Holographic fabrication of reconfigurable diffractive elements

¹ Physics Department “E. Pancini”, University of Naples Federico II, Complesso Universitario di Monte Sant’Angelo, via Cinthia 21, 80126, Naples
² Department of Chemical Sciences, University of Naples Federico II, Complesso Universitario di Monte Sant’Angelo, Via Cintia, 80126 Naples

^* Corresponding author: stefanoluigi.oscurato@unina.it

Published online: 31 October 2024

Abstract

The fabrication of Diffractive Optical Elements (DOEs) involves the analog patterning of material surfaces on the scale of light wavelength. This typically requires multi-step lithographic processes. Differently from the photoresists of standard lithography, thin films of amorphous azobenzene-containing polymers (azopolymers) can directly produce a structured surface using a single irradiation step with structured light. The resulting surface reliefs can be used directly as planar phase-modulating DOEs without the need for any post-exposure process. Additionally, the surface geometry and its optical functionality can be reconfigured at will. Here, we demonstrate reprogrammable and ready-to-use azopolymer diffractive gratings, lenses, and holographic projectors, produced by grayscale digital holographic patterns. By exploiting the all-optical scheme based of computer-generated holography, the diffraction behavior of the DOEs is optimized during the developing of structured surfaces. Full all-optical reconfigurability of the fabricated devices is also achieved. Our approach provides a versatile, efficient, and all-optical reversible fabrication framework for DOEs, making it a promising option to overcome the demanding, cumbersome, and irreversible fabrication processes typically involved in the realization of planar diffractive optical devices.