Nano Lett. 12, 1475–1481 (2012)

Experimentally investigating the characteristics of thermal electromagnetic radiation in the near-field is challenging because of its short-range evanescent character. Now, Andrew Jones and Markus Raschke from JILA and the University of Colorado Boulder in the USA have demonstrated that this task can be achieved by combining scattering scanning near-field optical microscopy with Fourier-transform spectroscopy. They used a heated atomic force microscope tip as both a local thermal source and a scattering probe, and employed a Michelson-type interferometer to perform spectral analysis in the mid-infrared. They observed an enhanced spectral energy density in the near-field associated with phonon, phonon–polariton and vibrational resonances. The researchers told Nature Photonics that the findings may have wide implications, ranging from chemical vibrational nano-imaging without the need for an external light source, to a better understanding of nanoscale heat transport and the origin of the Casimir force.