Felicity Cox

Fabrication and study of microstructured optical fibers with elliptical holes

We report the fabrication of what are believed to be the first microstructured optical fibers with uniformly oriented elliptical holes. A high degree of hole ellipticity is achieved with a simple technique that relies on hole deformation during fiber draw. Both form and stress-optic birefringence are characterized over a broad wavelength range. These measurements are in excellent agreement with numerical modeling and demonstrate a birefringence as high as 1.0 x 10(-4) at a wavelength of 850 nm.

Liquid-filled hollow core microstructured polymer optical fiber

Guidance in a liquid core is possible with microstructured optical fibers, opening up many possibilities for chemical and biochemical fiber-optic sensing. In this work we demonstrate how the bandgaps of a hollow core microstructured polymer optical fiber scale with the refractive index of liquid introduced into the holes of the microstructure. Such a fiber is then filled with an aqueous solution of (-)-fructose, and the resulting optical rotation measured. Hence, we show that hollow core microstructured polymer optical fibers can be used for sensing, whilst also fabricating a chiral optical fiber based on material chirality, which has many applications in its own right.

Selective coating of holes in microstructured optical fiber and its application to in-fiber absorptive polarizers

An interesting feature of microstructured optical fibers (MOFs) is that their properties can be adjusted by filling or coating of the holes. Some applications require selective filling or coating, which has proved experimentally demanding. We demonstrate selective coating of MOFs with metal and use it to fabricate an in-fiber absorptive polarizer.

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.

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.

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.

Solution doping of microstructured polymer optical fibres.

Solution doping of microstructured polymer optical fibres [mPOF] is demonstrated, a technique which allows dopants to be introduced after polymerisation through the microstructure. Controlled diffusion is used to disperse the dopant uniformly across the fibre core, and the final concentration can be systematically varied by appropriate choice of conditions. We use this technique to produce a fibre doped with Rhodamine 6G and characterize its loss and fluorescence behavior.

Microstructured Polymer Optical Fibres: New Opportunities and Challenges

ABSTRACT Microstructured polymer optical fibres [mPOF] were first developed in 2001, and have attracted attention in part because the range of fabrication techniques possible with polymers has allowed novel structures to be made that cannot be made simply in other materials. Their material properties also offer attractive possibilities as polymers can contain a much larger variety of dopants than glass. In this article, we review progress on some of the major challenges of this technology: particularly the need to reduce fibre losses, and report on some recent developments including the fabrication of the first hollow core mPOF. Some initial investigations into changing the material properties are reviewed.

Slotted microstructured optical fibers

A new type of microstructured optical fiber, with a transverse slot running along its length, has been fabricated from polymethylmethacrylate. The slot exposes the fiber core over long lengths, allowing for materials to be directly introduced into the vicinity of the evanescent waves of the core modes. The use of this fiber as an evanescent wave chemical sensor has been demonstrated.

High sensitivity surface enhanced Raman scattering detection in hollow core microstructured optical fibre

Surface enhanced resonant Raman scattering (SERRS) signals are enhanced by confining the scattering to the core of a hollow core microstructured optical fiber. An analyte solution of rhodamine 6G adsorbed on colloidal silver was used. This solution filled both the core and cladding of the fiber. It was found that SERRS signals could be collected from the solution in the fiber beyond the detection limit of an equivalent free space system.