부산대학교 도서관

One intriguing use for a Fresnel zone plate is as a replacement for a hyperbolic lens in a focusing system. Traditionally, zone plates have been used to convert a diverging wave into a plane wave, or vice versa, mimicking the functionality of a plano-convex hyperbolic lens. However, in many focusing systems, both the source and the focal point are located near the focusing element. A zone plate can be designed to replace a doubly-hyperbolic lens in this type of system, reducing the size and weight of the focusing element [1]. The penalties for using the zone plate, however, are a reduction in power delivered to the focal point and a limited operating bandwidth [2]. In this paper, the body-of-revolution finite-difference time-domain (BOR-FDTD) method is used to study the performance of a Fresnel zone plate in a focusing system. Results from a comparison of a zone plate with a doubly-hyperbolic lens will be presented to illustrate the benefits and limitations of the zone plate.