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Sugiyama, Akira; Nara, Yasunaga
JAERI-Research 2003-023, 14 Pages, 2003/11
We succeeded in fabrication of an integrated laser crystal with good heat conductivity by bonding two kinds of crystals; one is neodymium-doped YVO crystal (Nd: YVO) which is used for high peak power lasers and another is its host crystal YVO. Instead of conventional chemical etching, dry etching technique using an argon ion beam has been newly developed for the bonding of these crystals. It is essential for the heat treatment of this bonding to optimize the processing temperature for preventing vanadic acid precipitation due to thermo-chemical reaction. Optical characteristics of the bonded crystals were investigated. Bonded interface of the crystal was also observed with a transmission electron microscope (TEM). Through this experimental study, we made it clear that thermal conductivity of the integrated Nd: YVO/YVO crystal is much improved and the crystal possesses good lasing capability of increasing laser output without destruction of crystals due to thermal stress.
Sugiyama, Akira; Fukuyama, Hiroyasu; Katsumata, Masaki*; Okada, Yukikatsu*
Integrated Optical Devices: Fabrication and Testing (Proceedings of SPIE Vol.4944), p.361 - 368, 2003/00
We report recent progress in bonding of crystals used in microchip lasers, Nd:YVO and non-doped YVO crystal that functions as a cold finger. The bonding technique consists of a dry etching process for polished crystal surfaces to be bonded and a successive transformation from hydrogen bonding to oxygen-bridged bonding at temperature below half of the melting point of crystal. Roughness of the surfaces was less than 0.2-lambda at 633 nm. After the etching of around 30 nm by an argon ion beam, the surfaces were contacted in the clean ambient, then heat treatment was done for 50 hours in a vacuum furnace. To evaluate the bonded region, we made optical scattering measurements, and laser oscillation tests pumped by a laser diode with the output power of 20 W. From these experiments, it was clear that the number of defects on the bonded surface is much smaller than that of the intrinsic defects, and the integrated crystal, improving thermal conductivity, can produce twice of laser output power compared with a usual one.