JP2666548B2 - Semiconductor laser pumped solid-state laser device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ultra-compact semiconductor laser-excited solid-state laser device used for recording and reproduction of an optical disk, a laser printer, or laser applied measurement.

Conventional technology Conventionally, an arc lamp or flash lamp has been used to excite a solid-state laser medium.However, since the pumping efficiency is not good, the efficiency of the entire laser is low, and the radiation of the lamp and the laser medium is reduced. , The neglected had to be large. However, in recent years, as the output of semiconductor lasers has increased,
Attempts have been made to use semiconductor lasers as excitation light sources for solid-state lasers. When a semiconductor laser is used, the wavelength can be adjusted to the absorption band of the solid-state laser,
The excitation efficiency is very good. In addition, since there is no heat generated by absorption of an extra spectrum, heat radiation is also facilitated, and a compact and high-efficiency solid state laser can be realized.

On the other hand, using a nonlinear optical crystal such as a KTiOPO ₄ (KTP) crystal, the infrared light generated by solid-state laser light is converted into harmonics,
A method for obtaining a green or blue visible light laser has been conventionally known, and attempts have been made to utilize harmonics of solid-state laser light excited by the above-described semiconductor laser.

FIG. 4 is a partially cutaway view of a conventional semiconductor laser pumped Nd: YAG laser. This is a solid-state laser medium rod containing Nd in a YAG crystal in the same package (hereinafter referred to as Nd: YAG
8) KTP crystal 9 as non-linear optical crystal, Brewster plate for converting substrate wave in resonator to linearly polarized light
10. A structure in which a selfoc lens 3 for condensing excitation light and a semiconductor laser chip 4 serving as an excitation light source are housed. The resonator of the Nd: YAG laser is formed between the excitation end face 8A of the YAG rod 8 and the emission end face 9B of the KTP crystal 9, and the KTP crystal 9 and the Brewster plate 10
Has been inserted. The fundamental wave is linearly polarized by the Brewster plate 10 to stabilize the output.
The semiconductor laser light is focused on the end face 8A of the Nd: YAG rod 8 by the selfoc lens 3, and excites the Nd: YAG rod 8 in the axial direction. The KTP crystal 9 converts a fundamental wave having a wavelength of 1.06 μm into a second harmonic having a wavelength of 0.53 μm and outputs green light.

In a system in which the Brewster plate 10 is inserted into a fundamental wave resonator as shown in FIG. 4 to make it linearly polarized light, the number of components increases and the length of the resonator becomes longer. The conversion was inconvenient. In addition, the adjustment of the optical axis becomes complicated during assembly, which is a problem.

Means for Solving the Problems In a semiconductor laser-excited solid-state laser device according to the present invention, a nonlinear optical crystal and a solid-state laser medium are arranged on an optical axis so as to be adjacent to each other, and the nonlinear optical crystal and the solid-state laser medium are inwardly directed to each other. And a semiconductor laser for exciting a solid-state laser medium on the optical axis, wherein at least one of the two end faces is a Brewster cut face, and the two end faces facing each other constitute a laser resonator end face. It has a lens for collecting the light emitted from the laser.

According to the present invention, the Brewster cut surface provided on at least one of the nonlinear optical crystal and the solid-state laser medium can transmit only light having polarization and wavelength satisfying the Brewster condition. Linearly polarized light having one wavelength can be selected.

Embodiment Hereinafter, an embodiment of the present invention will be described with reference to the drawings. FIG. 1 shows a partially cutaway view of a semiconductor laser pumped solid-state laser device of the present invention. This structure is based on KTP crystal 2, Nd having a Brewster cut surface in the same package 7,
A YAG rod 1, a selfoc lens 3, and a semiconductor laser chip 4 are sequentially housed. In a manufacturing method for obtaining this structure, a semiconductor chip 4 is attached to a stem fixed to a base 6, and a package 7 on a cylinder containing a KTP crystal 2, an Nd: YAG rod 1, and a selfoc lens 3 is attached to the base 6. It is a thing. 5 is for adjusting the output.
It is a PIN photodiode. The Nd: YAG rod 1 has a Nd concentration of 1.1% in YAG, a diameter of 3 mm, a central axis length of 5 mm, a Brewster cut surface 1B, and a Brewster angle of 61.2 degrees (the refractive index of the Nd: YAG rod is 1.82), and the KTP crystal 2 has a width of 3 mm on one side and a length of 5 m on the axis center.
m, Brewster cut surface 2A, Brewster angle 6
It has a prism shape of 0.4 degrees (KTP has a refractive index of 1.76) and is housed in a holder. FIG. 2 (a) shows Nd: Y of FIG.
The arrangement relationship between the AG rod 1 and the KTP crystal 2 is shown. The length including the main body, that is, the base 6 and the package 7 is 25 mm. In the structure in which the conventional Brewster plate was inserted (FIG. 4), the length was 35 mm, so that it could be shortened by about 10 mm.

