ABERRATED LENSES FOR GENERATING FLATTENED LASER IRRADIANCE

Expressions for describing Gaussian beams focused by a lens with spher ical aberration have been derived. Numerical results show that, when t he coefficient of the spherical aberration is negative, one can obtain flattened laser irradiance at two positions along the focused field. The larger the coefficient of negative spherical aberration, the large r the flatness is. The effect of the Fresnel number of the focusing le ns on the flattened laser irradiance is also investigated. (C) 1998 Op tical Society of America.