Heat radiation from long cylindrical objects

Abstract

The heat radiated by objects smaller than or comparable in size to the thermal wavelength can be very different from the classical blackbody radiation as described by the Planck and Stefan-Boltzmann laws. We use methods based on scattering of electromagnetic waves to explore the dependence on size, shape, and material properties. In particular, we explore the radiation from a long cylinder at uniform temperature, discussing in detail the degree of polarization of the emitted radiation. If the radius of the cylinder is much smaller than the thermal wavelength, the radiation is polarized parallel to the cylindrical axis and becomes perpendicular when the radius is comparable to the thermal wavelength. For a cylinder of uniaxial material (a simple model for carbon nanontubes), we find that the influence of uniaxiality on the polarization is most pronounced if the radius is larger than a few micrometers, and quite small for the submicrometer sizes typical for nanotubes.

Heat radiation and transfer for point particles in arbitrary geometries

“…(14) is identified with the electric part of the local EM density of states [54,55]. Note that the HR is proportional to the volume of the particle, a feature that is inherent to small objects [13,30]. We also note that the quantity H (1pp) 1pp is non-negative as is the more general expression…”

“…(A6). One typically applies expansion of the free GF in partial waves of an appropriate basis to have the result in terms of the waves and the scattering matrix of an object [13,30,52,64].…”

“…HR of single macroscopic objects like a semi-infinite plate, a sphere, or an infinitely long cylinder was studied in, e.g., Refs. [10][11][12][13]. HT between two plates [14][15][16], two spheres [17], and a sphere and a plate [18][19][20] is particularly interesting due to its dramatic enhancement in the near-field regime.…”

Fluctuating volume-current formulation of electromagnetic fluctuations in inhomogeneous media: Incandescence and luminescence in arbitrary geometries

“…Here, the unknowns are volume currents within objects rather than surface currents as in FSC, and can therefore easily handle more complex structures, including inhomogeneous bodies with temperature gradients or spatially varying permittivities. In contrast to recently developed scattering-matrix methods, [28][29][30][31][32][33][34][35][36][37][38][39][40] the FVC and FSC methods do not require a separate basis of incoming/outgoing wave solutions to be selected (a potentially difficult task in geometries involving interleaved objects or complex structures favoring nonuniform spatial resolution), although VIE can be used to compute the scattering matrix if desired. We show that regardless of which quantity is computed, the final expressions for power and momentum transfer are based on simple trace formulas involving well-studied VIE and current-current correlation matrices that encode the spectral properties of fluctuating sources.…”

“…14,21 These include time-and frequency-domain methods where the power transfer or force on an object is obtained via integrals of the flux or Maxwell stress tensor, or equivalently EM Green's functions, along some arbitrary surface enclosing the body. 36,[73][74][75][76][77][78][79][80] Recent techniques forgo surface integrations altogether in favor of unfamiliar but more efficient expressions involving traces of either scattering 31,33,34,[37][38][39]81,82 or boundary-element 26,27,83 matrices. Regardless of the choice of unknowns, in practical implementations the latter are expanded in terms of either delocalized spectral bases (e.g.…”