Shuman Sun
California Institute of Technology
shumans@caltech.edu
Bio
Shuman Sun is a postdoctoral scholar in the Division of Engineering and Applied Science at the California Institute of Technology. She earned her Ph.D. from the Department of Electrical Engineering at the University of Virginia in 2024, following a B.S. in the School of Physics at the University of Science and Technology of China in 2019. Her research focuses on on-chip optical micro-resonators, with applications in optical frequency combs and integrated quantum circuits. Her work has been published in leading journals, including Nature and Nature Photonics. She is the recipient of several honors, including the Louis T. Rader Graduate Research Award from UVAs ECE Department and the Emil Wolf Outstanding Student Paper Prize at the 2024 Optica FiO+LS conference.
Areas of Research
- Photonics and Quantum Technologies
Low-Noise Microwave Generation on Integrated Photonic Chips
Microwave and millimeter waves are extensively used in radar, communications, and radio astronomy. Nowadays, these applications demand higher resolution, faster data transmission, and broader bandwidth, driving microwave technologies to higher carrier frequencies and lower noise. Photonics microwave technologies stand out thanks to their inherent features of low loss at optical frequencies and high fractional frequency stability. Among these photonic micro/mm-wave oscillators, optical frequency division (OFD) technology has set the record for spectral purity. In OFD systems, optical frequencies can be coherently divided down to microwave frequencies, with frequency noise scaling down simultaneously. This frequency down-conversion is linked by optical frequency combs, a series of optical frequencies with uniform comb line spacing at microwave frequencies. Combined with optical references, optical frequency combs can transfer the reference stability to the comb spacing. OFD systems have been developed over many years, but mostly with table-sized bulk devices. Excitingly, recent advances in integrated photonics have initiated a transformation towards miniaturized OFD systems with chip-scale.
My research focuses on integrated OFD systems on CMOS-compatible integrated photonic platforms. Here, a planar-waveguide-based optical reference coil cavity can provide frequency stability due to its low thermal refractive noise. The frequency stability is then transferred to a soliton frequency comb generated on a waveguide-coupled microresonator. As a result, these OFD demonstrations significantly miniaturize the systems and achieve state-of-the-art performance by setting a record for low noise in integrated photonic mmWave oscillators. Moreover, the waveguide-based devices can be heterogeneously integrated in photonic circuits, facilitating large-volume, low-cost manufacturing for mass-market applications.