Randomly Distributed Plasmonic Hot Spots for Multilevel Optical Storage

Multilevel optical storage is regarded as one efficient way to achieve higher capacity. In this paper, a kind of multilevel optical storage is presented by encoding the plasmonic hot spots among coupling gold nanorods (GNRs). The hot spots not only lower the recoding energy, but enhance two-photon-induced luminescence (TPL) intensity of the GNRs adjacent to hot spots significantly. From the numerical simulations based on finite-difference time-domain technique, it can be seen that the existence of hot spots expands the range of TPL intensity and makes a steeper function of TPL intensity distribution than isolated GNRs. The multilevel optical storage is performed experimentally in the GNR–poly­(vinyl alcohol) (PVA) films with optical density (OD) = 3, 12, and 24. The six-level optical storage with high quality could be fulfilled with ultralow energy of only a few picojoule per pulse in the GNR–PVA films of OD = 12. This work can be the building blocks for the cold data storage in Big Data era.