Synthesis of Nano-Optical Elements for Forming 3D Images at Zero Diffraction Order

Abstract

A method is proposed to compute and synthesize a nano-optical element to produce a new visual effect: a 3D image formed in the vicinity of zero diffraction order. Usual relief rainbow holograms or OVDs can form 3D effect, but at +1 or − 1 diffraction order only and they provide 3D parallax in left/right direction only, and after rotation/inclination of an element, a 3D image changes its color and further disappears completely. The new visual effect provides with full 3D parallax. Moreover, a 3D zero-order image is well visible when an optical element is rotated through 360 degrees; the color of 3D image does not depend on the viewing angle. A synthesis technology is developed incorporating the computation of scattering patterns in elementary areas, computation of the phase function of the entire optical element, and the formation of its microrelief by using e-beam lithography. The microrelief consists of multilevel kinoforms with an accuracy of 10 nm in terms of depth. It was demonstrated by experimental results that the new visual effect is easy for visual perception under white light illumination. A sample of nano-optical element is manufactured, which when illuminated by white light, forms a 3D image in the vicinity of zero-order of diffraction (video available at: https://bit.ly/3QtzxbI).