Porosity tuning of the optical properties of mesoporous silica planar defect in macroporous silica opal

Periodic mesoporous silica films were embedded between photonic crystals to form defect-based monolithic structures capable of post-growth tuning. Tetramethyl orthosilicate was infiltrated into monolithic structures in order to form silica layers in their void spaces, resulting in changes to the optical spectra. With the increase in the number of infiltration cycles, the optical signatures of the defect-based monolithic structures red-shift, caused mainly by the increase in the effective index of refraction of the entire structure. Furthermore, the red-shift of the optical signatures in monolithic structures deviates when compared to the net-effect of infiltration on stand-alone structures of periodic mesoporous silica films and photonic crystals. Simulations based on scalar wave approximation corroborate the results obtained by ellipsometry, UV-VIS spectroscopy, scanning electron microscopy, and x-ray diffraction experiments.