JPH06209132A - Solid-state laser - Google Patents

Abstract

PURPOSE:To enable one of the two oscillation lines to be selected by a simple means without incurring the resonator insertion loss at all within a solid-state laser pumping anisotropical laser crystal. CONSTITUTION:Semiconductor laser 11 and focussing lens 12 as pumping means are fixed on a vertically shifting mount 15 by driving a precision screw 18 so that the relative positions od the semiconductor laser 11 and the focussing lens 12 to Nd:YLF crystal 13 and a resonator mirror 14 may be changed by vertically shifting the mount 15 thereby enabling either normal beams or abnormal beams only emitted from the Nd:YLF crystal 13 to be selectively oscillated.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a solid-state laser, and more specifically, an anisotropic laser crystal is used as a laser medium to selectively extract two kinds of laser beams having different polarization directions and different wavelengths. It relates to solid-state lasers.

[0002]

2. Description of the Related Art As disclosed in, for example, Japanese Unexamined Patent Publication (Kokai) No. 62-189783, a solid-state laser is known in which a laser crystal doped with a rare earth element such as neodymium (Nd) is pumped by a semiconductor laser or the like. This solid-state laser basically comprises the above laser crystal, pumping means for making pumping light incident on the laser crystal, and a resonator mirror for oscillating a solid-state laser beam emitted from the laser crystal.

In this type of solid-state laser, an anisotropic crystal such as LiYF ₄ (YLF) may be used as a laser crystal. In that case, generally, two oscillation lines are formed in one oscillation wavelength band. Exists. For example, the above YLF doped with Nd (hereinafter referred to as Nd: YLF)
In the 1.0 μm band, a so-called σ-polarized laser beam having a wavelength of 1053 nm and a π-polarized wavelength of 10 μm are used.
A laser beam of 47 nm can be oscillated, and similarly 1313 nm (σ polarized light) and 1321 n in the 1.3 μm band.
There can be two oscillating lines of m (π-polarized). This is because ordinary rays and extraordinary rays oscillate.

Therefore, when using such an anisotropic laser crystal, it is generally necessary to take measures to obtain a desired single oscillation line. For example, OPTICS L
ETTERS (Optics Letters) /Vol.11, N
In o.4 / April 1986, a Brewster plate was inserted into the resonator of a solid-state laser using an anisotropic laser crystal, and this Brewster plate was rotated 90 ° to create two oscillation lines. It is shown to select one of them.

[0005]

However, the conventional solid-state laser using the Brewster plate has a problem that a resonator insertion loss due to the Brewster plate is large and it is difficult to perform high-efficiency oscillation.

Further, in this solid-state laser, a complicated mechanism for rotating the Brewster plate is necessary, and further the readjustment of the resonator mirror is required along with the rotation, so that the structure is likely to be complicated and the adjustment is also difficult. It has the drawback of being difficult.

The present invention has been made in view of the above circumstances, and provides a solid-state laser having a simple structure which can easily obtain a desired single oscillation line by using an anisotropic laser crystal. The purpose is to do.

[0008]

A first solid-state laser according to the present invention is, as described in claim 1, a solid-state laser comprising a laser crystal as described above, pumping means, and a resonator mirror. The laser crystal is arranged such that its crystal axis forms an angle with the laser oscillation axis, while the pumping means, the laser crystal and the resonator mirror are selected only from one of the ordinary ray and the extraordinary ray emitted from the laser crystal. It is characterized in that means for relatively linearly moving so as to oscillate is provided.

The second solid-state laser according to the present invention is
As described in claim 2, a laser crystal similar to the above,
In a solid-state laser comprising a pumping means and a resonator mirror, a laser crystal is arranged such that its crystal axis forms an angle with the laser oscillation axis, while the resonator mirror, the laser crystal and the pumping means It is characterized in that means for relatively linearly moving is provided so that only one of the ordinary ray and the extraordinary ray emitted from the crystal selectively oscillates.

[0010]

When the laser crystal is arranged in such a direction that its crystal axis forms an angle with the laser oscillation axis as described above, the solid laser beam emitted from the laser crystal produces a composite laser beam of the laser crystal. Due to the refractive property, it is composed of ordinary rays and extraordinary rays. The ordinary ray and the extraordinary ray have different wavelengths such as 1.313 μm and 1.321 μm when the above-mentioned Nd: YLF is used. Therefore, as in the first solid-state laser, the relative position between the pumping means and the laser crystal and the resonator mirror is changed, or like the second solid-state laser, the resonator mirror and the laser crystal and the pumping means are relative to each other. When the position is changed, the optical path between the resonator mirrors is changed so that one of the state where the ordinary ray oscillates and the state where the extraordinary ray oscillates can be selectively created.

