InP-based multiple quantum well lasers with an integrated tapered beam expander waveguide

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 μm wavelengths. This integration results in narrow output beam divergence with FWHM of 70 and 50 vertically and laterally respectively. The loss caused by the passive waveguide is minor and for devices operating at 1.55 (1.3) μm 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 /spl plusmn/2.6 μm vertically and /spl plusmn/3.1 μm laterally, with a minimum coupling loss of -3.5 dB.