Nanoscale Photonic Barcodes Based on Anodic Alumina Photonic Crystal Heterostructures: Implications for Optical Communications, Data Storage, and Sensing

Photonic crystal heterostructures (PhCHs) have emerged as a promising tool to control light propagation with high precision. Anodization techniques are widely used to prepare PhCHs based on porous silicon and valve metal oxides. These techniques rely on oscillating anodization voltage or current to modulate the effective refractive index along the normal to the porous film surface, thereby creating photonic band gaps (PBGs) in PhCHs. However, anodization regimes described in the literature lack direct control over the optical path length (L) of prepared photonic structures, which is essential for fine-tuning the optical properties of PhCHs. In this work we present an anodization method for the preparation of PhCHs based on anodic aluminum oxide (AAO). The proposed anodizing regime accounts for chromatic dispersion of the refractive index and dispersion of L of the porous AAO film, providing direct control over the L of the prepared PhCHs. The potential of this approach was demonstrated by preparing PhCHs with up to 21 PBGs in the wavelength range from 250 to 1050 nm. Furthermore, we showcase a promising practical application of PhCHs by encoding 10-letter words and storing 47 bits of data using AAO photonic barcodes. The developed anodizing approach opens up avenues for designing and fabricating PhCHs with enhanced optical properties and potential applications in optical communication, data storage, and sensing.