Effect of surface roughness and complex indices of refraction on polarized thermal emission

We present a series of measurements characterizing the dependence of polarized thermal emission on surface roughness. In particular, we measure the spectrally resolved degree of linear polarization (DOLP) for a series of roughened borosilicate (Pyrex) glass substrates as a function of the roughness parameter Ra, the root-mean-square slope distribution, and observation angle theta. Also measured are a series of smooth glass substrates coated with two particular polymers of interest, i.e., a common commercially available Krylon paint and a chemical-agent-resistant coating paint. The DOLP is measured over a 4-13 microm wave band by using a modified Fourier transform IR spectrometer in which a wire-grid polarizer and a quarter-wave Fresnel rhomb are used in conjunction to measure all four Stokes parameters. In addition, we show an enhanced DOLP due to anomalous dispersion exhibited by the surface material.