Heat radiation from long cylindrical objects

TL;DR

This paper investigates how the heat radiation from long cylindrical objects varies with size, shape, and material properties, especially focusing on polarization effects for different radii relative to the thermal wavelength.

Contribution

It provides a detailed analysis of electromagnetic scattering to understand radiation and polarization from cylinders, including uniaxial materials like carbon nanotubes.

Findings

Radiation is polarized parallel to the axis when radius is much smaller than thermal wavelength.

Polarization becomes perpendicular as radius approaches the thermal wavelength.

Uniaxiality significantly affects polarization for larger cylinders, but not for nanotube-sized objects.

Abstract

The heat radiated by objects small or comparable to the thermal wavelength can be very different from the classical blackbody radiation as described by the laws of Planck and Stefan-Boltzmann. We use methods based on scattering of electromagnetic waves to explore the dependence on size, shape, as well as 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 microns, and quite small for submicron sizes typical for nanotubes.