Enhanced ultrafast infrared spectroscopy using coupled nanoantenna arrays

Kusa, Fumiya; Morichika, Ikki; Takegami, Akinobu; Ashihara, Satoshi

doi:10.1364/oe.25.012896

Cited by 23 publications

(19 citation statements)

References 21 publications

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“…In the traditional linear SEIRA experiments, the signal scales as a second power of the enhanced electric field . In order to get more insight into the mechanism of plasmon–molecule interaction, we use third-order nonlinear spectroscopy, where the signal scales as the fourth power of the field. − Combining the results of linear absorption, third-order femtosecond transient absorption, two-dimensional infrared heterodyned spectroscopy (2DIR), and theoretical analysis, we show that even though locally the plasmon fields are appreciably enhanced, the strength of the near-field coupling is not sufficient to explain the magnitude of the experimentally observed signals in samples with thick polymer films, which we found is caused by the radiation damping interaction. ,, Consequently, we identified that the surface-enhanced signal in samples with a film thickness of only a few nanometers can be dominated by the radiation damping mechanism, especially when strong vibrational chromophores are involved.…”

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confidence: 99%

Radiative Enhancement of Linear and Third-Order Vibrational Excitations by an Array of Infrared Plasmonic Antennas

et al. 2018

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Infrared gold antennas localize enhanced near fields close to the metal surface, when excited at the frequency of their plasmon resonance, and amplify vibrational signals from the nearby molecules. We study the dependence of the signal enhancement on the thickness of a polymer film containing vibrational chromophores, deposited on the antenna array, using linear (FTIR) and third-order femtosecond vibrational spectroscopy (transient absorption and 2DIR). Our results show that for a film thickness beyond only a few nanometers the near-field interaction is not sufficient to account for the magnitude of the observed signal, which nevertheless has a clear Fano line shape, suggesting a radiative origin of the molecule-plasmon interaction. The mutual radiative damping of plasmonic and molecular transitions leads to the spectroscopic signal of a molecular vibrational excitation to be enhanced by up to a factor of 50 in the case of linear spectroscopy and over 2000 in the case of third-order spectroscopy. A qualitative explanation for the observed effect is given by the extended coupled oscillators model, which takes into account both near-field and radiative interactions between the plasmonic and molecular transitions.

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Radiative Enhancement of Linear and Third-Order Vibrational Excitations by an Array of Infrared Plasmonic Antennas

et al. 2018

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“…41 In the case of the antenna arrays, additional control over the resonant wavelength can be achieved by tuning the strength of the near-neighbor interaction in the antenna axis (longitudinal) direction. 51,52,54 Stronger coupling, obtained for shorter distances between the adjacent antennas (a smaller longitudinal period of the array, Λ l ), red-shifts the wavelength of the resulting "pseudo-local" resonance, λ ̃loc .…”

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Infrared Open Cavities for Strong Vibrational Coupling

Cohn

Das

Basu

et al. 2021

J. Phys. Chem. Lett.

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Arrays of subwavelength plasmonic nanoparticles exhibiting narrowband lattice resonances are referred to as open cavities because of their ability to strongly couple with electronic excitations in molecular chromophores. However, realization of these ideas in the mid-infrared spectral region has been limited. We demonstrated a dramatic reduction in the bandwidth of lattice resonances in large-area arrays of half-wavelength mid-infrared antennas, reaching resonance quality factors above 200. By tuning the wavelength of the antenna-lattice resonances (ALR) to match the transition frequency of the molecular vibrational modes, we achieved a strong coupling between the ALR and the carbonyl stretching excitation in a thin film of (poly)methyl methacrylate (PMMA) polymer deposited on the array. Splitting of the polaritonic transitions, reduction of their bandwidth below that of the bare molecular transition, and characteristic dispersion confirmed the strong coupling regime. Our results pave the way for exciting research on the many-body correlated dynamics of vibrational polaritons.

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“…Because of strong light–matter coupling, SPhPs exhibit a reduced phase and group velocities and, therefore, bring about a subwavelength localization and an electric-field enhancement, respectively. These properties make SPhPs promising for nanophotonic applications in the mid-IR range, − such as surface-enhanced spectroscopy, − thermal radiation control, , and strong-field phenomena. , To date, the linear properties of SPhPs, namely, the dispersion relation, have been intensively studied. − …”

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Nonlinear Shift in Phonon-Polariton Dispersion on a SiC Surface

et al. 2020

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A nonlinear shift in the dispersion relation of a surface phonon-polariton (SPhP) is observed with grating-coupled pump–probe reflection spectroscopy. Upon excitation of an SPhP on a 4H-SiC surface, an instantaneous frequency shift of the SPhP mode at a constant wavevector is observed. This pump-induced frequency shift is equivalent to a nonlinear dispersion shift and to a Kerr-like nonlinear phase shift. The effective nonlinear index is evaluated to be orders of magnitude larger than the typical values of nonresonant dielectric responses. A nonlinear forced oscillator model aided by the first-principles calculations reproduce our observation and, furthermore, indicates that the primary origin is either the Born effective charge or the phonon anharmonicity depending on the frequency within the Reststrahlen band. The instantaneous shift is followed by a picosecond recovery, reflecting the energy relaxation and dissipation of the excited SPhP. This observed nonlinearity forms the basis of the self-phase modulation and four-wave mixing of SPhPs and paves the way toward nonlinear phonon-polaritonics.

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Enhanced ultrafast infrared spectroscopy using coupled nanoantenna arrays

Cited by 23 publications

References 21 publications

Radiative Enhancement of Linear and Third-Order Vibrational Excitations by an Array of Infrared Plasmonic Antennas

Radiative Enhancement of Linear and Third-Order Vibrational Excitations by an Array of Infrared Plasmonic Antennas

Infrared Open Cavities for Strong Vibrational Coupling

Nonlinear Shift in Phonon-Polariton Dispersion on a SiC Surface

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