  We introduce and experimentally demonstrate a new class of electrically
driven thermal emitter based on globally aligned carbon nanotube metamaterials
patterned as nanoscale ribbons. The metamaterial ribbons exhibit electronic and
photonic properties with extreme anisotropy, which enable low loss,
wavelength-compressed hyperbolic photonic modes along one axis and high
electrical resistivity and efficient Joule heating along the other axis.
Devices batch-fabricated on a single chip emit linearly polarized thermal
radiation with peak wavelengths dictated by their hyperbolic resonances, and
their low thermal mass yields infrared radiation modulation rates as high as
one megahertz. As a proof-of-concept demonstration, we show that two sets of
thermal emitters on a single chip, each operating with different spectral peak
positions and modulation rates, can be used to sense carbon dioxide with a
single detector. We anticipate that the combination of batch fabrication, wide
modulation bandwidth, and customized spectral tuning with hyperbolic chip-based
thermal emitters will enable new modalities in multiplexed infrared sources for
sensing, imaging, and metrology applications.
