Advantage of multi-mode sapphire optical fiber for evanescent-field SERS sensing

An unclad, multi-mode single crystal sapphire fiber was used as a platform, and immobilized colloidal Ag nanoparticles (NPs) were used as enabler, for evanescent-field fiber-optic sensing via surface-enhanced Raman scattering (SERS) of Rhodamine 6G (R6G) solution. The dependence of the measured Rama...

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Bibliographic Details
Published in:Optics letters 2014-10, Vol.39 (20), p.5822-5825
Main Authors: Chen, Hui, Tian, Fei, Chi, Jingmao, Kanka, Jiri, Du, Henry
Format: Article
Language:English
Subjects:
Aluminum Oxide
Density
Detection
Dominance
Fibers
Metal Nanoparticles - chemistry
Nanoparticles
Optical Fibers
Raman scattering
Rhodamines - chemistry
Sapphire
Silver - chemistry
Spectrum Analysis, Raman - instrumentation
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Summary:An unclad, multi-mode single crystal sapphire fiber was used as a platform, and immobilized colloidal Ag nanoparticles (NPs) were used as enabler, for evanescent-field fiber-optic sensing via surface-enhanced Raman scattering (SERS) of Rhodamine 6G (R6G) solution. The dependence of the measured Raman intensity on NP coverage density (to a maximum of 120  particles/μm²) as well as the coverage length (to a maximum of 6 cm) was investigated. We demonstrate the utility of SERS-active sapphire fibers for sensitive measurements (10⁻⁸ M R6G). We further reveal, with the aid of theoretical analysis, that multi-mode fiber offers a significant advantage compared to its single-mode counterpart because the former allows two orders of magnitude higher particle coverage density than the latter to maximize SERS benefit, while maintaining the dominance of Raman gain despite the competitive interplay of NP-induced absorption and scattering loss along the interaction path length.
ISSN:0146-9592
1539-4794
DOI:10.1364/OL.39.005822