Fabrication of Er3+ active silica direct and inverse opals with high quantum efficiency

Er
³⁺
active 3D photonic crystal in direct and inverse opal configuration were realized, on silica substrate, by sol-gel routes. The optical properties were investigated by means reflectance measurements at different incidence angles. From optical measurements it's evident that both structures (direct and inverse opals) exhibited a pseudo photonic band gap in the visible range. In fact a reflective visible light could be easily observed by the naked eye due to optical Bragg diffraction from the crystal planes.