Finite-substrate-thickness cylindrical diffractive lenses: exact and approximate boundary-element methods

A novel approach based on the boundary-element method (BEM) with exact and approximate Green's functions is presented for the analysis of the performa nce of finite-substrate-thickness cylindrical diffractive lenses. This appr oach can be applied to the analysis of lenses with thicknesses of thousands of wavelengths for both TE and TM polarization. Multiple interference reso nance effects between the upper and the lower boundaries of the lens are in cluded. Also, for the cases when multiple interference resonance effects ca n be neglected, another approach based on the BEM with a modified approxima te Green's function is developed. It is shown that the latter approach corr esponds to the cascaded application of the BEM as previously published [App l. Opt. 37, 34, 6591 (1998)]. To illustrate the advantages of the approache s presented, a cylindrical diffractive lens with a substrate thickness of 2 mm is analyzed. It is not possible to analyze this large-substrate-thickne ss lens with the previously published cascaded application of the BEM. (C) 1999 Optical Society of America [S0740-3232(99)00906-0].