Paper on "Plasmonic enhancement of photoacoustic-induced reflection changes" in Spotlight on Optics

News - 24 September 2021 - Communication ImPhys

The paper, “Plasmonic enhancement of photoacoustic-induced reflection changes”, has been chosen for inclusion in “Spotlight on Optics” by OSA. The research has been done in collaboration with ARCNL colleagues.

Abstract
In this paper, we report on surface-plasmon-resonance enhancement of the time-dependent reflection changes caused by laser-induced acoustic waves. We measure an enhancement of the reflection changes induced by several acoustical modes, such as longitudinal, quasi-normal, and surface acoustic waves, by a factor of 10–20. We show that the reflection changes induced by the longitudinal and quasi-normal modes are enhanced in the wings of the surface plasmon polariton resonance. The surface acoustic wave-induced reflection changes are enhanced on the peak of this resonance. We attribute the enhanced reflection changes to the longitudinal wave and the quasi-normal mode to a shift in the surface plasmon polariton resonance via acoustically induced electron density changes and via grating geometry changes.

Plasmonic enhancement of photoacoustic-induced reflection changes
Guido de Haan, Vanessa Verrina, Aurèle J. L. Adam, Hao Zhang, and Paul C. M. Planken

https://doi.org/10.1364/AO.432659

Schematic depiction of the different types of acoustic excitations presumably observed in our measurements. An ultrafast laser pulse excites the plasmonic grating. The electrons absorb the light and heat up, after which they transfer their energy to the lattice, resulting in high-frequency acoustic waves. From the left to right on the bottom panel we show a schematic depiction of a LW, a SAW, and the grating line quasi-NMs. For the LW and the SAW, the red arrows indicate the direction of propagation of the acoustic waves. For the NM, the red arrows represent the direction of expansion and contraction of the grating lines. Note that the LW will partially reflect to the surface once it reaches the Au/SiOx interface.

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