Microcavity-based narrowband parametric amplifier for carrier recovery in optical coherent self-homodyne detection

We demonstrate all-optical carrier recovery exploring optical parametric amplification (OPA) in a monolithic high-finesse silicon nitride microring cavity. Compared to a nonresonant OPA process in nonlinear waveguides, cavity-based OPA allows a much narrower gain bandwidth by manipulating the intracavity light interactions with a controllable parametric gain, thus facilitating high-resolution carrier extraction without needing a large guard band between the carrier tone and data spectrum. Here, we achieve narrowband OPA with a 22.0 dB peak gain and a bandwidth as low as 15.2 MHz in a 100 μm radius microring cavity, which is applied to implement carrier recovery of a 16QAM optical orthogonal-frequency-division-multiplexing data signal. A highly coherent phase is conserved between the recovered carrier tone and the original data, enabling self-homodyne detection with high data quality and minimized electrical compensation. Our study holds potential to constitute energy-friendly coherent receivers.