Abstract
Cross-polarization coupling (CPC) between coresonant orthogonally polarized modes in a single whispering-gallery microresonator can lead to induced transparency effects. Depending on the CPC strength, coupled-mode-induced transparency (CMIT) or Autler-Townes splitting (ATS) can be observed. Determining the CPC strength is crucial in locating the exceptional point, where CMIT evolves into ATS and an enhancement in sensitivity to perturbations is expected. The CPC strength can be calculated theoretically based on the transverse structure of whispering-gallery modes. Experimentally, however, CPC strength has been inferred only indirectly by fitting the experimental throughput spectrum to a steady-state model. In this work, we propose and demonstrate a direct determination of the CPC strength based on the response of the throughput to a sinusoidal amplitude modulation of the input light. Our experimental results agree with numerical fitting values and are in the same range as predicted by theoretical calculations.
- Received 24 August 2021
- Revised 27 September 2021
- Accepted 15 November 2021
DOI:https://doi.org/10.1103/PhysRevA.104.053534
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