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

• 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.

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.

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