Frequency references are indispensable to radio, microwave, and time keeping systems, with far reaching applications in navigation, communi- cation, remote sensing, and basic science. Over the past decade there has been an optical revo- lution in time keeping and microwave generation that promises to ultimately impact all of these areas. Indeed, the most precise clocks and lowest noise microwave signals are now based on a laser with short-term stability derived from a reference cavity. In spite of the tremendous progress, these systems remain essentially laboratory devices and there is interest in the prospect of their miniaturization, even towards systems on a chip. Herein, a chip-based optical reference cavity is described that uses spatial averaging of thermorefractive noise to enhance resonator stability. Stabilized fiber lasers exhibit minimum Allan deviation of 75 Hz at 193 THz optical frequency (relative Allan deviation of 3.9 e−13) at 400 μs averaging time by achieving over 26 dB of phase noise re- duction.
Citation: Nature Physics
Pub Type: Journals
frequency stabilization, Laser stabilization, micro-resonator, phase noise