Nd:YVO and YVO laser crystal integration by a direct bonding technique

Sugiyama, Akira; Fukuyama, Hiroyasu; Katsumata, Masaki*; Okada, Yukikatsu*

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.