A method for producing special supramolecular assemblies of colorants, in particular cyanine dyes, called J aggregates consists in depositing a monolayer of dendrimers on a support and subsequently in deposing cyanines in solution for forming the organized monolayer of J aggregates. The method can be used for producing a secondary light source for injecting light into a waveguide from a light energy received from a primary light source emitting at different wavelength. The secondary source, which consists of the J aggregates incorporating energy acceptors, can also be integrated into an optical device incorporating the waveguide.