| Whispering gallery mode microcavities with high quality factor Q and small mode volume V have received extensive attention in the field of modern photonics.They have been widely used in the researches of lasers,biosensors and frequency combs.For the whispering gallery mode microcavity can greatly enhance the interaction between light and matter.Recently,the whispering gallery mode microcavity has been widely studied as a platform to enhance the magneto-optical effect.But until now,polarization coupling in magneto-optical microcavities has not been studied,although it plays a very important role in magneto-optical microcavities.In this paper,we theoretically study the mode characteristics in a magneto-optical microcavity,which is only affected by the Faraday effect.We use the finite element method(COMSOL Multiphysics 5.2a)to establish a theoretical model of the Faraday microcavity and calculate its mode characteristics.We find that in the Faraday microcavity,due to the Faraday effect,the polarization state of the intrinsic mode in the microcavity changed from the linear polarization to the regular elliptical polarization.When the coupling conditions are satisfied,the supermodes are generated through the polarization coupling between two intrinsic modes.Due to the polarization coupling,the orientation angle and ellipticity angle of the polarized ellipses of the supermodes change dramatically.The polarization change of the supermode can be explained by the supermode coupling theory.The mode characteristics of the supermode in the weak coupling region and the strong coupling region are different.Finally,we propose a Faraday microcavity-based current sensor.The effects of microcavity characteristics and applied current on polarization coupling are theoretically studied.In the strong coupling region,the orientation angle of the polarization ellipses of the supermode changes approximately linearly with the applied current.Compared with the weak coupling region,the change of polarization orientation angle increases by two orders of magnitude.This finding validates the feasibility of a Faraday microcavity current sensor.In this paper,the mode characteristics in a Faraday microcavity are studied for the first time.Due to the Faraday effect,polarization coupling can be achieved between two inherent elliptical polarization modes in the microcavity.The mode characteristics are important for understanding the Faraday microcavity.Polarization coupling can change the polarization state of the supermode,so it can be used as a method of polarization modulation. |
