Nanostructured surface enhanced Raman scattering sensor platform with integrated waveguide core

Pearce, Stuart J., Pollard, Michael, Oo, Swe Zin, Chen, Ruiqi and Charlton, M.D.B. (2014) Nanostructured surface enhanced Raman scattering sensor platform with integrated waveguide core. Applied Physics Letters, 105, 181101. (doi:10.1063/1.4900637).

Abstract

We present a planar waveguide based sensor capable of simultaneous surface enhanced Raman scattering (SERS)/surface plasmon resonance (SPR) sensing methodologies. The sensor consists of a nanostructured area etched into a low loss planar waveguide fabricated from silicon oxynitride. The selective deposition of the 25 nm thick gold film on the nanostructured features was applied to create the SERS/SPR active sites. In this work, we adapt the SPR approach, coupling light propagating along the slab waveguide to the nano-textured area from underneath. The shapes of the nanostructures, thickness, and morphology of the gold coating are chosen to be suitable for SERS and SPR. Effects of geometric parameters associated with the nanostructured features such as diameters, length, and pitch were investigated. Detection of Benzyl Mercaptan was accomplished using a 785 nm laser in a SERS configuration excited from the underlying waveguide core. The detection of the analyte was confirmed by normal incident SERS measurements using an InVia Raman spectrometer. The surface enhanced Raman scattering signal from the 25nm thick Au coated nanostructures provided a maximum intensity signal of 104. Using the same device in the SPR sensing arrangement provided a wavelength shift of 25 nm and an average signal to noise ratio of 10 dB to Benzyl Mercaptan. The fabricated sensor can easily be fabricated using nano imprinting into cheap polymer substrates and would provide disposable real-world remote sensing capabilities.

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