Microrod Optical Frequency Reference in the Ambient Environment

Optical and microwave reference signals with high phase coherence are needed for precision measurement and advanced technologies, especially as ultrastable signal generators move from the laboratory to the wider world. The authors explore laser-frequency stabilization with respect to a monolithic microresonator, housed without complex ambient-isolation systems. A comprehensive analysis of technical noise shows how to achieve laser coherence that is limited only by ambient thermal noise, and successful generation of a low-noise microwave signal reveals fundamental coherence between the optical and microwave frequency domains.