Recent Advances and Future Prospects in High-Speed and High- Saturation-Current Photodetectors

High power photodetectors have a made remarkable progress in performance over the last few years with prospective application in high-bit-rate digital receivers with reduced complexity, CATV, analog-to-digital converter, high power RF distribution and optoelectronic generation of high power microwaves and millimeter-waves in RF photonic systems. An in depth understanding of the failure mechanism and novel techniques in thermal management have dramatically improved the power handling capability of the high power photodiodes. In order to increase the output RF power of the photodiodes, several groups have developed surface-illuminated, waveguide, traveling-wave, unitravelling carrier, parallel fed traveling wave with MMI couples and distributed photodetector arrays. An impressive improvement in link gain, noise figure, and spurious free dynamic range (SFDR) of externally modulated links has been achieved by several groups. The realization of high power balanced photodetectors has helped suppress the relative intensity noise (RIN) of the laser source and the amplified spontaneous emission noise (ASE) from erbiumdoped fiber amplifiers (EDFA) reaching the level of quantum noise floor. This paper will briefly discuss various approaches that different research groups have undertaken and will discuss our recent advances in power handling capability and reliability analysis of velocity-matched distributed photodetectors (VMDP) and balanced photodetectors for RF photonic links.