The invention includes a master lens, which initially focuses a laser pulse, and then the pulse passes through a zonal lenslet array, which uses different lenslet elements that provide for predetermined focal lengths so as to establish a three or two dimensional, predetermined dispersion of foci of the laser pulse. The zonal lenslet array of the present invention may be thought of as a variant of a Shack-Hartman wave front sensor, but used for an entirely different application.