JPH0430484A - Solid-state laser - Google Patents

Abstract

PURPOSE:To improve the resonator and the exciting optical system of a solid- state laser in degree of freedom of design by a method wherein miniature laser medium members which are easily obtained and processed are used to easily secure more exciting stages without deteriorating them in utilization. CONSTITUTION:At least, a laser medium pellet 21 is a laser medium member and made to serve as an active mirror, and laser rays L1 are returned by the pellet 21. The active mirror has two functions, where it functions as both a laser medium and a reflective mirror, and exciting light rays L2 are made to impinge on the rear of the pellet 21 overlapping each other along the optical axis of a zigzag optical path LP to excite the pellet 21, whereby the laser rays L1 are resonated to output laser output rays L3. In this case, the pellets 21 are arranged so as to cover the optical path LP and formed into plates of Nd:YAG or YLF(YLiF4). By this setup, a solid-state laser of this design can output laser rays of high power executing the multistage excitation of laser rays, and the resonator and the exciting optical system of the laser can be enhances in degree of freedom of design.

Description

[Detailed description of the invention] Industrial applications This invention relates to improvements in solid state lasers.

Conventional edge-pumped laser-pumped solid-state lasers have a great advantage over side-pumped laser-pumped solid-state lasers in that they are easier to obtain the TEMoo mode. However, in this end-pumped laser-pumped solid-state laser, it is structurally difficult to use a plurality of pumping lights in order to increase its output.

Therefore, in order to increase the output power while maintaining the advantages of edge-pumped solid-state lasers, the tandem multi-stage pumped laser resonator shown in Figure 7 and the multi-edge pumped laser resonator shown in Figure 8 have been put into practical use. .

In the former, excitation light beams 1 and 2 are incident on solid-state laser rods 3 and 4, respectively, and resonated using a folding mirror 5.6 and an output mirror 7 to extract solid-state laser output light 8.

In the latter, excitation light is applied to a Nd, YAG crystal 11 using an optical fiber 12. 13 is an output mirror, and 14 is a semiconductor laser.

Problems to be Solved by the Invention The optical system of the laser resonator shown in Fig. 7 requires a large number of components to make up the optical system, and as the number of excitation stages increases, the arrangement and alignment become complicated, and the entire optical system becomes complicated. becomes a big thing. Also, the excitation system and laser rod 3
．． Insertion of the folding mirror 5.6 between the excitation end faces of 4 increases the distance between the excitation system and the excitation end face, which reduces the degree of freedom in design.

On the other hand, the optical system of the laser resonator shown in FIG. 8 corrects the drawbacks of the tandem laser resonator. However, a large and homogeneous Nd, YAG crystal 11 is required. This large, homogeneous crystal is difficult to produce, making it difficult to obtain and expensive.

Furthermore, since the beam diameter of an edge-pumped semiconductor laser-excited solid-state laser is generally very small compared to the size of the crystal that is the laser base material, the base material utilization efficiency is extremely poor.

Purpose of the Invention The present invention uses a small laser medium member that is easily available and easy to process, to easily secure a larger number of excitation stages without sacrificing utilization efficiency, and to improve the design of the laser resonant part and excitation optical system. The purpose is to provide a solid-state laser that can increase the degree of freedom.

Summary of the Invention The gist of the present invention is a solid-state laser as set forth in the claims.

Means to solve problems Please refer to FIG.

At least one laser medium pellet 21 is a laser medium member. This laser medium pellet 21 is used as an active mirror to return the laser beam L1. An active mirror is a mirror that functions both as a laser medium and as a reflecting mirror. The excitation light L2 is superimposed and excited along the optical axis of a zigzag-shaped folded optical path from behind the laser medium pellet 21. As a result, the laser light L1 is resonated and outputs a laser output light L3.

Example 1 Refer to the solid state laser in FIG.

[Intermediate Medium] The intermediate medium 20 may be any medium that allows laser light to pass therethrough. For example, it has a rectangular shape and is made of optical glass such as isotropic crown glass or flint glass.

The intermediate medium 20 is isotropic and has little absorption loss and scattering loss with respect to the laser beam L1 and the excitation light L2.

The intermediate medium 20 has a plurality of laser medium pellets 21 on one and the other wide surfaces, respectively. The upper and lower surfaces are parallel. This laser medium pellet 21 has an absorption length that allows a gain necessary for oscillation of the laser beam L1 to be obtained and a clear aperture that is large enough to ignore diffraction loss.

[Laser medium pellet 21] Laser active medium pellet or laser medium pellet 21
is arranged so that the folded optical path LP has a force /< -. The pellet 21 is, for example, plate-shaped, such as Nd:YAG or Y
Made of LF (YLiF4). Pellet 21 is used as an active mirror. Laser medium pellet 21
The side end surface 22 of the laser beam L1 is coated to have a high reflection rate for the laser beam L1 and a high transmittance for the excitation light L2. This side end surface 22 has a zigzag-shaped folded optical path LP.
form. The side end surface 23 is coated with a non-reflective coating for laser light between the intermediate medium 20 and the laser medium pellet 21.

The high reflection mirror 60 is, for example, optical glass coated with a coating that has a high reflectivity for the laser output light, and the output mirror 61 is, for example, a half mirror that does not absorb or scatter the laser output light. A half-characteristic reflective film is applied to the inside of the material. A high reflection mirror 60 is arranged corresponding to one surface of the intermediate medium 30, and an output mirror 61 is arranged corresponding to the other surface of the intermediate medium 20.

