Covert Photonic Barcodes Based on Light Controlled Acidichromism in Organic Dye Doped Whispering‐Gallery‐Mode Microdisks

Photonic barcodes with a small footprint have demonstrated a great value for multiplexed high‐throughput bioassays and tracking systems. Attempts to develop coding technology tend to focus on the generation of featured barcodes both with high coding capacity and accurate recognition. In this work, a strategy to design photonic barcodes is proposed based on whispering‐gallery‐mode (WGM) modulations in dye‐doped microdisk resonant cavities, where each modulated photoluminescence spectrum constitutes the fingerprint of a corresponding microdisk. The WGM‐based barcodes can achieve infinite encoding capacity through tuning the dimensions of the microdisks. These photonic barcodes can be well disguised and decoded based on the light controlled proton release and acidichromism of the organic materials, which are essential to fulfill the functions of anti‐counterfeiting, information security, and so on. The results will pave an avenue to new types of flexible WGM‐based components for optical data recording and security labels.