Fully Integrated Photonic Millimeter-Wave Tracking Generators on the Heterogeneous III–V/Si Platform

Fully integrated photonic microwave/millimeter-wave (MMW) tracking generators, which include wavelength-tunable lasers, distributed feedback lasers, phase modulators, and high-speed photodiodes (PDs), are demonstrated on the heterogeneous integrated III-V-on-Si photonic platform. Two on-chip lasers are locked by an external optical phase-locked loop (OPLL), and the two-tone radio-frequency (RF) signals from the on-chip fast PDs can be photonically generated through the heterodyne-beating process between the wavelength-tunable laser and the OPLL output. Furthermore, the frequency spacing between such two-tone RF signals can be tracked by the oscillation frequency in the OPLL with a wide tunability (near dc to 10 GHz). Fast and truly continuous scanning of photo-generated MMW signals thus becomes feasible by simultaneously tuning the OPLL and the central wavelength of the tunable laser in the demonstrated photonic integrated circuit.