252-GHz Compact All-Electronic CMOS Optopair with SNR of 62 dB

A free space 252 GHz quasi-optical emitter-detector pair (optopair) is implemented in standard Si CMOS technology. The THz source consists of a voltage-controlled differential field-effect-transistor (FET) based Colpitts oscillator emitting at the third harmonic with total radiated power -11.1 dBm and 35 mW DC power consumption. The detector is a resonant-antenna-coupled FET-based power detector for quasi-optic coupling through the substrate lens. The detector exhibits a minimum optical noise equivalent power as low as $22{\text{pW}}/\sqrt {{\text{Hz}}} $ at 252 GHz. The system reveals 61.7 dB power signal to noise for 1 Hz equivalent noise bandwidth in the direct detection regime. The practical application of the pair for two-dimensional imaging is also demonstrated.