Fluoride glass planar waveguides for active applications

To help develop an efficient planar optical amplifier, the single mode behaviour of large cross-section rib optical waveguide structures (15 μm high and up to 19 μm wide) made of fluoride glasses have been investigated numerically. Wet chemical etching offers a simple and cheap solution for the fabrication of rib patterns in fluoride glasses, we present measurement of the lateral rib roughness left by this process as well as calculation of consequent scattering losses. We show that such large cross-section rib waveguides show a better tolerance to the rib roughness than standard semiconductor waveguides. This is of practical importance in order to make use of the full benefit of the amplification.