Absorptive Optical Filters and Polarizers through Multiplexing and Reshaping of Low-Polydispersity Plasmonic Nanorods.

Strong light-matter interactions and tunable optical cross-sections of gold nanorods (AuNRs) offer unique alternatives to traditional atomic- and molecular-base absorptive elements for filters and polarizers. However, harnessing these properties in a large area or bulk components remains a significant challenge, largely due to limited options for affordable fabrication of large quantities of AuNRs with narrow polydispersity. Herein, these challenges are overcome with the recent large-volume synthesis of highly uniform AuNRs, spectral hole burning, and thermoforming of polymer nanocomposites. By quantitatively assessing the impact of polydispersity, we design and formulate strategies for absorptive bandpass filters from the visible to the infrared with multiplexed populations of AuNRs with precise aspect ratios (ARs). Optical performance is tuned using spectral hole burning via pulsed laser irradiation, providing filters from stopbands to passbands with multiple notches. Integrating these methods with controlled nanorod alignment via thermoforming polymer nanocomposites, we demonstrate flexible sheet dichroic polarizers with multiple transmission bands using a range of plasmonic nanoparticles, as well as conformably encapsulating three-dimensional shapes with thermally controlled shape memory processes. Overall, this platform leverages the unique properties of plasmonic nanoparticles for large-area optical films, coatings, and components, with potential applications ranging from displays to environmental control and energy harvesting.