Energy pathways in nanoscale thermal radiation

We show in this letter that when nanoscale radiation between two parallel plates is considered, the Poynting vector is decoupled for each parallel wavevector component (beta) due to the nature of thermal emission, as manifested by the fluctuation-dissipation theorem. The streamlines calculated by tracing the Poynting vector vividly demonstrate that the spectral radiative energy travels in infinite directions along curved lines. Depending on the beta value, the energy pathway may exhibit considerable lateral shift. This letter elucidates the fundamental characteristics of nanoscale thermal radiation that is important for applications, such as near-field optical sensors and energy conversion devices. (C) 2007 American Institute of Physics.