Ultrastable vacuum-gap Fabry–Perot cavities operated in air
Yifan Liu, Naijun Jin, Dahyeon Lee, Charles A. McLemore, Takuma Nakamura, Megan Kelleher, Haotian Cheng, Susan Schima, Nazanin Hoghooghi, Scott A. Diddams, Peter T. Rakich, Franklyn Quinlan
Abstract
We demonstrate a vacuum-gap ultrastable optical reference cavity that does not require a vacuum enclosure. Our simple method of optical contact bonding in a vacuum environment allows for cavity operation in air while maintaining vacuum between the cavity mirrors. Vacuum is maintained long term, with no observed degradation in cavity stability for over 1 year after bonding. For a 1550 nm laser stabilized to a 9.7 mL in-vacuum bonded cavity, the measured Allan deviation is 2.4×10 −14 at 1 s, and its phase noise is thermal-noise-limited from 0.1 Hz to 10 kHz, reaching about −105dBc/Hz at 10 kHz offset frequency. This represents the highest stability of any oscillator operated without a vacuum enclosure, to our knowledge. Furthermore, we demonstrate a 0.5 mL in-vacuum bonded cavity created using microfabricated mirrors and cavity dicing, with phase noise reaching −95 dBc/Hz at 10 kHz offset frequency. By relieving the need for high-vacuum enclosures, we greatly enhance the portability and utility of low-noise, compact, cavity-stabilized lasers, with applications ranging from environmental sensing to mobile optical clocks to ultralow-noise microwave generation.