INP-BASED MULTIPLE-QUANTUM-WELL LASERS WITH AN INTEGRATED TAPERED BEAM EXPANDER WAVE-GUIDE

We demonstrate the integration of a laterally tapered adiabatic mode expander waveguide inside the cavity of diode lasers operating at 1.3 and 1.55 mu m wavelengths. This integration results in narrow output beam divergence with FWHM of 7 degrees and 5 degrees vertically and laterally respectively, The loss caused by the passive waveguide is minor and for devices operating at 1.55 (1.3) mu m threshold currents as low as 12 (22) mA and quantum efficiencies as high as 52% (51%) are obtained, Coupling to a cleaved optical fiber yields broad alignment tolerance with 1 dB excess loss for misalignment of +/-2.6 mu m vertically and +/-3.1 mu m laterally, with a minimum coupling loss of -3.5 dB.