Sunao Kurimura

Microchip high-power radially pumped composite Yb:YAG laser

A novel design for a quasi-three level, microchip high-power laser is proposed. The design uses a Yb:YAG core surrounded by an undoped YAG region of slab shape that could be pumped from one or from both slab sides. Theoretical descriptions of the pumping optimization, pump-beam distribution, and output-to-input power characteristics are presented. The simulations show that from a composite Yb:YAG chip, which consists of a Yb:YAG core of 2.0-mm diameter and 13.0-at.% Yb concentration surrounded by an undoped YAG slab of 5.0-mm width and 0.8-mm thickness, a TEM00 output beam of 100 W continuous-wave power could be obtained. The expected optical-to-optical efficiency is 39%.

Optical absorption and emission spectroscopy of Nd:Bi4Si3O12 grown by Bridgeman method

Up to 5.0 at.% Nd3+ doped Bi4Si3O12 single crystals were realized by the Bridgman method. The spectroscopic parameters were evaluated and found that Nd3+:Bi4Si3O12 has a large quenching parameter (3.6 at.%) and very wide bandwidth in both transition of emission (23.1 nm) and absorption (16.1 nm). These properties are suitable for diode- pumped solid state lasers.

Periodical poling characteristics of 5mol% MgO-doped congruent LiNbO 3 crystals at elevated temperature

A large cross-section quasi-phase-matched device using 5 mol% MgO-doped LiNbO3 (MgO:LN) crystal for high-power wavelength conversion was realized. We have found that the coercive field to invert polarization of the crystal reduces drastically with elevated temperature. The coercive field reduces to 1.2 kV/mm at 250°C, which is about 1/4 compared with that for MgO:LN at room temperature (RT) and about 1/17 of that for LN at RT. 3mm-thick periodically poled MgO:LN has been successfully fabricated with 30 µm period.

Design Criteria for Optimization of Fiber-Coupled Diode Longitudinally-Pumped Lasers Using Pump-Beam M2 Factor

For optimization of longitudinally-pumped solid-state lasers, a model which consider the pump-beam propagation described by its M2 factor is proposed. Analytical functions for the optimum focusing-position, the optimum pump spot-size, the minimum threshold pump power and the maximum overlap efficiency are given. A simple output to input power relation and previous formulae provides a straightforward procedure to design the optimum laser resonator, the coupling-optics and to evaluate the laser output power. A slope efficiency of 57% with a 53% optical-efficiency at maximum 8-W pump-power was obtained from a fiber-coupled longitudinally-pumped Nd:YAG medium. A very good agreement between experiments and theory was obtained.