Tuning the optical properties of nanoporous anodic alumina photonic crystals by control of allowed voltage range via mixed acid concentration

This study investigates the tunable fabrication of photonic crystals (PCs) based on nanoporous anodic alumina (NAA) templates through modification of nanopore diameter, affecting the PCs optical response. This was realized by controlling phosphoric acid concentration (C-ph) and anodization current density. This approach along with chemical etching offers the opportunity to adjust optical band gap in a wide range of wavelengths (from about 400 to 1100 nm). To this end, the effect of C-ph, on current density and threshold voltage was investigated. To analyze formation mechanism of resulting multilayers and optimize their optical characteristics, the potential ratio, span, cycles and charge density were examined, thereby providing a band gap as narrow as 6 nm. The sensing analysis revealed that the modified multilayer shows enhanced sensitivity to the changes of effective media inside the nanopores. These findings provide insights into the development of both optical sensors and optoelectronic nanodevices based on the NAA-based PCs.