Abstract :
An integrated optical mode expander is reported which reduces measured coupling losses between high-NA rib-loaded GaAs/AlGaAs waveguides and standard fibre to 3 dB at 1.3 μm wavelength. By adding a low refractive index buffer layer to an existing waveguide geometry, and laterally tapering a new etched rib of carefully selected depth, an adiabatic and reciprocal `drive-down´ transition to a large spot-size mode is achieved. The wet-etched device does not require semiconductor regrowth or submicrometre patterned features
Keywords :
III-V semiconductors; aluminium compounds; gallium arsenide; integrated optics; optical couplers; optical fabrication; optical fibre couplers; optical loss measurement; optical waveguides; refractive index; rib waveguides; semiconductor growth; 1.3 mum; GaAs-AlGaAs; GaAs/AlGaAs rib waveguides; buffer layer; coupling loss measurement; drive-down; drive-down technique; etched rib; existing waveguide geometry; high-NA rib-loaded GaAs/AlGaAs waveguides; improved fibre coupling; integrated optical mode expander; large spot-size mode; laterally tapering; low refractive index; regrowth-free mode; selected depth; wet-etched device;
