JPH0745892A - Solid-state laser equipment - Google Patents

Abstract

PURPOSE:To obtain highly efficient laser motion by making polarization of a semiconductor laser beam co-axial with the c-axis direction of a Nd:YVO4 crystal without a spatial transfer of the semiconductor laser or the Nd:YVO4 crystal in semiconductor laser excitation solid-state laser equipment using the Nd:YVO4 crystal as a solid-state laser medium. CONSTITUTION:A 1/2 wavelength plate 4, a condensing lens 2, a Nd:YVO4 crystal 5 with a 1% Nd concentration as an anisotropic solid-state laser medium, and a resonator mirror 3 are arranged in this order from the semiconductor side on an optic axis of excitation light emitted from a semiconductor laser 1, and the resonator mirror 5a is formed by coating the excitation side edge surface of the Nd:YVO4 crystal. This enables polarization of excited light turn around by the 1/2 wavelength plate 4 in line with the c-axis direction of the Nd:YVO4 crystal.

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 device, and more particularly to a solid-state laser device for guiding light from a semiconductor laser directly or through an optical fiber and exciting the solid-state laser medium with this light as an end face. Is.

[0002]

2. Description of the Related Art Nd: one of anisotropic solid-state laser crystals
YVO ₄ has a larger absorption coefficient at the oscillation wavelength of a semiconductor laser than conventional Nd: YAG, and is attracting attention as a solid-state laser medium suitable for pumping a semiconductor laser. Nd: YVO ₄ is a uniaxial crystal and has different absorption coefficients in the c-axis direction and the a-axis direction of the crystal. The size ratio is about 4 to 1 in the vicinity of 809 nm, which corresponds to the oscillation wavelength of the GaAs semiconductor laser, and the absorption coefficient in the c-axis direction is large.

On the other hand, generally, the polarized light of a semiconductor laser is linearly polarized light in a direction substantially parallel to the active layer. Therefore, the polarization of the semiconductor laser should be N
It is desirable to excite the d: YVO ₄ crystal so that it coincides with the c-axis direction (see, for example, JP-A-4-137775). However, since the active layer, which is the light emitting part of the semiconductor laser, is very small, the polarization of the semiconductor laser is changed to Nd: YVO ₄
It is not easy to exactly match the c-axis direction of the crystal. In fact, when assembling a laser device, a spatial movement mechanism for a semiconductor laser or a solid-state laser crystal must be provided, and there is a drawback that the device becomes complicated as a whole.

[0004]

SUMMARY OF THE INVENTION In view of the above problems of the prior art, the main object of the present invention is to provide a semiconductor laser or N
We provide a solid-state laser device that can achieve efficient laser operation by perfectly matching the polarization of the semiconductor laser with the c-axis direction of the Nd: YVO ₄ crystal without requiring spatial movement of the d: YVO ₄ crystal. To do.

[0005]

According to the present invention, such a purpose is to resonate a semiconductor laser, an anisotropic solid-state laser medium end-pumped by pumping light from the semiconductor laser, and a pair of mirrors. In a solid-state laser device having a container, an axis between the semiconductor laser and the anisotropic solid-state laser medium for polarization-rotating the excitation light to increase the absorption coefficient of the anisotropic solid-state laser crystal. This is achieved by providing a solid-state laser device characterized by disposing a half-wave plate for matching the directions. In particular, the anisotropic solid-state laser medium is preferably a Nd: YVO ₄ laser crystal.

[0006]

[Function] The half-wave plate placed between the semiconductor laser and the Nd: YVO ₄ crystal is made of a transparent anisotropic crystal such as quartz. When propagating, a phase velocity difference occurs in each axial direction due to the difference in refractive index depending on the axial direction. Since the fast axis in the direction in which light travels fast and the slow axis in the direction in which light slows are orthogonal to each other, and the phase difference between the fast axis and the slow axis in the half-wave plate is exactly π, The component that oscillates in the slow axis direction of light is π compared to the fast axis direction.
Only the phase is delayed. For example, if the polarization of the incident light is 45 ° with respect to the fast axis of ½ wavelength, the polarization of the emitted light will rotate exactly 90 °. Generally, when the angle formed by the polarization direction of incident light and the fast axis direction of the half-wave plate is θ, the polarization of emitted light is rotated by 2θ. For example, the Nd: YVO ₄ crystal has an a-axis cut, and the polarization direction of the semiconductor laser is
If the c-axis of Nd: YVO ₄ crystal forms 45 °,
The angle formed by the semiconductor laser and the fast axis of the half-wave plate is 22.
If it is set to 5 °, the polarization of the semiconductor laser can be rotated by 45 °, and the polarization of the semiconductor laser can be perfectly matched with the c-axis direction of the Nd: YVO ₄ crystal.

