JPH0730182A - Solid laser device - Google Patents

Abstract

PURPOSE:To obtain a second harmonic light with polarization in a free direction regardless of the placement of a non-linear optical crystal in a solid laser device with a non-linear optical crystal for generating a second harmonic light as light emitted from a resonator. CONSTITUTION:A focusing lens 2 from the side of a semiconductor laser 1, Nd:YVO4 crystal 5 with an Nd concentration of 1% as a solid laser medium, KTP crystal 6 as a non-linear optical crystal, a resonator mirror 3, and 1/2 wavelength plate 4 are laid out in this order on the optical axis of excitation light emitted from the semiconductor laser 1 and then a resonator mirror 5a is formed on the end face at the excitation side of Nd:YVO4 crystal 5 by coating, thus achieving polarization in horizontal direction by polarization and rotation with the 1/2 wavelength plate 4.

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 in which light from a semiconductor laser is guided directly or by an optical fiber, and the solid-state laser medium is end-pumped by using this as excitation light.

[0002]

2. Description of the Related Art Conventionally, a solid-state laser medium such as an Nd: YAG crystal is placed between a pair of mirrors facing each other in a resonator. There is a solid-state laser device of the type that irradiates the solid-state laser medium to excite the solid-state laser medium, and this is known as a laser light source that is easier than a solid-state laser device of the type that uses a rare gas lamp or the like. Especially, the second such as Nd: YAG laser
Harmonic light has high utility value as a light source for optical recording and optical measurement.

In order to generate the second harmonic light, a nonlinear optical crystal such as KTP (KTiOPO ₄ ) is used, and the polarization of the second harmonic light generated there is a straight line parallel to the extraordinary optical axis direction of the KTP crystal. It becomes polarized light. Therefore, the polarization of the extracted second harmonic light is determined by the placement of the KTP crystal. On the other hand, in various applications, it is often convenient for the polarization of laser light to be horizontal or vertical.

[0004]

In view of the problems of the prior art as described above, the main object of the present invention is to provide a free direction regardless of the placement of the nonlinear optical crystal for generating the second harmonic light. It is an object of the present invention to provide a solid-state laser device that can obtain the second harmonic light having the polarization of.

[0005]

According to the present invention, there is provided a semiconductor laser, a solid-state laser crystal end-pumped by pumping light from the semiconductor laser, and a resonator including a pair of mirrors. A solid-state laser device having a resonator comprising a pair of mirrors, and a nonlinear optical crystal for generating second harmonic light as light emitted from the resonator,
This can be achieved by providing a solid-state laser device characterized in that a half-wave plate is arranged on the optical axis of the laser output light in order to rotate the polarization of the second harmonic light.

[0006]

The half-wave plate arranged on the optical axis of the laser output light is made of a transparent anisotropic crystal such as quartz. When light propagates in the anisotropic crystal, , A difference in the refractive index depending on the axial direction causes a phase velocity difference in each 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 phase of the component that oscillates in the slow axis direction of light is delayed by π compared with the direction of the fast axis direction. 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 °. In general, the polarization direction of incident light and 1/2
When the angle formed by the fast axis direction of the wave plate is θ, the polarization of the emitted light is rotated by 2θ.

For example, if the polarization direction of the second harmonic light is 45 ° with respect to the horizontal direction, the polarization direction of the second harmonic light and the angle formed by the fast axis of the ½ wavelength plate are 22.5. If the angle is set to 0, the polarization of the second harmonic light can be rotated by 45 °, and the polarization of the second harmonic light can be perfectly matched in the horizontal direction. In this way, it is possible to obtain the second harmonic light having polarized light in any direction regardless of how the nonlinear optical crystal is placed.

[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 condenser lens 2 from the semiconductor laser 1 side and the Nd concentration of 1% as a solid-state laser medium are formed.
Nd: YVO ₄ crystal 5 and KTP crystal 6 as a nonlinear optical crystal
The resonator mirror 3 and the half-wave plate 4 are arranged in this order. A resonator mirror 5a formed by coating is provided on the end surface of the Nd: YVO ₄ crystal 5 on the excitation side.

Excitation light emitted from the semiconductor laser 1 (80
(9 nm) is collected by the condenser lens 2 and irradiated on the Nd: YAG crystal 5 to excite the Nd: YAG crystal 5 to generate spontaneous emission light (1064 nm) at the fundamental laser light wavelength. The spontaneous emission light emitted from the Nd: YAG crystal 5 passes through the KTP crystal 6, is reflected by the resonator mirror 3, and travels in the opposite direction back to the Nd: YAG crystal 5, where it is stimulated emission. While being amplified by Nd: YAG
The light is reflected by the resonator mirror coating 5a provided on the end surface on the excitation side of the crystal 5 and reciprocates in the resonator. Thus, if the resonator mirrors 5a and 3 satisfy the conditions for laser oscillation, laser oscillation occurs. The oscillated basic laser light is wavelength-converted in the KTP crystal 6 which is a wavelength conversion element, becomes second harmonic light, and is emitted from the output mirror 3.

The emitted second harmonic light is polarized and rotated by the half-wave plate 4 arranged on the optical axis of the emitted light and on the emitting side of the output mirror 3, and for example, a horizontally polarized light is obtained. To be

In this embodiment, the Nd: YAG crystal is used as the laser medium, but other crystal may be used.
Although the KTP crystal is used as the nonlinear optical crystal, other crystal may be used.

[0013]

As described above, according to the solid-state laser device of the present invention, the second harmonic light having polarized light in a free direction can be obtained regardless of how the KTP crystal is placed.

[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 wave plate 5 Nd: YAG crystal 5a resonator mirror 6 KTP crystal

Claims (1)

[Claims] 1. A solid-state laser device comprising a semiconductor laser, a solid-state laser crystal end-pumped by pumping light from the semiconductor laser, and a resonator composed of a pair of mirrors, wherein a resonator composed of a pair of mirrors. And a non-linear optical crystal for generating second harmonic light as light emitted from the resonator, wherein the polarization of the second harmonic light is rotated on the optical axis of the laser output light. A solid-state laser device having a half-wave plate.