Light scattering by gold nanoparticles cured in optical adhesive at optical fibre interfaces

摘要

This study forms a part of the research in using nanoparticles (NPs) to increase the intensity of light scattering signal in the optical fibres. Increasing the intensity of the backscattered light signal in the optical fibres shows the potential to increase the signal-to-noise ratio in order to improve the sensitivity of the backscatter refiertometry. Doping NPs into the optical fibres can greatly increase the scattered light. However, it is not easy to manufacture NP-doped optical fibres to test different designs. To overcome this problem, in our former work we used the method of dropping refractive index matching liquid containing gold NPs at the optical fibres end tips to investigate the intensity change of the scattered light from the interfaces. In this paper, some new initial experimental results for the scattered light between the optical fibre end tips are shown. Gold NPs have been mixed into the optical adhesive (Norland) and is then dropped and cured at the optical fibre end tips. A backscatter reflectometer (LUNA ODiSI-B) was used in the experiment to measure the intensity of scattered light distribution between the optical fibre end tips. We investigated 4 cases of light scattering between the optical fibre end tips: (ⅰ) the backscattered light intensity distribution in the case of the air gap between the optical fibre end tips; (ⅱ) the backscattered light intensity distribution with optical adhesive between the optical fibre end tips; (ⅲ) the backscattered light intensity distribution with optical adhesive containing gold NPs (gold nanopowder (＜100 nm). Sigma Aldrich) between the optical fibre end tips before curing process and (ⅳ) the backscattered light intensity distribution with optical adhesive containing gold NPs between the optical fibre end tips after the curing process. Our initial findings are that the scattered light by gold NPs at the optical fibre interfaces can be detected by the backscatter refleetometer. By obtaining the differential signal between the distributed light scattering by cured optical adhesive containing gold NPs and only optical adhesive between the optical fibre end tips, the light scattered by the gold NPs has be determined.