Light scattering and rheological effects in an optical fibre coupled nanoparticle suspension

Xiang Wang; Rinze Benedictus; Roger M. Groves

doi:10.1117/12.2556799

1 April 2020 Light scattering and rheological effects in an optical fibre coupled nanoparticle suspension

Xiang Wang, Rinze Benedictus, Roger M. Groves

Proceedings Volume 11354, Optical Sensing and Detection VI; 113540V (2020) https://doi.org/10.1117/12.2556799
Event: SPIE Photonics Europe, 2020, Online Only

Abstract

This study forms the first part of research into enhancing the forward and back scattering of light in an optical fibre using nanoparticles (NPs). This approach has the potential to enhance the sensitivity of optical fibre sensing by increasing the signal-to-noise ratio. The work described in this paper is focused on understanding the scattering of light by a suspension of NPs in refractive index matching liquid. It was noted early in the experimental work that rheological effects related to the viscosity and flow of the liquid affect the scattered light measured and therefore these effects are considered in the analysis. Gold nanoparticles in the tens to hundreds of micrometre size range were selected as the scattering particles based on their optical properties. These are suspended in a refractive index liquid with a similar refractive index to the optical fibre core. Effort was needed to transfer the NPs from their aqueous sodium citrate solution to the paraffin based solution. We investigated two types of interaction with the optical fibre: (i) dropping the NP suspension onto the end of a single-mode optical fibre and (ii) using the NP suspension as an interface between two single-mode optical fibres. It was noted that the surface tension of the liquid, the diameter of the fibre and the spacing between the fibres in case (ii) influence the reflected and transmitted light. In case of excess liquid, droplets flowed down the fibre and interestingly in case (ii) modified the reflected and forward transmitted light as it passed across the fibre interface. Our initial findings are that the influence of the gap between two optical fibres decreased after dropping refractive index liquid into the gap after fibre collimation, which is a beneficial result for understanding the influence of scattered light from a liquid containing NPs. Note, the position between the two fibres can also change due to the weight of the droplet and the fibre ends had to be re-collimated to investigate the influence of the moving droplets. These results will be expanded by additional experiments and modelling of the scattering from the nanoparticales and droplets.

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Xiang Wang, Rinze Benedictus, and Roger M. Groves "Light scattering and rheological effects in an optical fibre coupled nanoparticle suspension", Proc. SPIE 11354, Optical Sensing and Detection VI, 113540V (1 April 2020); https://doi.org/10.1117/12.2556799

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