Semiconductor laser chip 4 with oscillation wavelength 0.809μm for pumping
The light is focused on the YAG rod 1A by the selfoc lens 3 and axially excited. The resonator is formed between the excitation end face 1A of the Nd: YAG rod 1 and the emission end face 2B of the KTP crystal 2. The excitation end face 1A is a convex mirror having a radius of curvature of 100 mm, and the emission end face 2B is a flat mirror. Has become. KTP crystal 2 is YAG
The structure is such that it is inserted into the laser cavity. Nd: Y
Each surface of the AG rod 1 and KTP crystal 2 has a fundamental wave of 1.06 YAG laser.
μm, a second harmonic of 0.53 μm, and an excitation wave of 0.809 μm, as shown in Table 1. As can be seen from Table 1, only the 0.53 μm green light, which is the second harmonic, is emitted from the emission-side end face 2B of the KTP crystal 2.

FIG. 3 shows the input / output characteristics of the present invention. When the driving current of the semiconductor laser was 500 mA, green light was obtained as second harmonic light (0.53 μm) having a maximum light output of 10 mW. At this time, RIN (R
elative Intensity Noise) was -145 dB / Hz.

In the present embodiment, the Brewster cut surface is provided on the end faces of the Nd: YAG rod 1 and the KTP crystal 2, but it is sufficient to provide the Brewster cut surface on only one of them.
FIGS. 2 (b) and 2 (c) show arrangement diagrams in the case where the cut surface is provided only on the Nd: YAG rod and in the case where the cut surface is provided only on the KTP crystal.

Effects of the Invention As is apparent from the above description, according to the present invention, the nonlinear optical crystal and the solid-state laser medium are arranged adjacent to each other on the optical axis, and the nonlinear optical crystal and the solid-state laser medium face each other. At least one of the two end surfaces is a Brewster cut surface, and the two outwardly facing end surfaces constitute a laser cavity end surface. The semiconductor laser for exciting a solid-state laser medium and the light emitted from the semiconductor laser are arranged on the optical axis. By configuring a semiconductor laser-pumped solid-state laser device having a lens for condensing the light to be emitted, the output of the second harmonic is stabilized, and noise can be reduced. As a result, a great effect is exhibited by using it as an ultra-small green laser with a low nozzle output for recording and reproduction of optical disks, laser printers, laser applied measurement, and the like.

[Brief description of the drawings]

FIG. 1 is a partially broken cross-sectional view of a semiconductor laser pumped solid-state laser device according to the present invention, and FIG. 2 (a) illustrates an arrangement of an Nd: YAG rod having a Brewster cut end face and a KTP crystal included in FIG. FIG. 2 (b) is a view for explaining an arrangement in which only a Nd: YAG rod has a Brewster cut surface, FIG.
FIG. 3 (c) is a diagram for explaining an arrangement in the case where only a KTP crystal has a Brewster cut surface, FIG. 3 is a diagram showing a harmonic output with respect to a drive current of a semiconductor laser pumped solid-state laser device of the present invention, and FIG. It is a structural diagram of a conventional semiconductor laser pumped solid-state laser device. 1 ... Nd: YAG rod having Brewster cut end face,
2 ... KTP crystal with Brewster cut end face, 3 ...
... Selfoc lens, 4 ... Semiconductor laser chip, 5
… PIN photodiode, 6… Base, 7… Package, 8… Nd: YAG rod, 9… KTP crystal, 10…
Brewster board.

Claims (2)

(57) [Claims] 1. A nonlinear optical crystal and a solid-state laser medium are arranged adjacent to each other on an optical axis, and at least one of two end faces of the nonlinear optical crystal and the solid-state laser medium facing each other is inward. A Brewster cut surface, and two outwardly facing end surfaces constitute a laser cavity end surface;
And a semiconductor laser for exciting the solid-state laser medium and a lens for condensing light emitted from the semiconductor laser on the optical axis. 2. The semiconductor laser-excited solid-state laser device according to claim 1, wherein said semiconductor laser, said lens, said solid-state laser medium, and said nonlinear optical crystal are housed in the same package.