(a) Schematic of a PC sample, mounted on a thermal heater. When it is heated to an elevated temperature, it emits radiation through the DBR top surface into the free space (red arrows). (b) Schematic of the same PC sample, but its entire DBR top surface is coated with a layer of black-CNT (A = 99.9%). (c) Schematic of a PC sample, having a small fraction (~30%) of its top surface covered with black-CNT. (d) A top view of the partially coated sample. The red circles indicate the placement of an optical aperture, to be scanned step-by-step across the sample. (e) A cross section SEM image of our resonant cavity tungsten-photonic crystal (W-PC).