As described above, in the solid-state laser of the present invention, one of the two types of oscillation lines (and accordingly the polarization direction) can be selectively obtained. Compared with the means for rotating the Brewster plate, the means for linearly moving the laser crystal and the resonator mirror or the means for linearly moving the resonator mirror and the laser crystal and pumping means The mechanism is simpler. Therefore, the solid-state laser of the present invention has a simpler structure, lower cost, and easier adjustment than the conventional device in which the Brewster plate is rotated to select the oscillation line.

And in the solid-state laser of the present invention,
Since a new element such as a Brewster plate is not inserted in the resonator for selecting the oscillation line, there is no resonator insertion loss due to such an element, and therefore high efficiency oscillation is possible.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in detail below based on the embodiments shown in the drawings. FIG. 1 shows a laser diode pumped solid state laser according to a first embodiment of the present invention. The solid-state laser includes a semiconductor laser 11 that emits a laser beam 10 as pumping light, and a condenser lens 12 that focuses the laser beam 10 that is divergent light.
It has an Nd: YLF crystal 13 which is an anisotropic laser crystal, and a resonator mirror 14 arranged on the front side (right side in the figure) of this Nd: YLF crystal 13.

Here, the Nd: YLF crystal 13 is cut so that the crystal a-axis and the c-axis form an angle with respect to the laser oscillation axis A. This angle is an angle θ with respect to the a-axis, and is usually a value in the range of 20 ° to 70 °. Further, the semiconductor laser 11 is temperature-controlled to a predetermined temperature by a Peltier element and a temperature-adjusting circuit (not shown).

On the other hand, the semiconductor laser 11 and the condenser lens 12 constituting the pumping means are fixed to a common mount 15. A plurality of guide rods 16 extending in the vertical direction in the figure are fixed to the lower surface of the mount 15, and these guide lots 16 are inserted into a holding member 17. In addition, a precision screw 18 is rotatably held on this holding member 17,
The tip of the precision screw 18 is screwed into a nut portion 19 fixed to the mount 15. Therefore, when the precision screw 18 is rotated forward and backward, the nut portion 19 is screwed back and forth accordingly, so that the mount 15 moves in the vertical direction in the figure. When the mount 15 moves in this way, the semiconductor laser 11 and the condenser lens 12 move to the Nd: YLF crystal 13 and the resonator mirror.
It moves relative to 14 in the vertical direction in the figure.

The Nd: YLF crystal 13 emits a laser beam 20 having a wavelength of 1321 nm or 1313 nm (this point will be described later) when Nd atoms are excited by the laser beam 10 having a wavelength of 795 nm. At the light incident end face 13a of the Nd: YLF crystal 13, a wavelength of 7
The 95 nm pumping laser beam 10 is well transmitted while the laser beam 20 having a wavelength of 1321 nm or 1313 nm is well reflected. Further, while the pumping laser beam 10 is well reflected on the mirror surface 14a of the resonator mirror 14,
A coating that partially transmits the laser beam 20 is provided. Therefore, the solid-state laser beam 20 resonates between the mirror surface 14a of the resonator mirror 14 and the end surface 13a of the Nd: YLF crystal 13 and a part thereof is extracted from the resonator mirror 14.

Next, selection of the oscillation line will be described.
As described above, when the precision screw 18 is rotated to move the mount 15 in the vertical direction, the incident position of the pumping laser beam 10 on the Nd: YLF crystal 13 is changed. In the present embodiment, the laser beam 10 is displayed as a solid line in the figure with Nd:
When it is incident on the YLF crystal 13, an ordinary ray oscillates and a wavelength of 1
A 313 nm solid-state laser beam 20 is obtained. At this time, the laser beam 20 becomes so-called σ-polarized light (the polarization direction in the figure is a direction perpendicular to the paper surface). On the other hand, when the laser beam 10 is made incident on the Nd: YLF crystal 13 in the state shown by the broken line in the figure, an extraordinary ray oscillates and a solid-state laser beam 20 having a wavelength of 1321 nm is obtained. At this time, the laser beam 20 becomes so-called π-polarized light (the polarization direction in the figure is parallel to the paper surface). The reason why the oscillation line can be selected as described above is as described in detail above.

Next, a second embodiment of the present invention will be described with reference to FIG. In FIG. 2, the same elements as those already described in FIG. 1 are denoted by the same reference numerals as those in FIG. 1, and duplicate description thereof will be omitted. In the solid-state laser of the second embodiment, Nd:
The light emitting end surface 13b of the YLF crystal 13 is polished into a convex surface forming a part of a spherical surface, and constitutes a resonator mirror together with the light incident end surface 13a. On this end face 13b, the resonator mirror of FIG.
The same coating as that applied to the 14 mirror surfaces 14a is applied.

