NOVELTY - The process comprises depositing optical convergent elements (16), transverse to a light beam (14), on a surface (2A) of a substrate (2), and applying the light beam on a portion of the substrate so as to form a cavity. The optical convergent elements have dimensions (10 nm to 100 mu m) that are less than a width of the light beam such that the light beam is applied on the substrate through the convergent elements, spherical shaped particles and cylindrical shaped sticks whose side walls are disposed against the surface of the substrate intended to be placed opposite to the light beam.    USE - The process is useful for optically structuring a substrate using laser ablation and photolithography techniques, where the structured substrate is useful for: photonic crystals; nanopores for the production of artificial kidneys filtration wafer; nanopores in the energy sector such as fuel cells; nanopores for recycling or treatment of water; and nanopores for filtering of waste gas.    ADVANTAGE - The process is capable of simply, rapidly and completely structuring the large area substrate.    DETAILED DESCRIPTION - The process comprises depositing optical convergent elements (16), transverse to a light beam (14), on a surface (2A) of a substrate (2), and applying the light beam on a portion of the substrate so as to form a cavity. The optical convergent elements: have dimensions (10 nm to 100 mu m) that are less than a width of the light beam such that the light beam is applied on the substrate through the convergent elements, spherical shaped particles and cylindrical shaped sticks whose side walls are disposed against the surface of the substrate intended to be placed opposite to the light beam; are disposed in a single layer; are disposed between the substrate and a support partially transparent to the wavelength of the light beam; and are removed by the light beam. The light beam is produced by a laser, and scans the substrate at the portion of the substrate covered by the optical convergent elements. The method further comprises interposing a converging lens between the laser and the optical convergent elements. An INDEPENDENT CLAIM is included for a device for structuring a substrate.    DESCRIPTION OF DRAWING(S) - The diagram shows a schematic view of a device for structuring a substrate.    Substrate (2)    Surface of the substrate (2A)    Structuration device (11)    Light source (13)    Light beam (14)    Optical convergent elements. (16)