JPH04137775A - Semiconductor laser excitation solid state laser - Google Patents

Abstract

PURPOSE:To remarkably alleviate accuracy of waveform control of a semiconductor laser for reducing variation of output by using a-axis cut Nd:YVO4 as a solid state laser crystal to excite a semiconductor laser so that the optical and electric field direction becomes parallel with the c-axis of crystal. CONSTITUTION:A laser resonator is structured by providing a multilayer thin film mirror 3 of dielectric material at the end surface of the a-axis cut Nd:YVO4 crystal 4 in the side of a semiconductor laser 1 to achieve 100% reflectivity for 1064nm wavelength and a multilayer thin film of dielectric material to an output mirror 5 to achieve 80 to 98% reflectivity for 1064nm. Oscillation in the wavelength of 946nm and 1340nm can be realized as well as the wavelength of 1064nm by changing the wavelength of such multilayer thin film of dielectric material having high reflectivity. A semiconductor laser 1 is caused to provide the wavelength of 800nm to 815nm and phtoelectric field of laser beam to become parallel with the c-axis of the crystal 4. A laser beam radiated from the semiconductor laser 1 is condensed by a lens 2 and is then applied to the crystal 4. Thereby, Nd:YVO4 is excited and a laser beam of 1064nm can be extracted from an output mirror 5. As explained above, highly efficient excitation may be realized by selecting the direction of polarization for the crystal.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a laser device, and particularly to a compact and simple semiconductor laser pumped solid-state laser.

(Prior Art) Nd:YAG, Nd:YLF, and the like are often used as solid-state laser crystals in semiconductor laser-excited solid-state lasers. Since these crystals have strong absorption in the 800 nm band, it is possible to efficiently excite a solid-state laser by exciting them with a semiconductor laser having a wavelength corresponding to this. Further, by providing a second-order nonlinear optical crystal in the resonator of the semiconductor laser-excited solid-state laser, it is possible to provide a wavelength conversion laser that converts the light of the solid-state laser into harmonics with high efficiency. Regarding semiconductor laser pumped solid-state lasers, see [Laser Research, Vol. 17, No. 10 (198
9), pp. 695-704 J.

(This invention attempts to solve) However, the strong absorption bands of these solid-state laser crystals are
It has a width of only about m, and the absorption coefficient changes greatly depending on the wavelength within the absorption band. Therefore, when the wavelength of the semiconductor laser changes, the output of the solid-state laser and the output of the second harmonic also change. In order to reduce this output fluctuation, the temperature of the semiconductor laser must be controlled using a Peltier device or the like, and the oscillation wavelength of the semiconductor laser must be controlled with the required high precision. Further, since each semiconductor laser has a different oscillation wavelength, it is necessary to select one suitable for excitation of the solid-state laser.

An object of the present invention is to provide a semiconductor laser-pumped solid-state laser that significantly reduces the accuracy of wavelength control of a semiconductor laser for exciting the solid-state laser, has less output fluctuation, and widens the range of choices of semiconductor lasers to be used. It's about doing.

(Means for Solving the Problems) In the edge-pumped semiconductor laser-excited solid-state laser of the present invention,
Using a-axis cut Nd:YVO4 as a solid-state laser crystal, the direction of the optical electric field of the excitation semiconductor laser and the Nd
:It is characterized by being excited so that the crystal C axes of YVO4 are parallel. Further, the edge-pumped semiconductor laser-excited solid-state laser is characterized in that a second-order nonlinear optical crystal for generating harmonics is provided in the laser resonator.

(Function) Nd:YVO4 is a uniaxial crystal, and when used for laser oscillation, it not only polarizes in a specific direction and oscillates;
Its absorption properties are anisotropic. Semiconductor lasers generally emit light polarized in a specific direction, so efficient excitation can be achieved by selecting the polarization direction with respect to the crystal.

FIG. 3 shows the measurement results of the anisotropy of the absorption characteristics of Nd:YVO4 cut along the a-axis. For measurement, Nd concentration 1%, thickness 1m
The wavelength of the light source was set to about 809 nm, where the absorption of Nd:YVO4 is the strongest in the 800 nm band.

The horizontal axis is the angle θ between the crystal C axis and the direction of the optical electric field, and when θ is 0° or 180°, the crystal C axis and the optical electric field are parallel. The vertical axis is the transmittance. As shown in Figure 3, the absorption is strongest in Nd:YVO4 when the optical electric field is parallel to the crystal C axis, and the absorption is within ±10° from where θ is 00 or 180°. It can be seen that efficient excitation is possible if

Next, FIG. 4 shows the wavelength dependence of the absorption characteristics of a-axis cut Nd:YVO4. FIG. 4(a) shows the case where the crystal C axis and the optical electric field are perpendicular, and FIG. 4(b) shows the case where the crystal C axis and the optical electric field are parallel. Comparing Figure 4 (a) and (b), it can be seen that when the optical electric field is parallel to the crystal C axis, absorption is not only stronger than when it is perpendicular, but also that the wavelength band of strong absorption is wider. . For this reason, it is important to excite the crystal C-axis so that the direction of the photoelectric field is parallel to it, or at least the angle between them is within about 10°.
4 is found to be effective when used in a laser.

