The propagation of single-cycle terahertz pulses in random media

Abstract

We describe what are to our knowledge the first measurements of the propagation of coherent, single-cycle pulses of terahertz radiation in a scattering medium. We measure the propagation constants for pulses in a dense collection of spherical scatterers, and compare to the predictions of the quasi-crystalline approximation. Even though the fractional volume in our measurements exceeds the limit of validity of this model, we find that it still predicts certain features of the propagation with reasonable accuracy. By measuring the transmission as a function of the length L of the medium, we extract the scattering mean free path lambdasc (o) over a broad bandwidth. We observe variations in lambda sc ranging over nearly two orders of magnitude, and covering the entire thin sample regime from L/lambda sc << 1 to L/lambdasc ∼10