Engineering Near-Field SEIRA Enhancements in Plasmonic Resonators

Published

January 20, 2016

Author(s)

Jungseok Chae, Basudev Lahiri, Andrea Centrone

Abstract

Engineering of the optical resonances in plasmonic resonators arrays is achieved by virtue of the intrinsic properties to the constituent structures such as composition, size and shape and by controlling the inter-resonator interactions by virtue the array geometrical arrangement. The nanoscale confinement of the plasmonic field enhances light-matter interactions enabling, for instance, the surface enhanced infrared absorption (SEIRA) effect. However, its subwavelength confinement also poses an experimental challenge for discriminating the response stemming from individual resonators and from the collective response in densely packed arrays. In this work, the photothermal induced resonance (PTIR) technique is leveraged to obtain nanoscale images and spectra of near-filed SEIRA hot spots observed in isolated plasmonic resonators of different shapes and for individual resonators within closely packed plasmonic arrays. Results are correlated with far-field spectra and theoretical calculations. In the case of isolated resonators, the asymmetric split ring provide a significantly stronger SEIRA enhancement with respect to U-shaped, C-shaped and crescent-shaped resonators characterized by similar resonant plasmonic wavelengths. For U-shaped resonators arranged in squared lattices of different pitches the SEIRA hot-spot intensity increases as a function of the pitch, suggesting that the inter-resonators interactions reduce the resonators’ intrinsic cross-section. However, in the far-filed, the higher resonator density of closely packed arrays overcompensate the reduction of the cross-section and provides a stronger average response. In contrast, for squared arrays composed by asymmetric split rings, the near-filed SEIRA enhancement benefits from the constructive hot-spot overlap in the most closely-packed arrays and results is a non-monotonic function of the pitch.

Citation

ACS Photonics

Volume

3

Issue

1

Pub Type

Journals

Download Paper

https://doi.org/10.1021/acsphotonics.5b00466

Keywords

Plasmonic materials, split ring resonators, surface enhanced infrared absorption, Photothermal Induced Resonance.

Citation

Chae, J. , Lahiri, B. and Centrone, A. (2016), Engineering Near-Field SEIRA Enhancements in Plasmonic Resonators, ACS Photonics, [online], https://doi.org/10.1021/acsphotonics.5b00466 (Accessed October 31, 2024)