Monolithic all-optical phase regenerator via parity-time symmetry

Abstract Optical phase represents a fundamental dimension of electromagnetic waves, where the elimination of phase noise is crucial in various applications. Kerr-mediated all-optical phase regeneration can mitigate noise on-the-fly but requires complicated and bulky phase-locking circuits to yield high-fidelity optical phase coherence. Extending this approach to practical applications, the challenges are to develop miniaturized regenerators without trading off performance, a critical barrier rooted in the fundamental conflict between the high-Q environment required for phase locking and the low-Q environment needed for high processing speed. Here we demonstrate a monolithic all-optical phase regenerator within an integrated coupled resonator, with processing rate exceeding the high-Q cavity linewidth by a factor of over 30. The key is exploiting Kerr-induced synchronization (KIS) as a passive, electronics-free phase-locking mechanism within a parity-time (PT) symmetric design, which simultaneously supports high-Q mode for KIS and low-Q mode for high-speed signal processing. Experimentally, phase regeneration at Gigabits per second rates is achieved using MHz-linewidth cavity, with phase distortion up to ± 45° fully regenerated to the back-to-back level. This work demonstrates a paradigm shift in optical phase regeneration from benchtop assemblies to a monolithic chip via non-Hermitian optics, opening new avenues for next-generation, densely integrated chip-scale photonic processors across communications, quantum technologies, sensing, and metrology.