Compact mode expanded lasers using resonant coupling between a 1.55-μm InGaAsP tapered active region and an underlying coupling waveguide

We demonstrate a novel expanded mode laser for enhanced laser-fiber coupling based on resonant coupling between a tapered active waveguide and an underlying coupling waveguide. This device was grown in a single standard epitaxial growth and was processed using conventional fabrication techniques, thus making it attractive for low-cost manufacturing. The total taper length required for mode transformation was 200 mu m and the excess mode transformation loss was 0.6 dB indicating the compact, low-loss mode transformation. Far-field divergence angles (13 degrees x 24 degrees) and improved coupling to cleaved single-mode fibers (3.8-dB coupling loss) were achieved.