MODAL APPROXIMATION FOR THE ELECTROMAGNETIC-FIELD OF A NEAR-FIELD OPTICAL PROBE

A formalism is given in which the optical field generated by a near-fi eld optical aperture is described as an analytic expansion over a comp lete set of optical modes. This vectoral solution preserves the diverg ent behavior of the near field and the dipolar nature of the far field . Numerical calculation of the fields requires only evaluation of a we ll behaved, one-dimensional integral. The formalism is directly applic able to experiments in near-field scanning optical microscopy when rel atively flat samples are evaluated. (C) 1996 Optical Society of Americ a