Switchable narrow nonlocal conducting polymer plasmonics

Dynamically switchable surface plasmons in conducting polymers constitute an emerging route towards intelligent metasurfaces, but polymer plasmons have so far suffered from weak resonances with low quality factors (Q < 1-2). Here, we address this by nonlocal coupling of individual poly(3,4-ethylenedioxythiophene) (PEDOT) nanoantennas through collective lattice resonances (CLR) in periodic arrays (with resonance wavelengths around 2.0-4.5 μm). The results show that careful tuning of CLR matching conditions enables organic plasmonic resonances with Q up to 12. Angle-dependent extinction spectra connect the results to the enhancement of radiative coupling from diffractive lattice effects. Furthermore, the nonlocal coupling strength between nanoantenna units and lattice could be modulated via redox reactions, enabling the narrow CLRs to be reversibly switched with large modulation depth (between 7% and 45% extinction). By improving resonance strength and Q, the study circumvents previous limitations of conducting polymer plasmonics and shows feasibility for practical applications in active metasurfaces and nano-optics.