Low-Noise Microwave Generation With Optical Microresonators

Optical frequency combs provide an equidistant grid of optical frequency components, enabling a wide array of diverse and new technologies [1]. One such application is photonic microwave generation where optical frequency combs provide unprecedented low-noise performance via optical frequency division [2]. Although providing excellent performance, it comes at the expense of size and complexity. In this work, we pursue a different route to provide both a compact and low-noise microwave source by direct microwave generation with microresonator based optical Kerr frequency combs (KFC) [3] that are formed via dissipative Kerr temporal solitons (DKS) in the microresonators [4]. A unique aspect of KFCs is their wide comb spacing (10 GHz-1THz) due to the small dimensions of the resonator. This enables a wide range of applications including optical communications, spectroscopy and direct generation of microwave signals. For this latter application, crystalline resonators are appealing over other microresonator platforms, as their low thermorefractive coefficient imply that the noise introduced by the resonator will be very low.