Figure 5(b) shows an a-axis cut Nd:YV with a thickness of 3 mm.
O4 is excited from the end face with a semiconductor laser, and wavelength 1
The dependence of the laser output on the excitation wavelength when oscillating a 1064n laser is shown. For comparison, the results when Nd:YAG was used are shown in FIG. 5(a). Nd: YAG
When using Nd:YVO4 with a-axis cut, the laser output changes greatly depending on the wavelength of the semiconductor laser used for excitation, whereas when using a-axis cut Nd:YVO4, the optical electric field of the excitation light becomes parallel to the crystal C-axis. When pumped in this way, the laser output can provide nearly flat characteristics over a wide excitation wavelength range. For these reasons, even in a wavelength conversion laser in which a nonlinear optical crystal for second-order harmonic generation is installed in the resonator, a-axis cut Nd:YVO4 is used, and the optical electric field of the excitation light is parallel to the crystal C-axis. It can be seen that when pumped so that

(Example) The present invention will be described in detail below with reference to the drawings.

FIG. 1 is a perspective view of a first embodiment of the invention. The a-axis cut Nd:YVO4 crystal 4 has a dielectric multilayer thin film mirror 3 attached to the side where the semiconductor laser 1 is located among the two a-axis cut surfaces so that 11064n is 100% reflected. be. Output mirror 5 has 8 for 11064n.
A dielectric multilayer thin film is applied so that the reflectance is about 0 to 98%. Dielectric multilayer thin film mirror 3 and output mirror 5
．． , constitute a laser resonator. By changing the wavelength at which these dielectric multilayer thin films exhibit high reflection, it is also possible to oscillate at wavelengths other than 11064n, such as 946nm and 1340nm. The semiconductor laser 1 has a wavelength of 800 nm to 815 nm, and the optical electric field of the laser beam is parallel to the C axis of the Nd:YVO4 crystal 4. Here, even if the optical electric field and the crystal C axis are not completely parallel, the efficiency hardly changes until the deviation from parallelism is about 10°. The laser beam emitted from the semiconductor laser 1 is focused by the lens 2 and irradiated onto the Nd:YVO4 crystal, thereby exciting the Nd:YVO4 and producing 11064n.
The laser beam is taken from the output mirror 5.

FIG. 2 is a perspective view of a second embodiment of the invention.

The difference from the first embodiment is that a nonlinear optical crystal for wavelength conversion is provided between the Nd:YVO4 crystal 4 and the output mirror 5.
TP (KTiOPO4) crystal 6 is provided. In order to efficiently generate the second harmonic, the output mirror 5
The reflectance of Nd:"'l' is 1 for the oscillation wavelength of VO4.
It is set so that it becomes 00%. Note that in this example, KTP is used as the nonlinear optical crystal for wavelength conversion, but
Nd: BBO (β-BaB204), LBO (LiB4O
7) It goes without saying that nonlinear optical crystals other than KTP, such as LiIO3, are used.

(Effects of the Invention) According to the present invention, the accuracy of wavelength control of a semiconductor laser for exciting a solid-state laser is greatly relaxed, output fluctuation is small, and the range of selection of the semiconductor laser to be used is widened. A laser-pumped solid-state laser can be provided.

[Brief explanation of drawings]

FIG. 1 is a perspective view for explaining the first embodiment of the present invention, FIG. 2 is a perspective view for explaining the second embodiment of the present invention, and FIGS. 3 and 4 are for explaining the present invention. Regarding, Nd:”嘗′04
It shows the absorption characteristics of crystals, and Figure 3 shows Nd:YVO4
Figure 4(a) is a diagram showing the relationship between the angle between the crystal C-axis and the direction of the optical electric field and the absorption characteristics. Figure 4(b)
is a diagram showing the absorption characteristics when the C axis of Nd:YVO4 crystal and the optical electric field are parallel, and Figure 5 (a) is a diagram showing the absorption characteristics when the C axis of Nd:YVO4 crystal and the optical electric field are parallel.
Figure 5(b) shows the dependence of the laser output on the excitation wavelength when the laser is oscillated by the a-axis cut Nd:YV.
FIG. 3 is a diagram showing the excitation wavelength dependence of the laser output when O4 is excited and oscillated so that the electric field of the excitation light is parallel to the crystal C axis. In the figure, 1... Semiconductor laser, 2... Luns, 3... Dielectric multilayer thin film mirror, 4... Nd:YVO4 crystal, 5...
・Output mirror, 6°, KTP crystal

Claims (2)

[Claims] (1) In an end-pumped semiconductor laser pumped solid-state laser, a-axis cut Nd:YVO_4 is used as the solid-state laser crystal.
A semiconductor laser-excited solid-state laser characterized in that the laser is excited using a semiconductor laser for excitation such that the direction of the optical electric field of the excitation semiconductor laser and the crystal c axis of the Nd:YVO_4 are parallel to each other. (2) The semiconductor laser pumped solid-state laser according to claim 1, wherein a second-order nonlinear optical crystal for generating harmonics is provided in a resonator of the solid-state laser.