Whispering-gallery-mode resonators: from a novel sensing mechanism to a wireless sensing system (Conference Presentation)

Abstract

Whispering-gallery-mode optical resonators have shown their potentials for sensing applications in recent years owing to significantly enhanced light-matter interactions in a strongly confined volume. Boosting the sensitivity of the sensor and miniaturing the sensing system are two of the most important directions of whispering-galley-mode sensors. In this talk, I will present our recent work on novel sensing mechanism to enhance the sensitivity of a whispering-gallery-mode sensor, and a portable, wireless sensing system which can be fully controlled by smart devices. By tuning two nanoscale scatterers within the mode volume, a whispering-gallery-mode resonator can be steered to non-Hermitian degeneracies, also known as exceptional points. Due to the complex-square-root topology at the vicinity of exceptional points, the frequency splitting induced by a target object (with sufficiently small perturbation) is proportional to the square-root of its perturbation strength, and is thus larger than the frequency splitting obtained in conventional sensing schemes which is proportional to the perturbation strength of the target object. We also demonstrated that, by integrating a packaged sensor, a microcontroller, a wireless transceiver and power supply, we could build a miniature whispering-gallery-mode sensing system with a wireless interface. A customized iOS app has been developed to monitor and adjust the system parameters, and collect and analyze the sensing signals. This wireless sensing system could be employed to measure temperature distribution in a selected area. Our studies help broaden the applications of the whispering-gallery-mode resonators as an innovative sensor platform.