INTENSITY DISTRIBUTION OF GAUSSIAN BEAMS FOCUSED BY A LENS WITH SPHERICAL-ABERRATION

Spherical aberration (SA) is considered in a focusing Gaussian beam sy stem. Numerical calculation results are given, in which the axial and transverse light intensity distributions along the focused field are g iven. It is shown that a lens with negative SA can achieve a smaller f ocused beam radius and larger maximum axial focused light intensity th an for the no-SA case; and at the some positions, we can obtain a flat tened Gaussian beam distribution. For a lens with positive SA, the max imum axial focused intensity is smaller and the focused beam radius is larger than for the no-SA case. The effects of the Fresnel number of the lens on the focused light intensity distribution are also discusse d. It is noted that the smaller the Fresnel number of the lens, the le ss the influence of the SA coefficients on the focused light intensity distribution. (C) 1998 Elsevier Science B.V. All rights reserved.