Controlling thermal radiation by photonic quantum well structure with zero-averaged-refractive-index gap

Abstract

Based on Kirchoff's second law, we investigate the spectral-directional thermal emissivity of a photonic quantum well (PQW) structure with a zero-averaged-refractive-index (zero-n¯) gap coating on an absorbing substrate. It is shown that the thermal emission through tunneling modes having frequencies in the zero-n¯ gap is not only weakly dependent on the emission angle and polarization state but also insensitive to the unit-cell size scaling of the barrier photonic crystal. More importantly, the PQW structure promises the frequency-selective thermal emission for both TE and TM polarization states along a well-defined direction. This may result in designing thermal antennas.