title: Chasing the thermodynamical noise limit in whispering-gallery-mode resonators for ultrastable laser frequency stabilization.
abstract: Ultrastable high-spectral-purity lasers have served as the cornerstone behind optical atomic clocks, quantum measurements, precision optical microwave generation, high-resolution optical spectroscopy, and sensing. Hertz-level lasers stabilized to high-finesse Fabry-Pérot cavities are typically used for these studies, which are large and fragile and remain laboratory instruments. There is a clear demand for rugged miniaturized lasers with stabilities comparable to those of bulk lasers. Over the past decade, ultrahigh-Q optical whispering-gallery-mode resonators have served as a platform for low-noise microlasers but have not yet reached the stabilities defined by their fundamental noise. Here, we show the noise characteristics of whispering-gallery-mode resonators and demonstrate a resonator-stabilized laser at this limit by compensating the intrinsic thermal expansion, allowing a sub-25 Hz linewidth and a 32 Hz Allan deviation. We also reveal the environmental sensitivities of the resonator at the thermodynamical noise limit and long-term frequency drifts governed by random-walk-noise statistics.High-quality optical resonators have the potential to provide a miniaturized frequency reference for metrology and sensing but they often lack stability. Here, Lim et al. experimentally characterize the stability of whispering-gallery resonators at their fundamental noise limits.
authors.affiliation: Mesoscopic Optics and Quantum Electronics Laboratory, University of California, Los Angeles, CA, 90095, USA. jklim001@ucla.edu.
authors.forename: Jinkang
authors.initials: J
authors.lastname: Lim
authors.affiliation: OEwaves Inc., 465 North Halstead Street, Suite 140, Pasadena, CA, 91107, USA.
authors.forename: Anatoliy A
authors.initials: AA
authors.lastname: Savchenkov
authors.affiliation: OEwaves Inc., 465 North Halstead Street, Suite 140, Pasadena, CA, 91107, USA.
authors.forename: Elijah
authors.initials: E
authors.lastname: Dale
authors.affiliation: OEwaves Inc., 465 North Halstead Street, Suite 140, Pasadena, CA, 91107, USA.
authors.forename: Wei
authors.initials: W
authors.lastname: Liang
authors.affiliation: OEwaves Inc., 465 North Halstead Street, Suite 140, Pasadena, CA, 91107, USA.
authors.forename: Danny
authors.initials: D
authors.lastname: Eliyahu
authors.affiliation: OEwaves Inc., 465 North Halstead Street, Suite 140, Pasadena, CA, 91107, USA.
authors.forename: Vladimir
authors.initials: V
authors.lastname: Ilchenko
authors.affiliation: OEwaves Inc., 465 North Halstead Street, Suite 140, Pasadena, CA, 91107, USA.
authors.forename: Andrey B
authors.initials: AB
authors.lastname: Matsko
authors.affiliation: OEwaves Inc., 465 North Halstead Street, Suite 140, Pasadena, CA, 91107, USA.
authors.forename: Lute
authors.initials: L
authors.lastname: Maleki
authors.affiliation: Mesoscopic Optics and Quantum Electronics Laboratory, University of California, Los Angeles, CA, 90095, USA. cheewei.wong@ucla.edu.
authors.forename: Chee Wei
authors.initials: CW
authors.lastname: Wong