Evanescent and propagating fields of a strongly focused beam.

Evanescent- and propagating-field distributions from a strongly-focused-wave beam with subwavelength waist w(a) << lambda as a function of polar angle and distance are investigated. Exact amplitudes and intensities of evanescent E(ev) and propagating E(p) fields, including interference terms, are presented both in near- and far-field regions. It is shown that the amplitude of E(ev) decays as exp(-r/w(a)) in the near-field region and that evanescent waves do not contribute to the far field in the forward direction as they do in the transverse directions theta = pi/2, even though the oscillating evanescent field of the same strength but opposite in sign to the propagating field exists in the transverse plane.