Probing optical resonances of silicon nanostructures using tunable-excitation Raman spectroscopy

M. Matthiae, K.E.S. Nielsen, A. Larroche, C. Zhou, A. Kristensen*, S. Raza*

*Corresponding author for this work

Research output: Contribution to journalJournal articleResearchpeer-review

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Optical materials with a high refractive index enable effective manipulation of light at the nanoscale through strong light confinement. However, the optical near field, which is mainly confined inside such high-index nanostructures, is difficult to probe with existing measurement techniques. Here, we exploit the connection between Raman scattering and the stored electric energy to detect resonance-induced near-field enhancements in silicon nanostructures. We introduce a Raman setup with a wavelength-tunable laser, which allows us to tune the Raman excitation wavelength and thereby identify Fabry-Pérot and Mie type resonances in silicon thin films and nanodisk arrays, respectively. We measure the optical near-field enhancement by comparing the Raman response on and off resonance. Our results show that tunable-excitation Raman spectroscopy can be used as a complimentary far-field technique to reflection measurements for nanoscale characterization and quality control. As proof-of-principle for the latter, we demonstrate that Raman spectroscopy captures fabrication imperfections in the silicon nanodisk arrays, enabling an all-optical quality control of metasurfaces.
Original languageEnglish
JournalOptics Express
Issue number26
Pages (from-to)38479-38492
Publication statusPublished - 2019


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