Ultrafast, high-power waveguide fed photodetector with integrated spot size converter

The monolithic integration of an ultrafast photodetector with an spot size transformer is presented. Using a shifting mask technique optimized taper ramp profiles are fabricated. The integrated devices exhibit a more than doubled responsivity (0.7 A/W) and about one magnitude higher misalignment tolerances compared to devices without spot size converters. The ultra large bandwith (f3dB>50 GHz) and the excellent high power behaviour is unimpaired by the integration of the spot size converter.