Optoelectronic Hybrid Concept for Widely Tunable, Frequency- and Phase-Locked Continuous-Wave Optical Terahertz Beat Signals by Four-Wave Mixing

Highly stabilized terahertz frequency signals are required in VNA concepts, e.g., for the precise frequency characterization of devices for future 6G communication applications. In this contribution, we present the extension of a recently demonstrated, optoelectronic hybrid locking scheme for the generation of widely tunable phase-locked laser beat signals in the terahertz range by a four-wave mixing approach. We use an optical phase-locked loop (OPLL) to stabilize the difference frequency of two continuous-wave lasers. The laser signals are amplified in tapered semiconductor optical amplifiers (SOAs) to induce four-wave mixing contributions. By selecting the optical signal frequencies in a filter setup, we obtain a wide range of frequency-locked beat signals which can be further employed for the optoelectronic generation and detection of highly stabilized terahertz photomixing signals.