Abstract: A method for manufacturing an optical metasurface is configured to operate in a given working spectral band. The method comprises: obtaining a 2D array of patterns, each comprising one or more nanostructures forming dielectric elements that are resonant in said working spectral band, said nanostructures being formed in at least one photosensitive dielectric medium; exposing said 2D array to a writing electromagnetic wave having at least one wavelength in said photosensitivity spectral band, said writing wave having a spatial energy distribution in a plane of the 2D array that is a function of an intended phase profile, so that each pattern of the 2D array produces on an incident electromagnetic wave having a wavelength in the working spectral band, a phase variation corresponding to a refractive index variation experienced by said pattern during said exposure.

Abstract: The invention describes a device allowing the observation of a sample, comprising particles, for example biological particles, by lensless imaging. The sample is disposed against a substrate, the substrate being interposed between a light source and an image sensor. The substrate comprises at least one thin film, extending across a thin film plane, structured so as to form a diffraction grating, designed to confine a part of a light wave emitted by the light source, in a plane parallel to said thin film plane. The device does not comprise magnification optics between the substrate and the image sensor.