Fresnel Zone Plate in Thin Aluminum Film

In this paper, an aluminium Fresnel zone plates is investigated by using frequency dependent finite difference time domain method. Study of the focal spot characteristics versus the relief height of zone plate shows that the height of 50 nm allows to achieve an optimal ratio between width and intensity of the focal spot for both linearly and circularly polarized Gaussian beams at wavelength of 532 nm. The proposed zone plate was fabricated by using technology of electron beam lithography, chemical etching and lift-off process-.