Far-field thermal radiation at the optical topological transition*

We develop theoretical description of far-field thermal emission near optical topological transitions (OTTs). OTTs originate from a transformation in the topology of the phase space in the medium which results drastic changes in the photonic density of states. In this work, we show that the unique evolution of this transition leads to a characteristic signature in the far-zone thermal emission. In particular, we find (APL 115, 151906 (2019)) a strong asymmetric pattern of reduced emission near the transition from type-I hyperbolic to dielectric responses present in both naturally available and composite media. The existence of the asymmetric feature should be experimentally observable and can be used as a tool to detect the OTT between type-I hyperbolic and dielectric electromagnetic responses.