Low-Loss Waveguides by Planar Modified Chemical Vapor Deposition

We present a novel method to fabricate planar photonic devices for high power applications using modified chemical vapor deposition (MCVD) technology. The MCVD process, usually applied to optic fibers, is used here to deposit a layer of Ge doped silica on a fused silica slab. The doped layer was then heat-treated by a CO2 laser in order to achieve high optical quality and increase its damage threshold. Finally, direct laser lithography, followed by deep dry etching, was used to shape straight and curved large-core air-cladded waveguides with smooth sidewalls. The straight waveguides were shown to have an excellent propagation loss, 0.33 dB/cm, and the curved waveguide had a propagation loss of 1 dB/cm.