Optical security components, manufacture of such components and secure objects provided with such components

A method for manufacturing an optical security component for securing an object, for example a valuable document, for example an identity document or a banknote, the method comprising:

• depositing a first layer of dielectric material, transparent in the visible spectrum, onto a support film;
• forming at least a first diffractive structure on said first layer;
• depositing a second layer at least partially covering said first diffractive structure, and having a reflection spectral band in the visible spectrum, and wherein:
• said first diffractive structure consists of a set of optical elements adjacent to each other, each optical element having a maximum dimension of less than about 300 μm and comprising a microstructure modulated by a sub-wavelength diffraction grating with one or more pitches ranging between about 150 nm and about 400 nm, such that:
• said microstructure is configured to deflect an incident light beam and is substantially invariant by azimuthal rotation by an angle of less than 90°about a first axis substantially perpendicular to a plane of the component;
• said sub-wavelength diffraction grating is substantially invariant by azimuthal rotation by an angle of less than 90° about a second axis substantially coincident with said first axis and is configured to produce a colored effect after the second layer has been deposited.