Probing Planck's law with incandescent light emission from a single carbon nanotube

We present thermal and electron micrographs of an incandescent lamp constructed from a multiwalled carbon nanotube, and correlate the subwavelength optical information with the underlying nanoscopic structure. Remarkably, the heat equation and Planck's law together give a precise, quantitative description of the light intensity as a function of input power, even though the nanotube's small size places it outside the thermodynamic limit.