Uniform asymptotic approximation of the evanescent part of the Green's tensor

The evanescent part of optical radiation from a localized source decays rapidly with distance. We have studied the asymptotic behavior of this radiation by means of the Green's tensor. This tensor can be expressed in terms of four auxiliary functions M-i(q, 0), with q the (dimensionless) distance to the source and 0 the polar angle. We have derived asymptotic approximations for these functions, with Bleistein's method, which hold uniformly for all angles 0. Our result generalizes the result of Berry for the evanescent part of the free space scalar Green's function. We have illustrated graphically the accuracy of our approximation. (C) 2002 Elsevier Science B.V. All rights reserved.