Kerr-microresonator optical frequency combs

Optical frequency combs are specialized lasers that enable extremely precise measurement of frequency and time. In the time domain, combs are a series of pulses that arrive at exact and repeated intervals (like ticks of a clock), and in the frequency domain, they consist of many, evenly spaced optical frequencies (the “teeth” of the frequency comb). Since its inception two decades ago, the optical frequency comb has revolutionized multiple applications in precision science, from optical clock readout to frequency synthesis across the optical and microwave regimes to precision spectroscopy used in the search for exoplanets. Recently, a new optical frequency comb platform based on chip-integrated waveguide microresonators has opened the possibility of comb-enabled science to researchers without access to a specialized optics lab. In this talk, I will give an overview of optical frequency combs and their parallel development with improvements in timekeeping. I will present the physics of comb generation in waveguide microresonators, along with resonator fabrication and a few recent “microcomb” applications. Finally, I will discuss the challenge of thermal noise in microresonators and how one might remove this noise from the comb light to increase precision in frequency synthesis and measurement.