Optical Frequency Division Using High-Q Integrated Photonics

Citation

Ji, Qingxin (2025) Optical Frequency Division Using High-Q Integrated Photonics. Dissertation (Ph.D.), California Institute of Technology. doi:10.7907/wjew-9m88. https://resolver.caltech.edu/CaltechTHESIS:05312025-234853354

Abstract

Optical frequency division (OFD) coherently transfers the high spectral purity of optical transitions down to a microwave tone. This coherence transfer makes possible numerous modern technologies, including microwave synthesizing, optical atomic clocks, time and frequency transfer, optical frequency synthesizing, etc. In this thesis, I present advancements in using photonic-chip-based components to perform the OFD with high-performance. Along this pathway, chip-integrated, low-SWaP optical frequency combs are developed using coupled ring resonators. The key features include efficient dispersion tuning using the Moire speedup effect and ultra-high Q factor up to 100 million for an energy-efficient microcomb operation. To illustrate, recording low-noise microwave among those using integrated photonics are demonstrated. In moving towards a deliverable assembly, hybrid system packaging is demonstrated with characterized long-term stability. Ultrafast tuning control using integrated piezoelectric actuation simplifies the system architecture. In particular, an integrated, low-noise PDH locking system, and a full frequency-stabilized microcomb are demonstrated.

Thesis Files