Evanescent fields in physics and their interpretations in terms of flowgraphs.

Evanescent waves and fields play an important role in microwaves, quantum mechanics, optics and elastic waves. Because electromagnetic waves in waveguides have dispersion characteristics similar to those of a unidimensional de Broglie wave, there is a close analogy between quantum mechanical tunneling and the transition through an attenuating sector of a waveguide. Microwave 'evanescent mode' filters, quantummechanical tunneling resonance and optical frustrated total internal reflection filters are compared in light of this analogy. The flowgraph technique and 'unit real' function representation are shown to be effective in discussing the interdependence of incident and reflected waves in various locations in multilayered structures. In electrognetic and elastic waves, the role of evanescent waves is significant in the case of incident beams of limited extent. The role of equivalent circuits of transverse resonance is discussed in the context of oscillatory natural modes determining the character of propagating fields. [ABSTRACT FROM AUTHOR]