To focus-match or not to focus-match inverse spatially offset Raman spectroscopy: a question of light penetration

Georgina E. Shillito, Lewis McMillan, Graham D. Bruce, Kishan Dholakia

Research output: Contribution to journalArticlepeer-review

2 Citations (Scopus)


The ability to identify the contents of a sealed container, without the need to extract a sample, is desirable in applications ranging from forensics to product quality control. One technique suited to this is inverse spatially offset Raman spectroscopy (ISORS) which illuminates a sample of interest with an annular beam of light and collects Raman scattering from the center of the ring, thereby retrieving the chemical signature of the contents while suppressing signal from the container. Here we explore in detail the relative benefits of a recently developed variant of ISORS, called focus-matched ISORS. In this variant, the Fourier relationship between the annular beam and a tightly focused Bessel beam is exploited to focus the excitation light inside the sample and to match the focal point of excitation and collection optics to increase the signal from the contents without compromising the suppression of the container signal. Using a flexible experimental setup which can realize both traditional and focus-matched ISORS, and Monte-Carlo simulations, we elucidate the relative advantages of the two techniques for a range of optical properties of sample and container.

Original languageEnglish
Pages (from-to)8876-8888
Number of pages13
JournalOptics Express
Issue number6
Publication statusPublished - 2022 Mar 14

Bibliographical note

Funding Information:
Engineering and Physical Sciences Research Council (EP/P030017/1, EP/R004854/1); Horizon 2020 Framework Programme (EC-GA 863203).

Publisher Copyright:
© 2022 OSA - The Optical Society. All rights reserved.

All Science Journal Classification (ASJC) codes

  • Atomic and Molecular Physics, and Optics


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