CAREER: Ultralow phase noise signal generation using Kerr-microresonator optical frequency combs

Since their invention two decades ago, optical frequency combs have become one of the most important tools in precision measurement. They are used in trace gas spectroscopy for the detection of chemical hazards and disease-correlated biomarkers, in stellar spectroscopy in the search for Earth-like exoplanets, and as critical components of optical atomic clocks. Although their use is now ubiquitous, optical frequency combs are largely confined to specialized optics laboratories. However, this is changing. Recently, optical frequency combs have been realized using chip-scale microring cavities and the nonlinear Kerr effect. The promise of these “microcombs” lies in the possibility of replacing a research laboratory dedicated to precision measurement with a comb-on-a-chip platform that can perform precision measurements far from the optics lab. As with many precision measurement instruments, microcomb precision is limited by material thermal noise, a limitation which is worsened by the small volume of the microring. Building on recent work investigating how material noise affects comb precision, Drake and her team will develop a technique for microcomb noise reduction based on novel cavity geometries and comb operation. Decoupling material thermodynamics from the properties of the comb light represents an important and necessary milestone for the use of microcombs as state-of-the-art precision measurement instruments. The PI proposes an in-depth investigation of the coupling of material thermal noise to the properties of microresonator optical frequency combs with the dual goals of better understanding and predicting the fundamental noise processes in microresonator optical frequency combs and creating microcomb systems with reduced thermal phase noise in both their microwave and optical frequencies. While the thermodynamics of matter are generally well understood, the intersection of thermal noise and nonlinear optics remains largely unexplored. In microcombs, the transduction of thermal fluctuations in the resonator material properties to noise on properties of the comb light (the microwave repetition rate or the optical comb modes) is highly dependent on the details of the comb state, include the Raman self-frequency shift and the presence of dispersive waves. This project encompasses a theoretical and experimental study of the connection between thermal and frequency/phase noise in microresonator frequency combs by introducing geometries and techniques that alter this relationship and that can be utilized to produce ultra-low phase noise signals. The overall goal of the research is the generation of low phase noise signals (primarily microwave and potentially optical as well) in low-cost, room temperature systems with the potential for future photonic integration. The PI will also develop a summer academy for area STEM educators focused on design and construction of optics-based projects (Optical Technology Inventors and Makers Academy, OPTIMA). Attendees will learn the principles of optics and optical design and will be encouraged to create optics projects that can be used as teaching material in their classes. In the long term, the PI plans to expand this program to the wider Albuquerque community by partnering with organizations such as local area makerspaces and the Albuquerque Astronomical Society. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria. NSF Award ID: 2340973 | Program: 01002526DB NSF RESEARCH & RELATED ACTIVIT,01002425DB NSF RESEARCH & RELATED ACTIVIT | Principal Investigator: Tara Drake | Institution: University of New Mexico, ALBUQUERQUE, NM | Award Amount: $558,000 View on NSF Award Search: https://www.nsf.gov/awardsearch/showAward?AWD_ID=2340973 View on Research.gov: https://www.research.gov/awardapi-service/v1/awards/2340973.html