Optimal light focusing by a Fresnel mesowavelength phase plate with stepped zone profile
Yu.E. Geints, E.K. Panina
V.E. Zuev Institute of Atmospheric Optics of Siberian Branch of the Russian Academy of Science, Tomsk, Russia
Keywords: near-field light focusing, Fresnel zone plates, mesowavelength scatterer, diffraction limit
Abstract
The results of numerical simulation of the optical radiation focusing by Fresnel zone plates (ZP) with the wavelength-scale (mesowavelength) dimensions and a two-layer profile of phase ridges are presented. We show that the dimensions and intensity of the focusing area are sensitive to the type of ZP design. By changing the phase step shape (height and width of plate faces) it is possible to significantly improve the characteristics of the light field in the focusing region due to smoothing the wave phase profile after passing through individual ZP layers. A comparison is made with the case of a conventional binary ZP.
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