A High Stability, Monolithic, Spiral Reference Cavity&Integrated Source for Application to Ultra-stable Microwave Generation

Frequency division of a stable optical reference using frequency combs is a proven technique to create the highest stability microwave signals, especially for close-to-carrier offset frequencies. The prospects for miniaturization of these systems are good based on recent progress in microcombs, high-Q microresonators, and coherent sources. However, there remain technical issues that must be solved. In this effort we attack the problem of miniaturization of the stable optical source. This source sets overall stability of the microwave oscillator upon frequency division and relies upon a special reference cavity with very low thermal-induced frequency fluctuations. In Phase I, a new approach will be used to create integrated reference cavities that are both high Q and that feature very low thermo-refractive noise. In addition to being inherently robust with respect to shock and vibration this reference cavity will also utilize semiconductor process techniques that the principal investigator and coworkers have previously used to create high-efficiency microwave repetition rate microcombs on a chip. If Phase I is successful, the reference cavity will be combined with a high coherence laser in Phase II to create a high-stability optical reference. This optical reference will then be tested at NIST in a 10 GHz oscillator system.