Abstract: A method is for forming three-dimensional micro- and nanostructures, based on the structuring of a body of material by a mould having an impression area which reproduces the three-dimensional structure in negative form. This method includes providing a mould having a substrate of a material which can undergo isotropic chemical etching, in which the impression area is to be formed. An etching pattern is defined on (in) the substrate, having etching areas having zero-, uni- or bidimensional extension, which can be reached by an etching agent. A process of isotropic chemical etching of the substrate from the etching areas is carried out for a corresponding predetermined time, so as to produce cavities which in combination make up the impression area. The method is advantageously used in the fabrication of sets of microlenses with a convex three-dimensional structure, of the refractive or hybrid refractive/diffractive type, for forming images on different focal planes.

Abstract: What is described is a lithographic method for fabricating three-dimensional structures on the micrometric and submicro-metric scale, including the operations of: depositing a layer of a first resist on a substrate; depositing a layer of a second resist on the layer of the first resist; forming a pattern of the second resist by lithography; depositing a further layer of the first resist on the previous layers; and forming a pattern of the first resist by lithography. The second resist is sensitive to exposure to charged particles or to electromagnetic radiation in a different way from the first; in other words, it is transparent to the particles or to the electromagnetic radiation to which the first resist is sensitive, and therefore the processes of exposure and development of the two resists are mutually incompatible to the extent that the exposure and development of one does not interfere with the exposure and development of the other.

Abstract: A silicon-based light-emitting device is described and comprises an active region, an excitation system which can bring about a condition of inversion of the population of carriers within the active region, and semi-reflective elements which can define a resonant optical structure in which the active region is inserted so as to bring about stimulated emission of coherent light. The active region comprises silicon nanostructures immersed in a silicon-dioxide-based dielectric matrix.