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Title: Measurement of sub-fm/Hz 1/2 displacement spectral densities in ultrahigh-Q single-crystal microcavities with hertz-level lasers

Tracing a resonance frequency of a high quality factor (Q) optical cavity facilitates subpicometer displacement measurements of the optical cavity via Pound–Drever–Hall (PDH) locking scheme, tightly synchronizing a laser frequency to the optical cavity. Here we present observations of subfemtometer displacements on a ultrahigh-Qsingle-crystalMgF2whispering-gallery-mode microcavity by frequency synchronization between a 1 Hz cavity-stabilized laser and a resonance of theMgF2cavity using PDH laser-cavity locking. We characterize not only the displacement spectral density of the microcavity with a sensitivity of1.5×1016  m/Hz1/2over the Fourier offset frequency ranging from 15 mHz to 100 kHz but also a 1.77 nm displacement fluctuation of the microcavity over 4500 s. Such measurement capability not only supports the analysis of integrated thermodynamical and technical cavity noise but allows for minute displacement measurements using laser-cavity locking for ultraprecise positioning, metrology, and sensing.

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Publication Date:
Journal Name:
Photonics Research
Page Range or eLocation-ID:
Article No. 1202
Optical Society of America
Sponsoring Org:
National Science Foundation
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