Abstract
We propose a scheme for deriving a high-resolution zone plate from a coarser one by interfering the light from two positive-order foci. We give a theorteical analysis of the process, which we call spatial-frequency multiplication. The analysis requires calculation of diffracted intensities far off axis, and we derive validity conditions for the application of approximate methods to this calculation. Specifically, we show that the Fresnel approximation is useful in many cases, whereas the method of stationary phase is valid for all cases of technological interest. Some practically useful parameter choices are considered for implementation of the zone-plate fabrication method. An example calculation suggests that a zone plate with smallest zone spacing of 13.8 nm may be possible.

This publication has 7 references indexed in Scilit: