DIRECTIONAL AND ASYMMETRIC MANIPULATION OF ELECTROMAGNETIC THERMAL RADIATION USING SUB-WAVELENGTH NANOSTRUCTURES

Abstract

In this thesis, we employ low-loss dielectric nanostructures combined with anisotropic magneto-optical (MO) materials, to build systematic tuning methods for shaping directional radiation. By deeply revealing the synthesizing mechanisms of MO effects and multipolar resonances, we have proposed a generalized principle to realize asymmetric radiation at an arbitrary direction. Furthermore, we have systematically unveiled the topological nature of perfect absorption associated with spectral phase singularity, further extended such findings to break Kirchhoff's law of thermal radiation in MO-dielectric systems. Based on the revealed mechanisms and proposed strategies, we have provided experimental evidence that a large violation of Kirchhoff’s law can be realized under a moderate magnetic field using ultrathin epsilon-near-zero InAs films. We believe that the revealed mechanisms associated topological nature and MO effects in shaping asymmetric radiation spectra will stimulate more comprehensive studies in nonreciprocal radiation, which will renovate the development of next-generation energy devices with enhanced efficiency.