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Electrochemical Modulation of Strong Vibration–Cavity Coupling

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journal contribution
posted on 31.12.2019, 16:20 by J. J. Pietron, K. P. Fears, J. C. Owrutsky, B. S. Simpkins
Modulation of strong coupling has implications for on-demand reactivity, optical modulation devices, and greater understanding of molecule–cavity coupling effects. Here, we electrochemically switch the redox couple benzoquinone/dihydroquinone (BQ/dHQ) within an optical cavity. We find that the BQ carbonyl species can be reduced, under appropriate biases, resulting in the complete elimination of the Rabi splitting, which is the signature of strong coupling. We achieve optical signal modulation of ∼100% at frequencies near the fundamental BQ carbonyl absorption as well as the polariton bands, and we experimentally evaluate the switching rate of such systems, finding that repeated cycling degrades performance, likely due to compositional changes in the electrochemical medium during the electrochemical reactions. Cavity resonances shift in correlation with the change of the solvent dielectric constant during electrochemical cycling. Although this consequent detuning influences the magnitude of optical modulation at the fundamental BQ resonance frequency, it makes optical modulation possible at many frequencies simultaneously since cavity fringe position scales with the refractive index. These results expand the understanding and utility of strong vibrational–cavity coupling and may lead to demonstrations of modified electrochemical response for technologically relevant material systems.