Optical pulse propagation through a slab of random medium

Abstract

Tractable analytic expressions are developed for the expected broadening that a Gaussian space-time optical pulse experiences as it propagates through a slab of random medium confined to a portion of the propagation path between the input and output planes. The analytic results developed in this paper are based on the modified von Karman spectrum for refractive index fluctuations and the Rytov method which restricts the validity of the results to the weak optical turbulence regime. It is further assumed that the Gaussian beam is collimated and that the Gaussian pulse is narrowband with respect to the carrier frequency which, for optical frequencies, requires pulse widths greater than 20 fs. The results in this paper are given for both near and far fields and it is shown that when the thickness of the slab of random medium is the total propagation distance, the results given in this paper agree with the results for an extended random medium. Examples are given for unmanned air vehicle (UAV) to low Earth orbit (LEO) satellite and LEO-to-LEO crosslinks.