In this way, the semiconductor laser and Nd: YV
The polarization of the semiconductor laser can be perfectly matched to the c-axis direction of the Nd: YVO ₄ crystal without requiring spatial movement of the O ₄ crystal.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT A preferred embodiment of the present invention will now be described in detail with reference to the accompanying drawings.

FIG. 1 is a schematic perspective view showing the structure of a solid-state laser device in an embodiment to which the present invention is applied. In the present embodiment, as shown in FIG. 1, on the optical axis of the excitation light emitted from the semiconductor laser 1, the half-wave plate 4, the condenser lens 2, and the anisotropy from the semiconductor laser 1 side. An Nd: YVO ₄ crystal 5 having a Nd concentration of 1% as a solid-state laser medium and a resonator mirror 3 are arranged in this order. Nd: YVO ₄ crystal 5
A resonator mirror 5a formed by coating is provided on the end face on the excitation side of the.

The Nd: YVO ₄ crystal 5 has a size of 3 × 3 × 1 ^t mm and is cut in the ac plane. The polarization of the semiconductor laser 1 and the c-axis of the Nd: YVO ₄ crystal 5 are set to be about 45 °. A half-wave plate 4 which functions at the wavelength of the semiconductor laser 1 is arranged between the semiconductor laser 1 and the condenser lens 2, and the half-wave plate 4 is used to change the polarization of the semiconductor laser 1. The Nd: YVO ₄ crystal 5 was rotated so as to coincide with the c-axis having a large absorption coefficient.

Excitation light (8
09Nm) passes through half-wave plate 4 first, is collected by the condenser lens 2 from the circular polarization, Nd: irradiates the YVO ₄ crystal 5, Nd: YVO ₄ to excite the crystal 5, basic laser beam Generates spontaneous emission light (1064 nm) at a wavelength. The spontaneous emission light emitted from the Nd: YVO ₄ crystal 5 is reflected by the resonator mirror 3,
Returning to the Nd: YVO ₄ crystal 5 in the reverse direction of the original optical path, where it is amplified by stimulated emission, reflected by the resonator mirror 5a on the end face on the excitation side of the Nd: YVO ₄ crystal 5, and inside the resonator. Make a round trip. In this way, if the resonator mirrors 5a and 3 satisfy the conditions for laser oscillation, laser oscillation occurs. The oscillated basic laser light is emitted from the output mirror 3 on the output side end face.

Adjustment of the arrangement of the half-wave plate 4 is performed by Nd: YVO ₄
The output can be maximized while observing the magnitude of the basic laser oscillation output of. For example, when the excitation input was 750 mW, 350 mW was obtained as the fundamental laser oscillation output of Nd: YVO ₄ . This is an output improvement of 30% as compared with the case where the half-wave plate is not inserted.

In this embodiment, Nd: YVO ₄ crystal is used as the laser medium, but other anisotropic crystal may be used. The half-wave plate 4 may be installed anywhere between the semiconductor laser 1 and the Nd: YVO ₄ crystal 5.

[0014]

As described above, according to the solid-state laser device of the present invention, the polarization of the semiconductor laser and the Nd: YVO ₄ crystal can be polarized in the c-axis direction of the Nd: YVO ₄ crystal without requiring spatial movement of the semiconductor laser and the Nd: YVO ₄ crystal. Can be perfectly matched with, and efficient laser operation can be obtained.

[Brief description of drawings]

FIG. 1 is a perspective schematic view showing a configuration of a solid-state laser device to which the present invention is applied.

[Explanation of symbols]

1 semiconductor laser 2 condenser lens 3 resonator mirror 4 1/2 wavelength plate 5 Nd: YVO ₄ crystal 5a resonator mirror

Claims (2)

[Claims] 1. A semiconductor laser, and an anisotropic solid-state laser medium that is end-pumped by pumping light from the semiconductor laser,
In a solid-state laser device having a resonator composed of a pair of mirrors, the excitation light is polarized and rotated between the semiconductor laser and the anisotropic solid-state laser medium to absorb the anisotropic solid-state laser crystal. 1 / to match the axial direction where the coefficient is large
A solid-state laser device having a two-wave plate. 2. The solid-state laser device according to claim 1, wherein the anisotropic solid-state laser medium is an Nd: YVO ₄ laser crystal.