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and YVO single crystalSugiyama, Akira; Nara, Yasunaga; Wada, Kengo*; Fukuyama, Hiroyasu
Journal of Materials Science; Materials in Electronics, 15(9), p.607 - 612, 2004/09
Laser crystal bonding of a neodymium-doped yttrium orthovanadate (Nd: YVO) and a non-doped yttrium orthovanadate (YVO) crystal as a cold finger has been demonstrated. Instead of a traditional chemical treatment, a newly developed dry etching process was applied to the preparation for contact of mechanically polished surfaces. In the subsequent heat treatment process, stable heating at 873 K was required to prevent precipitation at the bonded interface. The bonded interface of 3 mm 
3 mm was investigated by optical scattering and wavefront distortion measurements. The scattering density around the bonded interface was less than 4.610
/cm
and the wavefront distortion caused by the bonded region was assumed to be around 0.04-wave at 633 nm. Additional magnified inspection showed that atoms in the bonded region were well arranged with the same regularity as the bulk crystal. The diffusion coefficient of Nd
ions in the YVO crystal was estimated at 2.310
m
/sec at 873 K.
yttrium orthovanadate bonded laser crystalsSugiyama, Akira; Nara, Yasunaga
JAERI-Research 2003-023, 14 Pages, 2003/11
JAERI-Research-2003-023.pdf:2.09MB
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.
and YVO laser crystal integration by a direct bonding techniqueSugiyama, 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.