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Journal Articles Journal of Applied Physics Year : 2022

Substrate-supported nano-objects with high vibrational quality factors

Aurélien Crut

Abstract

Recent optical time-resolved experiments on single supported nano-objects (gold nanodisks with various diameter over thickness ratios) have demonstrated a marked enhancement of their vibrational quality factors for specific nano-object morphologies, resulting from the near-suppression of radiative vibrational damping associated with the emission of acoustic waves in the nano-object environment. This paper clarifies the origin of this phenomenon, which is ascribed to the creation of a “quasi-bound state in the continuum” vibrational mode by radiative coupling between two nano-object modes whose frequencies become close for specific nano-object shapes. The symmetry breaking induced by the presence of a substrate, which limits nanodisk acoustic emission to a half-space, is shown to play an essential role in enabling such radiative coupling. The impact of the acoustic mismatch between the nano-object and the substrate is explored, and it is shown that a moderate acoustic mismatch can still enable the creation of near-localized vibrational modes with high radiative quality factors, while allowing radiative coupling effects to occur over a broad range of nano-object geometries. Although this paper focuses on the situation of a substrate-supported gold nanodisk, which has already been the object of experimental investigations, the effects that it describes are general and constitute a promising approach to enhance the vibrational quality factors of nano-objects.
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Dates and versions

hal-03725656 , version 1 (18-07-2022)

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Aurélien Crut. Substrate-supported nano-objects with high vibrational quality factors. Journal of Applied Physics, 2022, 131 (24), pp.244301. ⟨10.1063/5.0093585⟩. ⟨hal-03725656⟩
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