A process for manufacturing an electroluminescent device comprising the steps of: making an organic or inorganic templating frame, comprising monodispersed nanoelements, in particular nanospheres; providing said nanoelements with a sheath consisting of metal nanoparticles, each nanoelement with its sheath of metal nanoparticles forming a core shell. The core shells are assembled together so as to make the three-dimensional percolated layer, having cavities whose size is around wavelength.