Hartmann wavefront sensor based on multielement amplitude masks with apodized apertures

Abstract

A theoretical and experimental study of a Hartmann sensor intended for measurements of light beam wavefronts and implemented on the basis of multielement amplitude masks with apodized apertures is presented. We perform a comparative analysis of the optical performance of the amplitude masks with hard-edge circular apertures and half-tone masks (HTMs) with apodized apertures forming smooth fast decaying optical responses on a photosensor. A technique for fabricating chromium HTMs is developed, which is based on laser thermochemical method of recording. This technique includes two main stages: first – the exposure of a chromium film by a focused laser beam, whose power is varied in a smooth and nonlinear manner versus the required density of HTM’s structure, and second – the developing of the film in a selective etcher. Specimens of HTMs consisting of 64×64 Gaussian apertures were fabricated and applied in a modified Hartmann sensor to measure the wavefront of powerful laser systems.