Refractory nanophotonics, or nanophotonics at high temperatures, can revolutionize many applications, including novel infrared sources, ultrahigh density data storage, innovative chemical sensing techniques, and waste heat recovery. In particular, extremely anisotropic optical materials stable at high temperatures are very interesting and promising for revolutionary applications. However, the lack of such materials limits the scope of nanophotonics and its application at high temperatures. Here, we demonstrated that macroscopically aligned carbon nanotubes make an excellent refractory material platform for nanophotonic devices. Aligned carbon nanotubes are thermally stable up to 1600 °C and exhibit extreme anisotropy: metallic in one direction and insulating in the other two directions. Such extreme anisotropy results in an exceptionally large photonic density-of-states (PDOS) over a broadband spectrum range (longer than 4.3 μm) in the mid-infrared, manifesting as strong resonances in deeply subwavelength-sized cavities. We demonstrate polarized, spectrally selective, thermal emission from aligned carbon nanotube films and indefinite cavities of volume as small as ∼λ³/700 operating at 700 °C. These experiments suggest that aligned carbon nanotubes enhance PDOS and hence also thermal photon density by over 2 orders of magnitude, making them a promising refractory nanophotonics platform.

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