Limits to surface-enhanced Raman scattering near arbitrary-shape scatterers

Mohammed Benzaouia, Jérôme Michon, Rasmus E. Christiansen, Wenjie Yao, Owen D. Miller, Ole Sigmund, Steven G. Johnson*

*Corresponding author for this work

Research output: Chapter in Book/Report/Conference proceedingArticle in proceedingsResearchpeer-review

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Abstract

Various scatterers such as rough surfaces or nanostructures are typically used to enhance the low efficiency of Raman spectroscopy (surface-enhanced Raman scattering). In this work, we find fundamental upper bounds on the Raman enhancement for arbitrary-shaped scatterers, depending only on its material constants and the separation distance from the molecule. According to our metric, silver is optimal in visible wavelengths while aluminum is better in the near-UV region. Our general analytical bound scales as the volume of the scatterer and the inverse sixth power of the distance to the active molecule. For periodic scatterers, a second bound with surface-area scaling is presented. Simple geometries such as spheres and bowties are shown to fall short of the bounds. However, using topology optimization based inverse design, we obtain surprising structures maximizing the Raman enhancement. These optimization results shed light to what extent our bounds are achievable.
Original languageEnglish
Title of host publicationProceedings of SPIE Optics + Photonics 2020
Number of pages5
PublisherSPIE - International Society for Optical Engineering
Publication date2020
Publication statusPublished - 2020
EventSPIE Optics + Photonics 2020 - Online event
Duration: 24 Aug 202029 Aug 2020

Conference

ConferenceSPIE Optics + Photonics 2020
LocationOnline event
Period24/08/202029/08/2020

Keywords

  • Surface enhanced Raman spectroscopy
  • Upper bounds
  • Topology optimization

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