Active Tuning with Photochromic Molecules Coupled to Plasmonic Nanoantennas

Plasmonic nanostructures with actively tunable resonances promise to enable smart materials with multiple functionalities, on-chip spectral-based imaging and dynamically reconfigurable optoelectronic devices. A variety of tunable materials have been integrated with plasmonic structures, however, the tuning range in the visible regime has been limited to less than the linewidth of the resonance resulting in small on/off ratios. Here we demonstrate dynamic, reversible tuning of plasmon resonances up to 71 nm in the visible regime by incorporating photochromic molecules into plasmonic nanopatch antennas. Ultraviolet light is used to switch between two isomers with different refractive indices demonstrating a tuning figure of merit of 1.43, defined as the ratio between the tuning range and the linewidth of the resonance. Moreover, the effect of the dispersion on the tuning range is elucidated by studying over 40 individual nanoantennas with fundamental resonances from 550 to 720 nm, revealing good agreement with finite-element simulations.