The fabrication of Diffractive Optical Elements (DOEs) involves the structuration of material surfaces with geometries on the scale of light wavelength. Differently to standard photoresists, thin films of amorphous azobenzene-containing polymers (azopolymers) directly develop surface reliefs in the irradiated area, directly usable as phase-modulating masks, acting as DOEs. Surface structuration is the result of an intrinsically reversible light-induced material displacement, which makes azopolymer films usable as photo-transformable planar diffractive optical devices. Here we demonstrate reprogrammable and ready-to-use diffractive gratings, lenses, and holographic projectors, directly obtained in a single photo-structuration step through the projection of a grayscale holographic pattern over the azopolymer film free surface. The all-optical scheme, based on the principles of computer-generated holography, allows a simple and accurate engineering of the light pattern used for the azopolymer surface structuration. Additionally, direct pattern transferring opens to the real-time optimization of the device allowing to test and prototype its diffraction properties right during the developing of structured surfaces. The proposed approach offers a versatile, efficient, and full-optical reversible fabrication framework for DOEs, making it a promising option to overcome the demanding, burdensome, and irreversible manufacturing processes typically involved in the realization of planar diffractive optical devices.
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