Ion implanted and epitaxially grown crystal waveguide lasers

Abstract

This thesis reports the results of investigations into laser action in optical waveguides formed by the methods of helium ion implantation and liquid phase epitaxial growth.

Helium ion implantation has been used to produce waveguides in a range of dielectric materials. Of these Nd:GGG and Yb:YAG have been operated as planar waveguide lasers. The most important part of the work on ion implantation has been the fabrication of channel waveguides using a gold stopping mask to prevent ion damage in certain regions. Using this method channel waveguide lasers have been produced in Nd:YAG, Nd:GGG and Nd:MgO:LiNbO3. These have all shown low threshold operation with the Nd:YAG channels lasing with an absorbed power threshold of 540µW when diode pumped. The second method used to fabricate waveguides was that. of liquid phase epitaxial growth. This has produced doped YAG waveguides of extremely high optical quality and with very low propagation losses (typically 0.1 dB/cm). End pumped experiments on planar Nd:YAG waveguides have produced lasers with absorbed power thresholds as low as 670µW. As well as the 1.06µm transition laser action in Nd:YAG guides has also been obtained at 1.32µm and 946nm. Laser action has been demonstrated in a diode-array side-pumped configuration where the pump and signal light propagate perpendicular to each other. Yb:YAG waveguides have lased on the quasi-three-level transitions at 1.03 and 1.05µm. Because of the strong reabsorption losses present in this laser system the effect of any waveguide propagation loss becomes negligible and the resulting laser performance is excellent. When diode pumped at 968nm the laser threshold was 43mW and the slope efficiency 77%.

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