Nanophotonics using high-index dielectrics has opened pathways to engineer and control light at the nanoscale with better confinement and practically no absorption loss. However, the absence of a complete library of high-index dielectric materials hinders the understanding of the full potential for dielectric nanophotonics and constrains us to a very limited range of materials. Generally, as the refractive index goes up, materials become lossy, exhibiting a trade-off between the absorption edge and the sub-bandgap refractive index of a semiconductor, popularly known as the Moss rule, which seems to set an upper limit on the refractive index of a dielectric for a given operating wavelength. Here, we develop the recipe to break this index upper bound, looking for super-Mossian materials. We demonstrate super-Mossian nanophotonics for a larger Q-factor and better phase control based on bulk Molybdenum disulfide. We use Rigorous Coupled Wave Analysis (RCWA) to calculate the distribution of different diffraction orders and the results agree well with experiment.

Aligned carbon nanotubes (CNTs) make a promising platform for thermal radiation applications due to their broadband IR hyperbolic dispersion and their ability to withstand high temperatures. However, their temperature-dependent optical properties remain to be explored. Previously, the thermal stability of CNTs has been studied in helium and hydrogen atmospheres and vacuum, yet ambient air is yet to be explored. Here, we study optical properties of aligned CNTs at high temperatures in ambient air. We show that these films improve thermal stability when coated with a thin layer of dielectric and exhibit broadband IR hyperbolic dispersion at elevated temperatures.