Mid-Infrared Sub-Diffraction Optical Resonators in Polar Semiconductors and Hyperbolic Metamaterials

Optical resonator is an essential element in modern optical and optoelectronic devices. The advances in the field of cavity quantum electrodynamics (CQED) requires high quality optical resonators that goes beyond the diffraction limit of light. Consequently, subdiffraction optical resonator has become the foundation for next-generation mid-infrared (MIR) emitters, sensors, etc. In this work, we demonstrate subdiffraction optical resonators based on two material systems: the polar semiconductors and all-semiconductor hyperbolic metamaterials (HMMs).

We first introduce the basic dielectric property of polar semiconductors as well as the concepts of travelling and localized surface phonon polaritons (SPhP). The numerical simulations and experimental results of subwavelength phononic resonators in GaN are presented. In the second part, the theory of HMM and HMM based optical resonators is introduced, followed by the simulation and experimental results on fabricated devices. We thoroughly investigate the mode volume, Q-factors and radiation patterns of the resonators. Furthermore, the HMM resonators’ optical emission property is investigated using the modified long wavelength approximation (MLWA). Specifically, we thoroughly study the impact on Q-factors, radiative and non-radiative decay rates by changing the resonator geometry and material composition.

As for future work, we show two possible directions with preliminary simulation and experimental results. We first propose the quantum well embedded HMM structures for resonant light-mater coupling and CQED applications, followed by the possibility of using GaN and HMMs as high-index dielectric Mie resonators.