Wave-optical structure design with the local plane-interface approximation

The design of an optical element profile with specified transmission functi on for a given incident wave is of fundamental concern in optical design. A well-known example is the design of an aspherical surface in order to real ize a spherical phase-only transmission. Various wave-optical system design methods lead to transmission functions as a first step. Then, often the th in-element approximation is applied in a second step to obtain an element s tructure with the desired transmission. However, if the refraction at the o ptical interface cannot be neglected, the thin-element approximation is not valid. In this case, a higher version of the local plane-interface approxi mation can be used for the element structure design. An algorithm for this model is introduced and its characteristics are discussed for the example o f a non-paraxial Gaussian-to-tophat beam shaping element.