Abstract

High numerical aperture (NA) focusing lenses can focus light into small spots, leading to high resolution and concentration of light. In order to evaluate the performance of these lenses, it is necessary to exploit a formulation that takes into account polarization effects and apodization factor. Formulations for dealing with these effects were developed by Debye, and Hopkins, and generalized by Wolf to analyze aplanatic refractive lenses. Here, we treat both theoretically and experimentally diffractive, rather than refractive, lenses with high NA. We adapt Woofs vectorial formulation and apply it to a diffractive lens. We then calculate the intensity distribution at the focal plane as a function of NA, from which we deduce the spot size, in accordance to two criteria. One is based on the width of the central lobe and the other on the encircled 84 percent of the focused energy [1].

© 2000 IEEE