The effect of the voltage waveform on the microstructure and optical properties of porous anodic alumina photonic crystals

Abstract Porous anodic alumina photonic crystals (PAA-PhCs) with brilliant colours were successfully fabricated by pulse anodization of aluminium in an oxalic acid electrolyte. The influence of the voltage waveform on the microstructure of the PAA-PhCs was investigated by adjusting the anodization period, anodization amplitude, and anodization offset. Here, we report a simplified method for compensation of the photonic band gap (PBG) drift using AC waveforms instead of the periodic length-controlled method. Scanning electron microscopy (SEM) results showed that the layer thickness of the PAA-PhC prepared by an AC pulse was gradually reduced from 360 nm to 290 nm, which was completely different from a previous report showing that the layer thickness of a sample prepared by a DC pulse remained unchanged. In addition, the effect of chemical corrosion in a phosphoric acid solution on the microstructures of the PAA-PhCs was analysed by comparative experiments. PBG drift caused by minor defects in the nanostructure during the anodization process could also be compensated for by adjusting the anodizing time and corrosion time. Our approach may help to broaden the potential applications of and provide important guidance for photonic crystal display and new devices.