Reduction of Amplitude-to-Phase Conversion in Charge-Compensated Modified Unitraveling Carrier Photodiodes

The amplitude-to-phase (AM-to-PM) conversion in photodetectors is one the primary noise sources in the generation of ultralow noise microwave signals with stabilized optical frequency combs. We have designed charge-compensated modified unitraveling carrier (CC-MUTC) photodiodes to reduce the AM-to-PM conversion. The photocurrent-induced phase change at 15 GHz is reduced by >3 times and the AM-to-PM is greatly suppressed, especially at large photocurrent. For 10-μm devices, the 3-dB bandwidth at -6 V is 35 GHz and the maximum RF output power is 13.7 dBm at 15 GHz. Compared with the original CC-MUTC structure, the maximum output power is increased by 2.7 dB.