EVANESCENT FIELD

In a waveguide , a time -varying field having an amplitude that decreases monotonically as a function of transverse radial distance from the waveguide, but without an accompanying phase shift . ( 188 ) Note 1: The evanescent field is coupled, i.e., bound, to an electromagnetic wave or mode propagating inside the waveguide. Note 2: The evanescent field is a surface wave . Note 3: In fiber optics , the evanescent field may be used to provide coupling to another fiber. [After 2196 ]