Advances in photonic integrated circuit optoelectronic oscillators for next-generation sensing applications

The most recent advancements in photonic integrated circuits (PICs)-based optoelectronic oscillators (OEOs) have made it possible to generate low-phase-noise and frequency-stable microwave signals, which has resulted in the creation of new prospects for high-resolution sensing. This review focuses on the latest developments in monolithic and hybrid photonic integration, which are based on silicon, InP, and SiN. These advancements facilitate the compact implementation of lasers, modulators, detectors, and other OEO components, while simultaneously reducing system footprint and packaging complexity. We present promising emerging architectures based on parity-time symmetry, Fourier-domain mode-locking, and adaptive feedback for the improvement of mode selection, waveform generation, frequency stability, and spectral purity using potential applications in RF/microwave sensing, LiDAR ranging, environmental and biomedical monitoring, and quantum interfaces. Recent breakthroughs in thermal management, phase noise reduction, and wafer-scale integration are highlighted. Future directions will focus on AI-controlled tuning, co-design optimization, and deployable sensor-on-chip solutions for IoT, 5G/6G, and quantum networking.