Beams Propagation Modelled by Bi-filters

摘要

In acoustic, ultrasonic or electromagnetic propagation, crossed media areoften modelled by linear filters with complex gains in accordance with theBeer-Lambert law. This paper addresses the problem of propagation in mediawhere polarization has to be taken into account. Because waves are nowbi-dimensional, an unique filter is not sufficient to represent the effects ofthe medium. We propose a model which uses four linear invariant filters, whichallows to take into account exchanges between components of the field. We callit bi-filter because it has two inputs and two outputs. Such a circuit can befitted to light devices like polarizers, rotators and compensators and topropagation in free space. We give a generalization of the Beer-Lambert lawwhich can be reduced to the usual one in some cases and which justifies theproposed model for propagation of electromagnic beams in continuous media.