Polarized Light Emission from a Single Hot Carbon Nanotube*

We fabricate nanoscale lamps, incandescent in the visible, which have a filament consisting of a single multiwall carbon nanotube. The radius $r$ of the nanotube is much smaller than the wavelength $\lambda$ of the emitted light, making it a very unusual thermal emitter. Transmission electron microscopy is used to determine the nanotube's axis as well as the parameters of the tube's geometry. We image both light polarizations on a CCD camera simultaneously and observe a degree of polarization between 70\% and 85\% along the tube's axis at visible wavelengths--highly polarized, yet less so than is expected for a conducting antenna. Furthermore, the polarization's variation with wavelength trends opposite to that predicted by classical models and analogy with graphene.