Nina A. Sapoletova

The slowing down of the group velocity of light at the edges of the photonic band gap is one of the important optical effects observed in photonic crystals. The “slow light” effect is used in photocatalysis to enhance the photocatalytic activity of semiconductors. In this work, anatase photonic crystals with different spectral positions of the photonic band gap (390–1283 nm, measured in water) were obtained. It has been shown that the maximum photocatalytic activity in the photodegradation of methylene blue is exhibited by photonic crystals with the position of one of the photonic band gaps near the intrinsic absorption edge of the semiconductor (410 nm). At the same time, the photocatalytic activity of an anatase photonic crystal increases by 30% when the photonic band gap of the third rather than the first order is located near the absorption edge of the semiconductor.

One-dimensional photonic crystals (1D PhCs) obtained by aluminium anodizing under oscillating conditions are promising materials with structure-dependent optical properties. Electrolytes based on sulphuric, oxalic, and selenic acids have been utilized for the preparation of anodic aluminium oxide (AAO) 1D PhCs with sub-100-nm pore diameter. AAO films with larger pores can be obtained by anodizing in phosphorous acid at high voltages. Here, for the first time, anodizing in phosphorous acid is applied for the preparation of AAO 1D PhCs with nonbranched macropores. The sine wave profile of anodizing voltage in the 135–165 V range produces straight pores, whose diameter is above 100 nm and alternates periodically in size. The pore diameter modulation period linearly increases with the charge density by a factor of 599 ± 15 nm·cm²·C⁻¹. The position of the photonic band gap is controlled precisely in the 0.63–1.96 µm range, and the effective refractive index of AAO 1D PhCs is 1.58 ± 0.05.

Anodic titanium oxide is a promising material for the formation of photonic crystal structures due to its high refractive index, stability in acidic media, and semiconductor conductivity. One-dimensional photonic crystals are obtained by the anodization of titanium with triangle wave modulation of the voltage versus the charge density. The dependence of the position of the photonic band gap on the charge density per anodizing cycle is studied. The reflection coefficient within the photonic band gap of the obtained samples reaches 70%. Taking into account chemical dissolution of the pore walls during anodic oxidation and gradual reduction of the structure period along the film thickness make it possible to obtain photonic crystals based on titanium oxide with a record value of the Q factor of 9.6.