On the other hand, the semiconductor laser 11 as pumping means is arranged close to the flat light incident end face 13a of the Nd: YLF crystal 13. And this semiconductor laser
11 is fixed to a mount 15 similar to that of FIG. 1, and can be moved in the vertical direction in the figure by rotating a precision screw 18.

In this embodiment, when the laser beam 10 is incident on the Nd: YLF crystal 13 in the state shown by the solid line in the figure, an ordinary ray oscillates and a solid laser beam having a wavelength of 1313 nm is emitted.
20 (σ polarized light) is obtained, on the other hand, when the laser beam 10 is incident on the Nd: YLF crystal 13 in the state shown by the broken line in the figure, an extraordinary ray oscillates and the solid laser beam 20 (π polarized) having a wavelength of 1321 nm is generated. can get.

In the embodiment described above, Nd: Y
The LF crystal 13 is fixed and the pumping means is moved. On the contrary, the pumping means is fixed and the Nd: YLF crystal 13 is fixed (in the first embodiment, the resonator mirror 14 is also included). You may make it move.

Next, a third embodiment of the present invention will be described with reference to FIG. The solid-state laser of the third embodiment is
It differs from the solid-state laser of FIG. 1 only in that the semiconductor laser 11 and the condenser lens 12 are held by a fixed mount (not shown), and the resonator mirror 14 is fixed by a vertically movable mount 15.

In this structure, when the precision screw 18 is rotated to move the mount 15 in the vertical direction, the relative position of the resonator mirror 14 with respect to the semiconductor laser 11, the condenser lens 12 and the Nd: YLF crystal 13 changes. Therefore, the oscillation line of the laser beam 20 can be selected.
In this embodiment, when the resonator mirror 14 is set to the position indicated by the solid line in the figure, the ordinary ray oscillates and the solid-state laser beam 20 (σ-polarized) having a wavelength of 1313 nm is obtained. On the other hand, when the resonator mirror 14 is set to the position indicated by the broken line in the figure, an extraordinary ray oscillates and the solid-state laser beam 20 having a wavelength of 1321 nm
(Π polarized light) is obtained.

The embodiment in which the oscillation line is selected in the 1.3 μm band has been described above. However, the oscillation line in the 1.0 μm band of the Nd: YLF crystal 13, that is, 1053 nm (σ polarization) of ordinary ray oscillation and extraordinary ray oscillation. Of 104
It is also possible to select one of 7 nm (π-polarized light).

The present invention also relates to the Nd: YLF described above.
Laser crystal other than Nd: MgO: Li
It can also be applied to a solid-state laser using NbO ₃ , Nd: YVO ₄ , LNP, etc., and has the same operation and effect.

Furthermore, the present invention can be similarly applied to a solid-state laser in which a crystal of a nonlinear optical material is arranged in a resonator to convert the wavelength of a solid-state laser beam into a second harmonic wave or the like.

[Brief description of drawings]

FIG. 1 is a schematic side view showing a solid-state laser according to a first embodiment of the present invention.

FIG. 2 is a schematic side view showing a solid-state laser according to a second embodiment of the present invention.

FIG. 3 is a schematic side view showing a solid-state laser according to a third embodiment of the present invention.

[Explanation of symbols]

 10 Laser beam for pumping 11 Semiconductor laser 12 Condenser lens 13 Nd: YLF crystal 14 Resonator mirror 15 Mount 16 Guide rod 17 Holding member 18 Precision screw 20 Solid-state laser beam

Claims (2)

[Claims] 1. An anisotropic laser crystal doped with a rare earth element such as neodymium, pumping means for causing pumping light to enter the laser crystal, and a resonator mirror for oscillating a solid laser beam emitted from the laser crystal. In the solid laser, the laser crystal is arranged such that its crystal axis forms an angle with the laser oscillation axis, and the pumping means, the laser crystal and the resonator mirror are ordinary rays emitted from the laser crystal. And a means for relatively linearly moving so that only one of the extraordinary rays oscillates selectively. 2. An anisotropic laser crystal doped with a rare earth element such as neodymium, pumping means for causing pumping light to enter the laser crystal, and a resonator mirror for oscillating a solid laser beam emitted from the laser crystal. In the solid laser, the laser crystal is arranged such that its crystal axis forms an angle with the laser oscillation axis, while the resonator mirror, the laser crystal and the pumping means are the ordinary rays emitted from the laser crystal. And a means for relatively linearly moving so that only one of the extraordinary rays oscillates selectively.