Yasuharu Koyata

208-W TEM00 operation of a diode-pumped Nd:YAG rod laser.

208-W average-power TEM(00) -mode operation from a diode-pumped Nd:YAG rod laser was demonstrated. The side-pumping method of generating a high-gain aberration-free rod, the bifocusing-compensation technique with two identically pumped rods, and a suitable choice of beam spot size were employed in the design of this laser. At the maximum pump power of 1.1 kW the fundamental transverse-mode operation (M(2)<1.1) was characterized by 7.6% electrical efficiency. The extraction efficiency was almost 60% of full multimode operation. Stable operation was obtained within a pump-power range of 15% of the maximum pump power.

Improved pump-beam distribution in a diode side-pumped solid-state laser with a highly diffuse, cross-axis beam delivery system

A new cavity for diode side-pumped solid-state lasers was designed, built, and tested. The results were efficient absorption of pumped light in the media and homogeneous pumped-beam distribution under various pump-power levels, which generated Nd:YAG active media of different radii and concentrations and shifts of the diode wavelength. Full-multimode quasi-continuous pump operation with a slope efficiency of 40.5% was obtained from a plane-plane resonator equipped with two Nd:YAG rods. At a maximum average pump power of 1.33 kW, the optical-to-optical efficiency was 31.4%. Single-transverse-mode operation (M(2) factor of less than 1.1) of 163 W was demonstrated.

Planar-waveguide quasi-phase-matched second-harmonic-generation device in Y-cut MgO-doped LiNbO3

A planar-waveguide quasi-phase matched second-harmonic generation device, which consists of a Y-cut periodically poled MgO-doped LiNbO3 core and SiO2 claddings, provides 1-W green light with 30-% conversion efficiency at room temperature.

Blue light generation in a ridge waveguide MgO:LiNbO3 crystal pumped by a fiber Bragg grating stabilized laser diode.

We report cw blue light generation by using a periodically poled MgO:LiNbO(3) crystal with a ridge waveguide pumped by a fiber Bragg grating stabilized laser diode with 0.25 nm spectrum width in the coherent collapse regime. Blue light generation of 73 mW with 27% conversion efficiency and a wide temperature tolerance of 5.7 degrees C were attained.

100-W class diode-pumped Nd:YAG MOPA system with a double-stage relay-optics scheme

Abstract We describe a diode-pumped master-oscillator power-amplifier system with two-rod Nd:YAG media and double-stage relay optics scheme. At the repetition rate of 2.4 kHz it delivers an average power of 108 W with Q-switched pulses of 47 ns duration. The laser beam is characterized by an M 2 factor of 2.5×2.7. A model of amplification, which takes into account the temporal overlap between the beams that propagate forwards and backwards in the amplifier stage, was developed to explain the experimental results.

Master-oscillator power-amplifier scheme for efficient green-light generation in a planar MgO:PPLN waveguide

We developed a new master-oscillator power-amplifier scheme consisting of a tapered semiconductor amplifier and a fiber-grating-stabilized laser diode for efficient green-light generation in a planar MgO:PPLN waveguide, and demonstrated cw green-light generation of 346 mW.

Burst-mode Q-switching operation of a Nd:YAG rod laser

High average power (grater than 100 W) with high brightness operation of diode-pumped rod type Nd:YAG laser is investigated. The key technologies to compensate thermal distortions are described and the high brightness operations of normal and Q-switched modes are demonstrated.

Long-time operation of a 100-W green average-power two-rod double-pass Nd:YAG MOPA system

A diode pumped Nd:YAG rod master-oscillator power-amplifier system that delivers 220 W average power in a near top-hat beam distribution has been developed. The repetition rate is 2.5 kHz (25% duty cycle) and the pulse width is approximately 50 ns. With a two-stage KTP crystal 131 W green average power was obtained at frequency-conversion efficiency as high as 65.2%. The system was continuously operated 100 hours starting with an initial green power of 106 W. As the experiments finished the green power was 97.4 W. The decrease in green power, which was mainly attributed to the gray tracing effect in KTP, was characterized by a slope of 0.07-%/hour. The amplifier heads incorporate new concepts for both the pump cavity and the pump source to cavity transport line. Thereby the results of which were an efficient absorption of the pumped light in the media and homogeneous pumped-beam distribution under various pump-power levels, Nd:YAG active media of different radii and concentration and shifts of the diode wavelength resulted.

63.5L: Late‐News Paper: Planar‐Waveguide Green Laser for Laser TV

We have newly developed an ultra-compact, highly efficient and high-power green laser for a light source of laser TV. A planar-waveguide configuration improves performance of solid-state green laser dramatically. The laser consists of essential minimum three devices (a pump LD, a planar-waveguide Nd:YVO4 and a planar-waveguide PPMgLN). Output green peak power of 11.4-W with the corresponding electrical efficiency of 21% is demonstrated. In addition, temperature insensitive features are also proved. The size of developed laser module is as small as 5cc. We believe this laser is the most suitable green laser light source for laser TV at present.

High-average power Q-switched operation of a Nd:YAG rod laser

Summary form only given. Ranging from fundamental physics to the engineering field, high-power diode-pumped solid-state lasers are attractive light sources for various applications. In particular Q-switched operation, used to generate high peak power IR output or green output, is important for material processing, energy applications and environment measurements. It is known that efficient-operation in the Q-switched regime requires a repetition rate higher than the inverse of the medium spontaneous fluorescence lifetime. But in the condition of continuously pumping with fixed power, the pulse duration increases and the pulse peak-power decreases. A way to shorten the pulse duration is to shorten the resonator length as much as possible. This solution is suitable for miniature lasers, but very difficult to fulfil in a high-power system, because intracavity optical elements must be used, as example to optimize the laser-beam spot-size or to compensate for thermal aberration induced by pumping. Another way to shorten the pulse duration is to increase the pump power and increase the gain in the active medium. Our approach to these problems is a quasi-continuous pumping regime which increases gain in the active medium under the fixed condition of thermal effects. We report our results on a high-average power Q-switched Nd:YAG rod laser which is quasi-continuous pumped.