Spatially Resolved Organic Whispering-Gallery-Mode Hetero-Microrings for High-Security Photonic Barcodes.

Whispering-gallery-mode (WGM) microcavities featuring distinguishable sharp peaks in a broadband exhibit enormous advantages in the field of miniaturized photonic barcodes. However, such kind of barcodes developed hitherto are primarily based on microcavities wherein multiple gain medias were blended into a single matrix, thus resulting in the limited and indistinguishable coding elements. Here, a surface tension assisted heterogeneous assembly strategy is proposed to construct the spatially resolved WGM hetero-microrings with multiple spatial colors along its circular direction. Through precisely regulating the charge-transfer (CT) strength, full-color microrings covering the entire visible range were effectively acquired, which exhibit a series of sharp and recognizable peaks and allow for the effective construction of high-quality photonic barcodes. Notably, the spatially resolved WGM hetero-microrings with multiple coding elements were finally acquired through heterogeneous nucleation and growth controlled by the directional diffusion between the hetero-emulsion droplets, thus remarkably promoting the security strength and coding capacity of the barcodes. The results would be useful to fabricate new types of organic hierarchical hybrid WGM heterostructures for optical information recording and security labels.