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

Highlights: • The formation of anatase phase only, whatever are Ni content and annealing duration. • Transmission and PL spectra redshifted with Ni content and annealing duration. • PL lowering with Ni content is due to the recombination rate of electron–hole reduction. • Annealing duration increases the recombination rate and then the PL intensity rises. • Increasing Ni content improves waveguiding properties and then two TE modes appear. - Abstract: 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