Shapeshifting Diffractive Optical Devices

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. Planar optical elements with theory‐matching efficiency and practical uses are realized in single step structuration of a photosensitive polymer surface by projecting holographic grayscale light patterns. Complete all‐optical reconfiguration of the surface is used to repeatedly morph previously fabricated optical elements in new ones with completely different optical functionalities, realizing reconfigurable on‐demand diffractive devices directly in the optical path.