We report the realization and characterization of porous nanostructures where a periodic refractive index modulation is
achieved by stacking layers with different nano-architectures. One multilayer photonic crystal has been fabricated
starting from colloidal dispersion of silicon dioxide and zirconium dioxide using spin coating technique. Improved
efficiency of Bragg reflectivity (up to 85%) has been obtained by a new bottom-up fabrication technique of photonic
hierarchical nanostructures based on self-assembly from the gas-phase at low temperature whit a very thin (≈ 1 μm)
photonic crystal devices. Due to the high porosity, these systems can be infiltrated with nematic liquid crystals leading to
tuning of the Bragg reflection band by applying low voltages to the structure.