Photochemical Mapping of the Multimodal Plasmonic Response of 2D Gold Crystals

The properties of hybrid plasmonic structures comprising a molecular ultrathin film of photoactive azobenzene derivatives and individual mesoscopic crystalline gold platelets are studied upon monochromatic irradiation. The spatial variation of the optical near-field produced by the excitation of high-order plasmon modes induces a net modification of the film corrugation with subwavelength pattern features. Unlike previous reports exploiting azo dye-grafted polymers, the photomigration of neat films composed of glass-forming push–pull azo compounds yields a highly resolved negative imprint of the local electric field intensity variations able to discriminate the different plasmon resonances sustained in these multimodal triangular prisms. Our experiments are in full agreement with green dyadic method simulations of near-field intensity maps and constitute both an efficient imaging technique and a way to self-align patterns of an optically active molecular medium in registry with the optical hotspots, which could be a major asset for the integration of filtering or gain media near plasmon-enhanced devices.