title: Thermal infrared near-field spectroscopy.
abstract: Despite the seminal contributions of Kirchhoff and Planck describing far-field thermal emission, fundamentally distinct spectral characteristics of the electromagnetic thermal near-field have been predicted. However, due to their evanescent nature their direct experimental characterization has remained elusive. Combining scattering scanning near-field optical microscopy with Fourier-transform spectroscopy using a heated atomic force microscope tip as both a local thermal source and scattering probe, we spectroscopically characterize the thermal near-field in the mid-infrared. We observe the spectrally distinct and orders of magnitude enhanced resonant spectral near-field energy density associated with vibrational, phonon, and phonon-polariton modes. We describe this behavior and the associated distinct on- and off-resonance nanoscale field localization with model calculations of the near-field electromagnetic local density of states. Our results provide a basis for intrinsic and extrinsic resonant manipulation of optical forces, control of nanoscale radiative heat transfer with optical antennas, and use of this new technique of thermal infrared near-field spectroscopy for broadband chemical nanospectroscopy.
authors.affiliation: Department of Physics, Department of Chemistry, and JILA, University of Colorado, Boulder, Colorado 80309, USA.
authors.forename: Andrew C
authors.initials: AC
authors.lastname: Jones
authors.forename: Markus B
authors.initials: MB
authors.lastname: Raschke
mesh_terms: D004867:Equipment Design; D019544:Equipment Failure Analysis; D018625:Microscopy, Atomic Force / Q000295:instrumentation*; D036103:Nanotechnology / Q000295:instrumentation*; D019265:Spectroscopy, Near-Infrared / Q000295:instrumentation*; D013817:Thermography / Q000295:instrumentation*