Angular Photothermal Depletion of Randomly Oriented Gold Nanorods for Polarization-Controlled Multilayered Optical Storage

Increasing the number of layers used in optical data storage media is a promising technique to address increasing capacity demands. However, heavy optical losses are experienced by light on transit through multilayered optical recording media, requiring prohibitively high readout powers for deep layers. Here, gold nanorods are used as the optical data storage medium, and the polarization response of their surface plasmon resonance is exploited to control the optical extinction imposed by the nanorods. A polarization response is imposed onto the initially randomly oriented nanorod films by photothermal depletion technique. The influence of increasing the depletion fluence on the polarization response of nanorod films is investigated. This technique is extended into multilayer films, imposing alignment through 12-layer nanorod films. Successful optical patterning is carried out on each of the layers following depletion, with a 20x decrease observed in the readout power required to resolve a pattern from layer 12. The proposed angular depletion method will be highly beneficial in reducing optical losses multilayered optical storage applications, enabling storage capacities to be efficiently increased, as well as applications using a continuous medium with high concentrations of plasmonic nanoparticles, where optical losses are significant.