Efficient RF Frequency Down-Conversion Using Coupled Quantum-Well Optical Phase Modulator

Frequency down-conversion is important to radar front-end. In this work, we achieve efficient RF frequency down-conversion using a coupled quantum-well optical phase modulator fabricated on an indium phosphide material platform. When used in conjunction with an optical phase-locked loop-based linear phase demodulator, a 1-mm-long device exhibits a down-conversion loss of ~2.6 dB and a spurious-free dynamic range of ~125 dB·Hz^2/3 in the photodetector shot-noise limit. Furthermore, the phase modulator has a very low optical propagation loss (<;0.2 dB/mm). This allows for a longer modulator device capable of achieving even higher performance.