Particle-size effects on the terahertz transmittance of metallic particle ensembles: Comparison with effective medium theory

We investigate the transmittance of fixed-length ensembles of spherical particles having average radii ranging over two orders of magnitude. The transmittance is interrogated at discrete frequencies in the terahertz regime where the particle radius is subwavelength by at least an order of magnitude. A nonmonotonic dependence of the transmittance on particle radius is observed. As a function of increasing particle size, the transmittance increases to a peak value and then decreases toward zero. Calculations of the complex effective permittivity of the ensemble yield predicted transmittance curves that accurately describe the transmittance decrease as a function of increasing particle size. (C) 2010 American Institute of Physics. [doi:10.1063/1.3430547]