Experimental characterizations of micro-array of binary Fresnel lenses fabricated by electron beam lithography

Abstract

In this paper, Micro-scale Fresnel lenses array were fabricated by exposing electron beam on poly (methyl methacrylic) PMMA, photoresist in the region between ?_??−1/3 and ?_?? on ???_? substrate, where ?=?,?,……??. Each unit of these Fresnel lenses has a maximum external diameter of ??.????, a Focal length of ??.????? and the ?-number of ?.??. The total number of rings of this Fresnel lens is ?? and its grating pitch on the periphery is ??? ??. High transmission efficiency of 93.7% was obtained at the wavelength of 650 nm for the thickness of the PMMA, photoresist of 250 nm.