by arranging three sets of laser excitation systems so as to surround the laser medium 3, it is possible to easily increase the excitation energy density and increase the laser output. Further, since the laser medium 3 has a shape that allows the oscillated laser light to pass from the front surface to the back surface, it is possible to arrange this system in a plurality of stages in series.

FIG. 3 shows a third embodiment, which is an example of a laser oscillator in which the above-described light-pumped solid-state laser oscillator 1 of FIG. 1 or the light-pumped solid-state laser oscillator 2 of FIG. 2 is connected in series. The same parts as those in FIGS. 1 and 2 are denoted by the same reference numerals, and detailed description is omitted.

In the third embodiment, a plurality (two in the embodiment) of laser media 3 are provided on the optical axis 27 of the optical resonator at a distance, and the plurality (two in the embodiment) of the laser medium 3 is provided. An excitation light source 9 for exciting the laser medium 3 and an excitation optical system are separately provided.

With the configuration shown in FIG. 3, a laser output substantially proportional to the number of stages of the connected laser oscillators 1 can be obtained.

[0031]

According to the first aspect of the present invention, the excitation light is transmitted through the center of the laser medium two times from the front and back, a total of four times, so that the excitation density (excitation energy density) of the center of the laser medium is obtained. And the laser oscillation at a low threshold becomes possible. Also, since the optical resonator has an optical axis substantially perpendicular to the laser medium, it is possible to connect the resonators in series to create a higher-power system.

According to the second aspect of the present invention, in addition to the effect of the first aspect of the present invention, it is possible to easily produce a high-output system.

According to the third aspect of the present invention, by cooling the laser medium, the thermal lens effect and the like can be suppressed, a stable output can be obtained, and the mode fluctuation can be suppressed.

According to the fourth aspect of the present invention, an excitation light source is individually provided for a plurality of laser media, and a plurality of laser media are arranged in series to constitute an optical resonator. Can be excited. Therefore, an oscillator having a necessary high output can be easily manufactured.

[Brief description of the drawings]

FIG. 1 is an explanatory view of a first embodiment of an optically pumped solid-state laser oscillator according to the present invention.

FIG. 2 is an explanatory diagram of a second embodiment of the optically pumped solid-state laser oscillator according to the present invention.

FIG. 3 is an explanatory diagram of a third embodiment of the optically pumped solid-state laser oscillator according to the present invention.

FIG. 4 shows a conventional optically pumped solid-state laser oscillator (Apllied Phys.)
ics B58, 365-372 (1994)).

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Optically pumped solid-state laser oscillator 3 Laser medium 5 Thermal conductive substrate 7 Heat sink 9, 9 (ac) Semiconductor laser 11 (ae) Excitation laser beam 13 Condensing lens 15 First spherical mirror 17, 17 (a-) c) Second spherical mirror 19 Aperture 21 Third spherical mirror 23a Output mirror 23b Total reflection mirror 25 Optical resonator 27 Optical axis O Central part of laser medium

Claims (4)

[Claims] In an optically-pumped solid-state laser oscillator using a semiconductor laser as an excitation light source for exciting a laser medium, an optical element for condensing excitation light from the excitation light source into the laser medium is provided in a space above the laser medium. And an excitation optical system closed by the three optical elements (upper and lower) and the excitation light source, and the laser is provided in an upper space and a lower space of the laser medium. An optically-pumped solid-state laser oscillator comprising an optical element constituting an optical resonator having an optical axis substantially perpendicular to a medium. 2. The optical pump according to claim 1, wherein the laser medium is formed in a plate shape, and a plurality of sets of the excitation light source and the excitation optical system for exciting the laser medium are provided. Solid state laser oscillator. 3. An optically pumped solid-state laser oscillator according to claim 1, wherein said laser medium is provided on a transparent thermal conductive substrate, and said thermal conductive substrate is supported on a heat sink. . 4. A method according to claim 1, wherein a plurality of laser media are provided on the optical axis of said optical resonator at a distance, and said excitation light source for exciting said plurality of laser media and an excitation optical system are separately provided. The optically-pumped solid-state laser oscillator according to claim 1.