Sub-Hz linewidth integrated photonic microwave generation based on a low-noise hybrid InP/Si <sub>3</sub> N <sub>4</sub> comb laser
Jiachen Li, Liuyan Han, Dong Wang, Minghua Chen, Dechao Zhang, Han Li
Abstract
Low-noise microwave generation is crucial for advanced applications such as 6G millimeter-wave communications, satellite communications, and synthetic aperture radar systems. Traditional microwave sources encounter challenges in meeting stringent performance requirements while maintaining low size, weight, and power consumption (SWaP) at ever-increasing high frequencies. Photonic microwave generation is a promising solution to overcome these limitations, particularly when implemented with chip-scale integration using a simple yet efficient architecture. Here, we propose a chip-scale integrated photonic microwave generator (IPMG) scheme that features a low-noise hybrid InP / Si 3 N 4 comb laser based on the self-injection locking mechanism, in conjunction with the optic-electro-optic feedback to further enhance the RF generation performance. The proof-of-concept IPMG prototype has demonstrated superior performance, highlighting an ultra-narrow RF intrinsic linewidth of 0.8 Hz, low single-sideband phase noises of −92.1 dBc/Hz at 10 kHz offset and −128.3 dBc/Hz at 1 MHz offset, and excellent frequency stability with only 16 kHz fluctuations over 5 min. This work marks a substantial advancement in the development of fully integrated photonic microwave generators by unifying good performance, architectural simplicity, and low SWaP.