High performance evanescent edge coupled waveguide unitraveling-carrier photodiodes for >40-gb/s optical receivers

We have demonstrated a low-cost high-bandwidth and high-responsivity evanescent waveguide unitravelling-carrier photodiode (PD) fabricated using all 2-in InP processing including on-wafer mirrors and coating. Optimization of the optical input waveguide was made using the method of the genetic algorithm associated with a beam propagation method. Optical fiber coupling to the PD is based on a diluted multimode waveguide allowing simple material epitaxial growth. The fabricated PDs exhibit simultaneously 0.76-A/W responsivity at 1.55 μm, >50-GHz bandwidth, and more than 22-mA average saturation photocurrent at 50 GHz. The light polarization dependence is less than 0.1 dB.