Side-hole fiber sensor based on surface plasmon resonance.

Surface plasmon resonance (SPR) is demonstrated in a microstructured optical fiber sensor for the first time (to our knowledge). SPR features were observed at 560 and 620 nm when sample fluids of refractive indices n=1.38 and n=1.41, respectively, were applied to the sensor. This study also identifies a new approach to improve the resolution of fiber SPR sensors.

Magnetic-resonance evaluation of the suitability of microstructured polymer optical fibers as sensors for ionic aqueous solutions.

Nuclear magnetic resonance was used to probe the distribution of water and ionic species in a microstructured poly(methyl methacrylate) (PMMA) polymer optical fiber (MPOF), with a plan to assess the suitability of these fibers for aqueous chemosensing. The NMR spectra and the measurements of proton spin relaxation in hydrated fibers demonstrated the presence of two distinct pools of water: water residing in the microstructure channels and the hydration water residing in the polymer matrix of the fiber. No facile chemical exchange between these two pools was present. The NMR peaks of the two pools of water were separated by 1.53 ppm. Relaxation measurements of the fiber samples doped with aqueous copper sulfate showed that charged ions freely entered the microstructure channels but were completely excluded from the polymer matrix of the fiber. Measurements of the apparent diffusion coefficient of water along the axial direction of the fiber showed that water molecules moved unimpeded along the channels. This is the first reported magnetic-resonance study of microstructured optical fibers. The findings suggest that microstructured PMMA fibers are compatible with ionic aqueous solutions and could provide a robust and durable platform for chemical-sensing applications.

Opening up optical fibres.

A unique optical fibre design is presented in this work: a laterally accessible microstructured optical fibre, in which one of the cladding holes is open to the surrounding environment and the waveguide core exposed over long lengths of fibre. Such a fibre offers the opportunity of real-time chemical sensing and biosensing not previously possible with conventional microstructured optical fibres, as well as the ability to functionalize the core of the fibre without interference from the cladding. The fabrication of such a fibre using PMMA is presented, as well as experimental results demonstrating the use of the fibre as a evanescent wave absorption spectroscopy pH sensor using the indicator Bromothymol Blue.

Surface enhanced Raman scattering in a hollow core microstructured optical fiber.

Improvement of surface enhanced resonant Raman scattering (SERRS) signals is demonstrated by confining the scattering event to the core of a hollow core microstructured optical fiber. The analyte solution fills the entire microstructure. The pump light is guided in the liquid core and the Raman scattered signal is efficiently collected by the fiber and transmitted to the detector. Rhodamine 6G (210nM) adsorbed on silver nanoparticles in aqueous solution is used as a demonstration system and it was found that it is possible to collect usable Raman signals from the solution filled optical fiber well beyond the detection limit of an equivalent free-space system.