Metallic surface-relief on-axis and off-axis focusing diffractive cylindrical mirrors

Metallic surface-relief diffractive cylindrical mirrors are designed for on -axis and off-axis focusing and incidence configurations. These diffractive structures are analyzed by both rigorous and scalar integral methods. Two design methods, based on initial assumptions of zero-thickness and finite-t hickness structures, are presented for determining the zone-boundary locati ons and the surface-relief mirror profiles for the general case of an off-a xis incident plane wave and off-axis focusing. With the use of these method s, continuous diffractive, multilevel diffractive, and continuous nondiffra ctive mirrors were designed. Rigorous analysis is performed for both TE and TM polarizations by using an open-region formulation of the boundary eleme nt method (BEM) suitable for regions of complex refractive index such as fi nite-conductivity metals. Three scalar integral methods corresponding to Di richlet, Neumann, and Kirchhoff boundary conditions are also used to analyz e the diffractive mirrors. The diffracted fields from both the rigorous BEM and the scalar methods of analysis are used to calculate a number of perfo rmance metrics including diffraction efficiency, sidelobe power, total refl ected power, and focal spot size. The performance of the mirrors is evaluat ed, and the accuracy of the various scalar methods is determined. (C) 1999 Optical Society of America [S0740-3232(99)00601-8].