New developments in high speed photodetectors

A progress on the recent developments in high-speed photodetector technology is presented. Different approaches that trigger changes in photodetector structures are also discussed. These include transition from 10 GB/s to 40 GB/s fiber optic systems, the incorporation of normal-incidence input coupling to photodiodes, and the implementation of waveguide photodiodes for very high-speed operation. However, these approaches give rise to certain tradeoffs between bandwidth and responsivity and limitation issues like input coupling efficiency and sensitivity to polarization. Further improvements in device performance and functionality can be anticipated through monolithic integration. Examples include integration of photodiode with a semiconductor optical amplifier or combining detectors in a balanced receiver.