In optical devices like diffraction gratings and Fresnel lenses, light wavefront is engineered through the structuring of device surface morphology, within thicknesses comparable to the light wavelength. Fabrication of such diffractive optical elements involves highly accurate multistep lithographic processes that in fact set into stone both the surface morphology and optical functionality, resulting in intrinsically static devices. In this work, this fundamental limitation is overcome by introducing shapeshifting diffractive optical elements directly written on an erasable photoresponsive material, whose morphology can be changed in real time to provide different on‐demand optical functionalities. First a lithographic configuration that allows writing/erasing cycles of aligned optical elements directly in the light path is developed. Then, the realization of complex diffractive gratings with arbitrary combinations of grating vectors is shown. Finally, a shapeshifting diffractive lens that is reconfigured in the light‐path in order to change the imaging parameters of an optical system is demonstrated. The approach leapfrogs the state‐of‐the‐art realization of optical Fourier surfaces by adding on‐demand reconfiguration to the potential use in emerging areas in photonics, like transformation and planar optics.

The diffraction of polychromatic light from periodic superficial structures is often responsible for the structural colors observed in Nature. Similarly, engineered microtextures fabricated on metallic or dielectric surfaces can be used to design diffracted optical patterns with desired shapes and colors. To this aim, advanced diffraction gratings with exceptional design and functionality are continuously proposed, and new fabrication methods follow to stay abreast with the improving design capabilities. Multiplexed surface reliefs, acting as complex gratings with tunable diffraction behavior, can be readily produced on films of azobenzene containing materials by exposing the surface to controlled sequences of holographic interference patterns. This work fully investigates, both theoretically and experimentally, the use of light‐induced surface relief on azopolymers for the realization of large‐scale multiplexed gratings with optimized diffraction performances. The reconfigurable diffraction gratings able to diffract polychromatic light in the same direction with controllable relative color intensities by tuning exposure parameters in a switchable two‐beam interference setup are designed and fabricated. The results can be generalized to more complex diffractive devices, usable in emerging display application areas.

Holographic relief gratings can be fabricated directly on the surface of azobenzene-containing materials (or simply azomaterials) without additional development steps. Despite often being described to have ideal sinusoidal profiles, the developing surface morphology in large amplitude gratings can affect the light distribution of the writing interferogram, causing profile deformations and deviations in the expected diffraction behavior. In this work, we characterize the temporal evolution of the surface relief grating (SRG) morphology fabricated by means of interference lithography on azopolymer films, quantitatively relating the results of a Fourier analysis of their surface profiles to the accurate measurement of efficiencies in the transmitted diffraction orders. A reliable surface structuration dynamics is empirically extracted from the analysis and used to formulate a simple but detailed diffraction model that, within the scalar diffraction theory, exhaustively describes the diffraction behavior of real SRGs without the need of complex rigorous electromagnetic theories. Our results add a deeper insight in the quantitative description of the morphology and the diffraction behavior of SRGs, which can contribute to their adoption for operating high-performance, reconfigurable, compact, and lightweight diffractive optical devices.

Holographic technologies have been envisioned as potentially impacting many areas of everyday life, including science, entertainment, and healthcare, but their adoption is still at an early stage. Recent achievements in flat optics research gave an unprecedented strength to this field, proposing holographic devices as light‐modulating structured surfaces at micro and nanoscale. However, these components are typically static, requiring demanding, burdensome, and irreversible lithographic processes. Here a maskless lithographic framework is reported which only uses light irradiation to fabricate reprogrammable diffractive holographic projectors directly on the surface of a dielectric photomorphable polymer film. Lithographic and characterization optical schemes are combined to optimize in real‐time the light‐modulating performances of the surface, producing holograms with enhanced efficiency. Reprogrammable holograms are then demonstrated to change shape and position according to dynamical optical remorphing of the surface, realizing a proof‐of‐concept of a pixel‐less morphological projector. The approach opens new routes for holographic image displaying and dynamic optical data encoding and sharing.

SRG inscription on azopolymers films is strongly enhanced by constrained azobenzene–chain interaction established through double H-bond supramolecular synthon. Selective removal of azobenzene from patterned samples is possible by solvent rinse.

Microstructures with diverse and individualized morphologies are achieved by computer generated holography to reconfigure azopolymer micropillars in three dimensions.