Abstract

The use of lithographic and etching techniques to fabricate phase-only diffractive elements was first demonstrated by d’Auria et al¹ and has now become popular following the improvements in the technology driven by the microelectronics industry. In the usual approach, a staircase approximation to the ideal continuous phase profile is implemented in the substrate using a binary mask-and-etch sequence in which the number of phase levels generated is a power of two. Performance is usually discussed in terms of diffraction efficiency and image quality. Dammann² first showed how to calculate diffraction efficiency for the staircase structures using the Fourier theory. Image quality, for those diffractive elements which form images, has been modeled either using raytrace codes with an infinite index approximation or using brute-force integration of the scalar Kirchhoff equation³.

© 1992 Optical Society of America