JP2586200B2 - Macro chip solid-state laser device - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a semiconductor laser-excited solid-state laser device.

(Prior art) A microchip solid-state laser in which a semiconductor laser diode for excitation and a solid-state oscillating element are adhered to each other is ultra-small, has a long service life, can easily perform single transverse mode and single longitudinal mode oscillation, and has a high frequency modulation. It has many advantages such as being possible.
Recently, laser research on microchip lasers has been actively pursued because high-output lasers with an output of 1 watt or more have been put into practical use as laser diodes for excitation. A semiconductor laser with an output of several tens of milliwatts or more in an oscillation wavelength of 800 nm is usually used for the excitation laser, and Nd: YAG is used for the solid-state oscillation device.
(Yttrium aluminum garnet with neodymium,
Nd: Y ₃ Al ₅ O ₁₂ ) single crystals have been used.

(Problems to be Solved by the Invention) In a semiconductor laser pumped solid-state laser, the output of the semiconductor laser must be efficiently absorbed by the solid-state oscillation element. Currently, the oscillation wavelength of the semiconductor laser that provides the highest output is in the 800 nm band, but since Nd ³⁺ absorption is near this, oxide crystals doped with Nd as the active band are widely used as solid-state oscillation devices. I have. Among them, Nd: YAG crystals, which are most widely used as solid-state laser materials, are generally used. By the way, a microchip laser is required to be as thin as possible as an oscillating element in order to sufficiently exhibit its features, and for that purpose, a material having good excitation light absorption efficiency is desired. For Nd: YAG crystal,
Since the Nd concentration in the crystal is usually 1.5 at% or less from the two aspects that the optical uniformity of the grown crystal and the concentration quenching, that is, the fluorescence lifetime is reduced by the mutual interference of Nd-Nd atoms, the Nd concentration is There is a limit in increasing the pump light absorption efficiency. Further, there is a drawback that a single longitudinal mode cannot be easily obtained when converting into a second harmonic green laser light by a non-linear optical element of Nd: YAG laser light.

SUMMARY OF THE INVENTION The present invention has been made to improve the absorption efficiency of excitation light, improve the performance of a microchip laser, and obtain a second harmonic having a high beam quality.

(Means for Solving the Problems) In the present invention, the problems of conventional materials such as Nd: YAG can be achieved by using a single crystal of YVO ₄ (yttrium vanadate) doped with a rare earth element such as Nd as a solid-state laser oscillation element. Was solved.

(Action) The present inventors grew a single crystal of Nd: YVO ₄ containing 1.1 at% of Nd and a single crystal of Nd: YAG also containing 1.1 at% of Nd for comparison. A sample for absorption measurement was prepared, and the light absorption at a wavelength of 809 nm was measured. Nd: YA
The absorption coefficient of G was 6.0 cm ⁻¹ , whereas Nd: YVO ₄ was anisotropic, 9.2 cm ^{−1 in the} c-axis direction, and 31.1 c in the a-axis direction.
m ^-1 . This result, Nd as a microchip laser: a shaft cut plate of YVO ₄ has been found to be excellent. Furthermore, the second harmonic (532 nm, one half of 1064 nm of oscillation light) could be obtained stably by using Nd: YVO ₄ as an oscillation element and using a nonlinear optical element KTP (KTiOPO ₄ ) as an internal resonance type. Nd: in the case of YAG is for stable oscillation, it is necessary to use a quarter-wave plate but, Nd: YVO not in need thereof _4. This is related to the fact that YVO ₄ is a uniaxial crystal and the output laser light is polarized.

(Embodiment) FIG. 1 shows an embodiment of the present invention. 1 is a semiconductor laser diode chip for excitation, maximum output 1W, oscillation wavelength 809n
m (20 ° C), 2 is a Nd: YVO ₄ oscillation element, the Nd concentration is 1.1at%,
The thickness is 1.0 mm. The excitation light incident surface of the oscillation element,
A non-reflection coating for excitation light and a total reflection code for oscillation light (1064 nm) are applied to the contact surface with the laser diode on the left end. The output side was a mirror surface with a reflectivity of 95%. In this configuration, when the output of the semiconductor laser for excitation was gradually increased, oscillation of 1064 nm was confirmed at 50 mW. FIG. 2 shows an application example of the present invention to which a non-linear optical element is added. Reference numeral 3 denotes a 7 mm thick KTP element for generating a second harmonic. The left end of the 1 YVO ₄ oscillation element and the right end of the 3 KTP nonlinear element constitute a resonator for 1064 nm. That is, on the input side of 1, there is a non-reflection coating for the excitation light of 809 nm, and on the input side of 3, a total reflection film of 1064 nm for forming a resonator of Nd: YVO ₄ oscillation.
nm total reflection film and a non-reflection coating for the second harmonic 532 nm. In this configuration, green light was observed when the output of the laser diode was about 200 mW or more. N
Comparison of laser oscillation output for the same input between the case of using d: YAG and the case of using Nd: YVO ₄
The value of d: YVO ₄ was about four times that of Nd: YAG in the fundamental oscillation, and about ten times that of Nd: YAG in the second harmonic output. As for the second harmonic, single longitudinal and transverse modes were obtained.

(Effects of the Invention) According to the present invention, it is possible to obtain an ultra-small, highly efficient, and stable solid-state laser device. In the present invention,
Nd and activate Nd: Although only described YVO _4, microchip lasers by suitably selecting the oscillation wavelength of the pumping semiconductor laser was a YVO ₄ that an active substance other rare earth elements and oscillating element Of course, it is also possible. Furthermore, a practical device can be developed by adding a modulation element, a Q switch element, and the like.

[Brief description of the drawings]

1 and 2 are views showing an embodiment of the present invention. 1. indicates a semiconductor laser diode chip, 2. indicates an Nd: YVO ₄ oscillation element, 3. indicates an element for KTP.SHG, and 4. indicates a mount.

 ────────────────────────────────────────────────── ─── Continued on the front page (72) Inventor Sadao Nakai 3-6-45 Kita Kasugaoka, Ibaraki City, Osaka Prefecture

Claims (3)

(57) [Claims] 1. A and pumping semiconductor laser diode, a microchip solid-state laser device being characterized in that arranged a YVO ₄ single crystal obtained by adding neodymium brought into close contact with the laser oscillation element according to the material. Wherein the pumping semiconductor laser diode, a microchip solid, wherein a laser oscillation element according to the material of YVO ₄ single crystal with added rare earth element, that was placed in close contact with the wavelength conversion element Laser equipment. 3. A microchip solid-state laser according to claim 1 or 2, further comprising a light modulating element, a light polarizing element,
A microchip solid-state laser device that combines elements driven by external energy such as ultrasonic Q-switch elements.