Structural, optical and waveguiding properties improvement of SiO2/TiO2 Bragg reflectors processed by the sol–gel method under the effect of Ni-doped TiO2 and annealing duration

We investigated the nickel doped TiO2 layer and annealing duration effects on SiO2/TiO2 Bragg reflectors. The films crystallize in pure anatase phase whatever is the Ni content and the annealing duration. In UV–vis-NIR analyses, variations of width, position and transmission coefficient of the stop-band were observed. The PL spectra red-shifted when the Ni content and annealing duration increased. As the annealing duration increases, an additional sharp emission peak appears around 867 nm, indicating a reduced number of defects. As Ni content increased, the M-lines spectroscopy shows two transverse electric polarization guided modes TE0 and TE1, which indicates a decreased refractive index and an increased film thickness.