Efficiency analysis of diffractive lenses

Multilevel diffractive optical elements are necessary for achieving high-ef ficiency performance. Here the diffraction efficiency of a multilevel phase -only diffractive lens is analyzed. Approximate, as well as more accurate, approaches are presented. Both plane-wave and Gaussian illumination are dis cussed. It is shown that for many practical cases the diffraction efficienc y can be determined by only a single parameter that takes into account the spatial bandwidth product as well as the focal length of the lens and the i llumination wavelength. The analysis is based on the scalar theory and the thin-element approximation. Justification for doing this is presented. The results are valid for lenses with at least F/5. (C) 2001 Optical Society of America.