Publications

Microscopy and spectroscopy

Gold-induced photothermal background in on-chip surface enhanced stimulated Raman spectroscopy

Surface enhanced Raman spectroscopy (SERS) and stimu- lated Raman spectroscopy (SRS) are well established techniques capable of boosting the strength of Raman scattering. The combination of both techniques (surface enhanced stimulated Raman spectroscopy, or SE-SRS) has been reported using plasmonic nanoparticles. In parallel, waveguide enhanced Raman spectroscopy has been devel- oped using nanophotonic and nanoplasmonic waveguides. Here, we explore SE-SRS in nanoplasmonic waveguides. We demonstrate that a combined photothermal and thermo- optic effect in the gold material induces a strong background signal that limits the detection limit for the analyte. The experimental results are in line with theoretical estimates. We propose several methods to reduce or counteract this background.

https://doi.org/10.1364/OL.418527

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Microscopy and spectroscopy

Surface-enhanced Raman spectroscopy based on plasmonic slot waveguides with free-space oblique illumination

In our quest to demonstrate an all-on-a-chip Raman spectrometer, we are reporting a configuration that strongly suppresses background noise typical of the SiN photonics waveguides. We use an excitation of a plasmonic waveguide that is oblique so that the molecules within the plasmic waveguides are Raman excited but the pump light is not properly coupled to the waveguide but only slightly scattered. As only scattered light is coupled to the collecting SiN waveguide, the pump-induced background photon noise is highly suppressed. Moreover, the plasmonic structure and the incidence angles are engineered so that there is a resonant enhancement thus boosting further the field of the pump beam.

REFERENCE: Y. Li, H. Zhao, A. Raza, S. Clemmen, R. Baets, Surface-enhanced Raman spectroscopy based on plasmonic slot waveguides with free-space oblique illumination, Journal of Quantum Electronics, 56(1), p.paper 7200108 (2020) DOI

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Microscopy and spectroscopy

Plasma-enhanced atomic layer deposition of nanostructured gold near room temperature

A new method for depositing gold via atomic layer deposition creates nanostructures that boost the plasmonic response of gold. We take advantage of this extra enhancement for the Raman spectroscopy of biological monolayers.

REFERENCE: M. Van Daele, M. Griffiths, A. Raza, S. Matthias, F. Eduardo, J.-Y. Feng, R. Ramachandran, S. Clemmen, R. Baets, S. Barry, C. Detavernier , J. Dendooven, Plasma-enhanced atomic layer deposition of nanostructured gold near room temperature, ACS Appl. Mater. Interfaces, 40(11), p.37229-37238. (2019) DOI

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Microscopy and spectroscopy

High index contrast photonic platforms for on-chip Raman spectroscopy

We compare several high-index-contrast photonics platforms in term of their suitability for on-chip Raman spectroscopy.

REFERENCE: A. Raza, S. Clemmen, P.C. Wuytens, Michiel de Goede, Amy Tong, N. Le Thomas, Chengyu Liu, Jin Suntivich, Andre Skirtach, Sonia Garcia-Blanco, Daniel Blumenthal, James Wilkinson, R. Baets, High index contrast photonic platforms for on-chip Raman spectroscopy, Optics Express, 27(16), p.23067-23079 (2019) DOI

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Microscopy and spectroscopy

SERS detection via individual bow-tie nanoantenna integrated in SiN waveguides

Embedding plasmonic antenna within SiN waveguides improves the coupling of Raman scattered light to the mode of a SiN waveguide.

REFERENCE: J. Losada, A. Raza, S. Clemmen, A. Serrano, A. Griol, R. Baets, A. Martinez, SERS detection via individual bow-tie nanoantenna integrated in SiN waveguides, IEEE Journal on Selected Topics in Quantum Electronics (2009)  DOI (2019).

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