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NM09.07.03 : Control of Vibration-Cavity Polaritons in the Frequency and Time Domains

8:30 AM–9:00 AM Apr 4, 2018

PCC North, 200 Level, Room 231 BC

Description
Blake Simpkins1 Adam Dunkelberger1 Kenan Fears1 Wonmi Ahn2 Igor Vurgaftman1 Jeff Owrutsky1

1, Naval Research Laboratory, Washington, District of Columbia, United States
2, National Research Council, Washington, District of Columbia, United States

We will focus on using light-matter interactions in an effort to alter the chemical behavior of a target molecular species. This is done through cavity coupling to a molecular vibration. Coupling vibrational transitions to resonant optical modes creates vibrational polaritons shifted from the uncoupled molecular resonances and provides a convenient way to modify the energetics of molecular vibrations and to explore controlling chemical reactivity[i] and energy relaxation.[ii] Here, we experimentally and numerically describe strong coupling between a Fabry-Pérot cavity and several molecular species (e.g., poly-methylmethacrylate, thiocyanate, hexamethyl diisocyanate)[iii] and investigate the transition from the strong to weak coupling regimes. Furthermore, we map the influence of molecule/cavity mode overlap by systematically altering the position of a molecular slab throughout the first and second order cavity resonances with results agreeing well with analytical and transfer matrix predictions.
In the time domain, we use pump-probe infrared spectroscopy to characterize the dynamics of vibration-cavity polaritons for the CO vibrational band of W(CO)6.2 At very early times, we observe quantum beating between the two polariton states, which may account for a lower degree of vibrational excitation observed. After the quantum beating, we interpret our observations as excited-state absorption from polariton modes and uncoupled reservoir modes. The polariton mode relaxes ten times more quickly than the uncoupled vibrational mode and it exhibits a cavity tuning-dependent lifetime which we believe is a result of modifying the relative fractions of cavity and molecular character comprising the polariton. We show that energy relaxation times depend on cavity-vibration coupling and thereby may be a viable way to control the frequency and lifetime of vibration-cavity polaritons and, therefore, may provide opportunities to influence chemical reactivity. This work points out the possibility of systematic and predictive modification of the excited-state kinetics of vibration-cavity polariton systems. Opening the field of polaritonic coupling to vibrational species promises to be a rich arena amenable to a wide variety of infrared-active bonds that can be studied in steady state and dynamically.


[i] A. Thomas, J. George, A. Shalabney, M. Dryzhakov, S. J. Varma, J. Moran, T. Chervy, X. Zhong, E. Devaux, C. Genet, J. A. Hutchison, T. W. Ebbesen, Angew. Chem. Int. Ed. Engl. (2016)

[ii] A.D. Dunkelberger, B.T. Spann, K.P. Fears, B.S. Simpkins, and J.C. Owrutsky, “Modified Relaxation Dynamics in Coupled Vibration-cavity Polaritons”, Nature Communications 7, 13504 (2016)

[iii] B. S. Simpkins, K. P. Fears, W. J. Dressick, B. T. Spann, A.D. Dunkelberger, and J. C. Owrutsky, , ACS Photonics, 2, 1460 (2015)

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