Three-Dimensional Photonic Crystals Based on Porous Anodic Aluminum Oxide.

Photonic crystals (PCs) consisting of a periodic arrangement of holes in dielectric media have found success in light manipulation and sensing. Among them, three-dimensional (3D) PCs are in high demand due to their unique properties originating from multiple photonic band gaps (PBGs) and even full ones. Here, 3D PCs based on porous anodic aluminum oxide (AAO) were fabricated for the first time.

New insight into anodization of aluminium with focused ion beam pre-patterning.

The self-ordered anodic aluminium oxide (AAO) structure consists of micron-scale domains-defect-free areas with a hexagonal arrangement of pores. A substantial increase in domain size is possible solely by pre-patterning the aluminium surface in the form of a defect-free hexagonal array of concaves, which guide the pore growth during subsequent anodization. Among the numerous pre-patterning techniques, direct etching by focused gallium ion beam (Ga FIB) allows the preparation of AAO with a custom-made geometry through precise control of the irradiation positions, beam energy, and ion dosage.

One-Dimensional Photonic Crystals with Nonbranched Pores Prepared via Phosphorous Acid Anodizing of Aluminium.

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.

Polarization-enhanced cell walls etching of anodic titanium oxide.

Anodic titanium oxide (ATO) photonic crystals (PhCs) are promising for photonics, photocatalysis, and solar cells. A refractive index modulation in ATO PhCs is caused by the modulation of porosity and, thus, the pore diameter should be controlled precisely. The ATO cell walls etching in electrolyte solution during anodizing increases the porosity of the PhC structure and shifts the photonic band gap (PBG) position to shorter wavelengths.

Titania Photonic Crystals with Precise Photonic Band Gap Position via Anodizing with Voltage versus Optical Path Length Modulation.

Photonic crystals based on titanium oxide are promising for optoelectronic applications, for example as components of solar cells and photodetectors. These materials attract great research attention because of the high refractive index of TiO. One of the promising routes to prepare photonic crystals based on titanium oxide is titanium anodizing at periodically changing voltage or current.