ABSTRACT
Here, we theoretically demonstrate a strategy for efficiently turning whispering-gallery-mode (WGM) responses of a subwavelength dielectric disk through their near-field couplings with common low-order electromagnetic resonances of a dielectric block. Both simulations and an analytical coupled oscillator model show that the couplings are Fano interferences between dark high-quality WGMs and bright modes of the block. The responses of a WGM in the coupled system are highly dependent on the strengths and the relative phases of the block modes, the coupling strength, and the decay rate of the WGM. The WGM responses of coupled systems can exceed that of the individual disk. In addition, such a configuration will also facilitate the excitation of WGMs by a normal incident plane wave in experiments. These results could enable new applications for enhancing light-matter interactions.
ABSTRACT
Here we theoretically investigate the coherent interactions between the quantum emitters with magnetic dipole transitions and subwavelength all-dielectric resonators of whispering gallery modes (WGMs). We extend a semi-analytical method which can efficiently calculate the far-field spectrum of a general hybrid system. Then, a subwavelength sphere with refractive index around n = 3.5 is chosen as the dielectric resonator. Due to the high magnetic field enhancements of the WGMs of the sphere, strong couplings between magnetic quantum emitters and subwavelength WGMs can occur, where a clear Rabi splitting appears on the extinction spectrum of the hybrid system. The match between the relaxation times of the WGMs and emitters are important to efficiently achieve a strong enough coupling. The other parameters including the order of a WGM, the radius, the refractive index, the transition dipole moment and excitation intensity are also important factors that can affect the couplings. Our results pave the way for strong interactions between light and magnetic emitters mediated by subwavelength all-dielectric resonators.
