Photoluminescence in Er(3+)/Yb(3+)-doped silica-titania inverse opal structures RID D-1745-2009

Er(3+) photoluminescence (PL) and Yb(3+) -> Er(3+) energy transfer (ET) phenomena in the near infrared (NIR) have been studied in three-dimensional (3-D) inverse opal (IO) structures synthesized by a colloidal/sol-gel route, starting with the deposition of polystyrene microsphere (235 nm and 460 nm diameter) direct opal templates by convective self-assembly, followed by infiltration of the interstices with Er(3+)/Yb(3+)-doped silica, titania and silica-titania sols and heat-removal of the polymeric template material. The crystalline quality of the IOs has been optimized through suitable substrate treatments, plus the control of temperature and humidity during deposition of the templates. The structural and optical properties of the 3-D opal and IO structures have been studied by field emission scanning electron microscopy and visible-NIR reflection spectroscopy, in order to assess the relationship between microstructure and the photonic properties obtained. Photonic bandgaps have been evidenced by the corresponding stop bands in the reflection spectra. The shape and the intensity of the Er(3+) (4)I(13/2) -> (4)I(15/2) transition at similar to 1.5 mu m were modified in most IOs relatively to similar matrix deposits without a photonic crystal structure, particularly in the case of pure silica and titania IOs, where the PL peak narrowed and intensified. It was not possible at this stage to detect Yb(3+) -> Er(3+) ET phenomena in the IOs structures.