COMPACT MODE EXPANDERS USING RESONANT COUPLING BETWEEN A TAPERED ACTIVE-REGION AND AN UNDERLYING COUPLING WAVE-GUIDE

A novel technique for enhanced laser-fiber coupling, based on resonant power coupling between a tapered active waveguide and an underlying c oupling waveguide, is presented, Spot-sizes are transformed from 2.0 x 1.1 mu m in the active region to 6.0 x 3.1 mu m in the coupling waveg uide, over a length of 200 mu m, with a mode transformation loss of on ly 0.36 dB, Butt-coupling efficiencies of 55% (2.6 dB loss) are estima ted to standard cleaved single-mode fibers at 1.55 mu m. The proposed device requires a single epitaxial growth and conventional processing techniques, making it amenable for low-cost manufacturing.