Since their invention over two decades ago, optical frequency combs (OFCs) have enabled dramatic advances in the way we measure light and time. The utility of these devices follows from their characteristic output of broadband optical frequencies along with their well-timed pulsed output. Optical frequency combs are now used in a multitude of applications including microwave and optical frequency synthesis, synchronization between state-of-the-art atom-based clocks, as well as atomic and molecular spectroscopy. However, the complexity and scale of OFCs generally limits them to specialized optics laboratories. In response, there has been a significant effort to leverage advances in nano- and micro-fabrication to produce compact chip-based optical frequency comb devices on the microscale. These photonic “microcombs” utilize their small size, material optical nonlinearity, and strong optical confinement to produce high quality frequency combs with distinct advantages in efficiency, scalability and compatibility with full photonic integration.

However, along with challenges in fabrication, such small devices are especially susceptible to sources of thermal noise which couple to the phase stability of the optical frequency comb and ultimately limit their performance for precision applications. This talk will outline our current efforts in investigating and mitigating the sources of phase noise in photonic OFC devices. Our work focuses on the silicon nitride (SiN) microring resonator platform where we have developed our capabilities in design and fabrication, including the novel application of metal liftoff for producing thick nitride, high quality factor (Q factor) ring resonators. With these capabilities and techniques for mitigating phase noise, we aim to produce high Q photonic OFCs with state of the art phase noise performance.