Refractometry with Ultralow Detection Limit Using Anisotropic Whispering-Gallery-Mode Resonators

W. Weng, James Anstie, Andre Luiten

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    11 Citations (Scopus)


    © 2015 American Physical Society. The intrinsic sensitivity of whispering-gallery-mode resonators aimed at measuring refractive index can be extremely high, although their practical performance is compromised by temperature fluctuations that masquerade as refractive-index changes. We present a triple-mode approach that delivers simultaneous and independent sensing of temperature and refractive-index changes in the same resonator. The frequency difference between two orthogonally polarized modes is used to sense temperature which is then actively stabilized to ∼1 μK over 15 minutes. We then detect a frequency difference between two modes of different wavelengths to obtain a refractive-index measurement that is free of temperature fluctuations. This triple-mode technique delivers a state-of-the-art detection limit of 8×10-9 refractive-index units, despite the resonator size being 100 times larger than that typically used for sensitive refractometric sensing.
    Original languageEnglish
    Article number044015
    JournalPhysical Review Applied
    Issue number4
    Publication statusPublished - 24 Apr 2015


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