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arXiv · 2012.12446

Dielectric perturbations: anomalous resonance frequency shifts in optical resonators

Farhan Azeem·Luke S. Trainor·Patrick A. Devane·Daniel S. Norman·Alfredo Rueda·Nicholas J. Lambert·Madhuri Kumari·Matthew R. Foreman·Harald G. L. Schwefel
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Abstract

Small perturbations in the dielectric environment around a high quality whispering gallery mode resonator usually lead to a frequency shift of the resonator modes directly proportional to the polarizability of the perturbation. Here, we report experimental observations of strong frequency shifts that can be opposite and even exceed the contribution of the perturbations' polarizability. The mode frequencies of a lithium niobate whispering gallery mode resonator are shifted using substrates of refractive indices ranging from 1.50 to 4.22. Both blue- and red-shifts are observed, as well as an increase in mode linewidth, when substrates are moved into the evanescent field of the whispering gallery mode. We compare the experimental results to a theoretical model by Foreman et al. and provide an additional intuitive explanation based on the Goos-Hänchen shift for the optical domain.

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Farhan Azeem, Luke S. Trainor, Patrick A. Devane, Daniel S. Norman, Alfredo Rueda, Nicholas J. Lambert, Madhuri Kumari, Matthew R. Foreman, Harald G. L. Schwefel. 2020-12-23. Dielectric perturbations: anomalous resonance frequency shifts in optical resonators. https://doi.org/10.1364/ol.420791

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