Fabrication of microlenses in compound semiconductors and monolithic integration with diode lasers

Large-numerical-aperture microlenses have been fabricated in compound semiconductors by chemical etching and mass transport (surface-energy minimization) and have been monolithically integrated with GaInAsP/InP surface-emitting lasers. The microlenses showed smooth surface, accurate profiles, and near diffraction-limited beam collimation. Techniques have been developed for accurate alignment between microlenses and buried-heterostructure waveguide gain regions fabricated on opposite sides of a substrate. The integrated devices showed room-temperature pulsed threshold currents of 70 mA, narrow beam divergence of 1.25 deg, and are potentially advantageous for fiber coupling, optical interconnects, laser-array applications, etc.