Patent ID: 8029887

Claim:
An optical article having periodic microstructure comprising pure silicon oxide, optionally modified by the addition of one or more oxides of elements other than silicon, having essentially complete isotropy and dimensions of the periodic microstructure are equal to or lower than 500 μm, where the article is made by a process comprising, a) preparing at least one original high precision mould having an average roughness lower than 20 nm; b) reproducing, in a silicone rubber, one or more imprints, having the same size and a reversed symmetry with respect to said mould; c) preparing by the employment of one or more of the moulds obtained in step a) or imprint obtained in step b) an optical article having reduced dimensions and reversed symmetry with respect to the starting mould/imprint; according to a sol-gel procedure, in which the sol-gel procedure comprises a preliminary step of filling said mould in a cool state with a sol containing pure silicon oxide precursors, gelling the sol, drying the sol to form a dried gel, removing the dried gel from the mould and miniaturizing the dried gel to form an optical article, d) preparing from the so obtained optical article a further optical article again having reduced sizes and reversed symmetry, or of imprints according to step b); e) repeating steps c)-d), each repetition results in successively smaller microstructure dimensions by a factor of two until a desired miniaturized dimension is achieved.