Optoelectronic Feedback Loop for Phase Noise Suppression in THz Self-Heterodyne Detection

A novel terahertz (THz) self-heterodyne detection system using an optoelectronic feedback loop is proposed. Conventional THz self-heterodyne detection system is inherently vulnerable to phase noise associated with the optical path length difference between the laser sources and the photomixer. The proposed THz self-heterodyne detection system utilizes the optoelectronic feedback loop to suppress the phase noise of the intermediate frequency signal at the output of the photomixer. The optoelectronic feedback loop requires a feedback loop with a relatively small loop bandwidth and thus is implemented without using rather sophisticated integrated photonics technology. The proposed THz self-heterodyne detection system with the optoelectronic feedback loop suppresses the phase noise by more than 25 dB.