[Excitation Light L2] Each excitation light L2 of the semiconductor laser 40.43 is superimposed on the laser medium pellet 21 and the intermediate medium 2o along the optical axis of the optical path 31 of the folded optical path. Similarly, each excitation light L2 of the semiconductor lasers 41 and 44 is also irradiated along the optical axis of the optical path 32. Furthermore, each excitation light L2 of the semiconductor lasers 42 and 44 is also irradiated along the optical axis of the optical path 33. This excitation light L2 has a wavelength in the absorption wavelength range of the laser medium. The excitation light L2 is, for example, a laser diode (LD
) or emitted by a dye laser. The wavelength of the laser output is 1.06 μm for Nd;YAG and 1-053 pm for YLF.

The oscillation operation semiconductor lasers 40 to 45 are driven to superimpose the excitation light L2. The angle of incidence of this excitation light L2 is such that the direction of the internally reflected light beam and the refracted light beam coincide. For example, it is an angle determined by Snell's law between the axis of the laser beam L1, the excitation wavelength, and the refractive index of the laser active material. Thereby, the laser beam L1 resonates between the output mirror 61 and the high reflection mirror 60 via the zigzag optical path LP, and is excited in multiple stages by a plurality of excitation beams L2. As a result, the output of the laser light output L1 is increased and outputted as the laser output light L3.

Example 2 See Figure 2.

In this second embodiment, two plate-like mirror-type laser medium members 105 and 106 are arranged facing each other. Side end surfaces 12 of laser medium members 105 and 106, also called laser base materials
2 is highly reflective for the laser beam L1, and the excitation light L
For No. 2, a coating treatment with high transmittance is used. Between the laser medium members 105 and 106 is an air layer 130 as an intermediate medium. Laser base material 105, 10
6 is made of Ndi:YAG, for example. air layer 130
The difference between the refractive index of the laser medium member 105 and the refractive index of the laser medium members 105 and 106 is large, and it is necessary to apply an anti-reflection coating. If an intermediate medium made of glassy La5FQ5 or the like is provided as a support layer for the laser medium members 105 and 106 instead of this air layer, the refractive index of both will be reduced, and the reflection and scattering loss at the interface will be reduced. Become.

In this way, by dividing the laser base material and making the intermediate layer an inactive layer, we can save the laser base material in the part that does not provide output gain of the laser output light, reduce loss due to reabsorption, and further reduce absorption. It is also possible to reduce the accompanying thermal distortion and eliminate mutual interference of thermal distortion.

Example 3 See Figure 3.

A laser medium pellet 221 is placed on one surface of a glass mirror laser medium member 220 to be used as an active mirror. The side end surface 222 of the laser medium pellet 221 is coated to have high reflection for the laser beam L1 and high transmittance for the excitation light L2. Further, the side end surface 225 of the holding glass portion 220 is coated so that the laser beam L1 from the high-reflection mirror 60 is transmitted through the incident portion thereof, and is highly reflective to the laser beam L1 at other portions. Semiconductor lasers 40 to 42 are provided corresponding to the laser medium pellet 221.

Example 4 Please refer to FIG.

Unlike the third embodiment shown in FIG. 3, excitation light L2 from the semiconductor lasers 43 to 45 is superimposed toward the laser medium pellet 221 from the holding glass portion 220 side. Note that the holding glass part 220
The side end surface 225a is configured such that the laser beam L1 from the high-reflection mirror 60 is transmitted through the incident area, and is highly reflective for the laser beam L1 at other locations, and is transparent for the excitation light L2. coated.

Example 5 Please refer to FIG.

Three sets of semiconductor lasers 40.46.41.47.42.4
8 is provided. This allows the number of excitation stages to be further increased and the output to be increased. The side end surface 225b of the holding glass portion 220 is coated so as to transmit the laser beam L1 from the high-reflection mirror 60 at a location where it is incident, and to highly reflect the laser beam L1 at other locations.

Example 6 Please refer to FIG.

A plurality of laser medium pellets 21 and one laser medium member 105 are combined.

By the way, the small solid-state laser capable of multi-stage excitation as described above can be used, for example, as a light source for an ophthalmological photocoagulation device or a laser processing device.

Effects of the Invention Using a small laser medium member or laser base material that is easily available and easy to process, laser light can be excited in multiple stages to obtain high-output laser output light.

Further, the turning pitch of the laser optical path and the number of excitation stages can be set without being restricted by the size of the laser medium member or the laser base material, increasing the degree of freedom in designing the laser resonant portion and the excitation optical system.

[Brief explanation of drawings]

FIG. 1 is a diagram showing Example 1 of the solid-state laser of the present invention, FIGS. 2 and 3 are diagrams showing Examples 2 and 3, and FIGS. 4 to 6 are diagrams showing Examples 4 to 6. FIGS. 7 and 8 are diagrams showing conventional examples. 0......Intermediate medium 1......Laser medium pellet 0-45.
・・Semiconductor laser beam・・・・・・・Laser beam 2・・・・・・・・・・・・Excitation light 3・・・・・・・・・Laser output light beam

Claims (1)

[Claims] A solid-state laser that emits laser output light by superimposing excitation light along the optical axis of a zigzag-shaped folded optical path to excite and resonate the laser light, and has both the function of a laser medium and the function of a reflecting mirror. It has at least one laser medium member (21, 105, 106, 221) that is used as a mirror to fold back the laser beam (L1), and the optical axis of the folded optical path with respect to the laser medium member (21, 105, 106, 221). A solid-state laser characterized in that a laser beam (L1) is excited and resonated by superimposing excitation light (L2) along the .