There is growing demand for biodegradable polymer fibres in tissue engineering and nerve regeneration. We demonstrate a scalable and inexpensive fabrication technique to produce polycaproactone (PCL) fibres using fibredrawing technique. Here we report on the first successful drawing of hollow-core and solid-core PCL fibres of different cross sections. The demonstrated capacity to tailor the surface morphology of PCL fibres, together with their biodegradability and tissue compatibility, makes them a unique material base for tissue engineering and nerve regeneration applications.
We investigate the use of long period gratings inscribed in single-mode microstructured polymer optical fibres for strain
sensing. A simple inscription technique allows gratings to be inscribed with features at visible wavelengths, matching
the transmission window of PMMA. Tracking of the grating features allows strains from 0.05% to over 20% to be
detected, and the inscription of multiple gratings in the same fibre at different wavelengths allows for the possibility of
distributed sensing.
bre Bragg gratings have been inscribed in multimode microstructured polymer optical fibre (POF), with a core size
of 50μm. The microstructured POF (mPOF) consists of a three ring hole structure and is made purely from
poly(methyl methacrylate) (PMMA). In comparison to silica fibre, POF has a much smaller Young's modulus and a
much greater breaking strain; additionally multimode fibre holds advantages of ease of handling and launching
conditions. A linear strain sensitivity of 1.32 ± 0.01pm/με has been measured in the range 0 to 2% strain.
The fibre drawing process leads to a degree of molecular alignment along the fibre axis. This alignment can be
thermally annealed out; this can induce a permanent blue shift in the Bragg wavelength of a grating fabricated prior
to annealing by up to 20 nm. Utilising this, wavelength demultiplexed gratings can be fabricated using a single phase
mask. As an illustration of this we present for the first time wavelength division multiplexing of the spectral
response of three Bragg gratings in POF within the C-band region.
Complementing this work, a technique of splicing mPOF to step index silica fibre is described using UV curing
optical adhesive, allowing characterisation of Bragg gratings fabricated in this fibre.
Long period gratings were written step-by-step in microstructured poly(methyl methacrylate) (PMMA) fibre using a
continuous wave HeCd laser at 325nm irradiating the fibre with a power of 1mW. The grating had a length of 2 cm and a
period of 1mm. A series of cladding mode coupling resonances were observed throughout the spectral region studied of
600 to 1100nm. The resonance wavelengths were shown to be sensitive to both surrounding refractive index and the
water content of the polymer fibre.
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.
Optical fibre sensors have conventionally been made of silica. Polymer optical fibres have a much lower
Young's modulus, and higher elastic limit than silica, and can be incorporated into a large range of
materials. Whilst these properties make them attractive for using in mechanical sensing, using polymers
also brings complexity because of their viscoelastic response. In this work, we use long period gratings
(LPG) in microstructured polymer optical fibre (mPOF) as an optical sensor. The effects of stress and
strain on the sensor are decoupled and analyzed independently. It has been proposed that the relaxation of
stress in the optical fibre during loading would have a significant effect on the interpretation of the optical
sensor output. However through the experiments and modelling in this study it has been shown that the
effect of stress is minimal.
We report on the temperature response of FBGs recorded in pure PMMA and TOPAS holey fibres. The gratings are fabricated for operational use at near IR wavelengths, using a phase mask and a CW He-Cd laser operating at 325nm. The room temperature grating response is non-linear and characterized by quadratic behaviour for temperatures from room temperature to the glass transition temperature, and this permanent change is affected by the thermal history of the gratings. We also report the first FBG inscription in microstructured polymer optical fibres fabricated from TOPAS. This material is fully polymerized and has very low moisture absorption, leading to very good fibre drawing properties. Furthermore, although TOPAS is chemically inert and bio-molecules do not readily bind to its surface, treatment with Antraquinon and subsequent UV activation allows sensing molecules to be deposited in well defined spatial locations. When combined with grating technology this provides considerable potential for label-free bio-sensing.
We report on the temperature response of FBGs recorded in pure PMMA and TOPAS holey fibers. The gratings are
fabricated for operational use at near IR wavelengths, using a phase mask and a cw He-Cd laser operating at 325nm. The
room temperature grating response is non-linear and characterized by quadratic behavior for temperatures from room
temperature to the glass transition temperature, and this permanent change is affected by the thermal history of the
gratings. We also report the first FBG inscription in microstructured polymer optical fibers fabricated from TOPAS. This
material is fully polymerized and has very low moisture absorption, leading to very good fiber drawing properties.
Furthermore, although TOPAS is chemically inert and bio-molecules do not readily bind to its surface, treatment with
Antraquinon and subsequent UV activation allows sensing molecules to be deposited in well defined spatial locations.
When combined with grating technology this provides considerable potential for label-free bio-sensing.
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.
We present measurements on the non-linear temperature response of fibre Bragg gratings recorded in pure and
trans-4-stilbenemethanol-doped polymethyl methacrylate (PMMA) holey fibres.
Photonic crystal fibers technology provides us with new way to obtain fibers with much higher non-linearity than
conventional techniques. Upper limits of non-linear coefficients obtainable in silica-based photonic crystal fibers have
been already investigated. Unique dispersion characteristic and enhanced non-linearity make this kind of fibers an ideal
candidate for non-linear optical devices in telecommunication applications, for measurement and sensing and for
supercontinuum generation. However, there are limitations given by material properties, which obstruct us from
achieving theoretical limits of these fibers. Extremely small core and high air-filling fraction are here needed for reach
higher non-linearity, so when material properties of conventional silica restrict us, there is a requirement on a novel
matter. This could be poly-methyl metacrylate (PMMA), a common material for plastic optical fibers manufacturing.
These microstructured polymer optical fibers are a recent technology, which gives us with new possibilities in core size,
fiber geometry and related air-filling fraction. By this kind of fiber, we could be closer to ideal non-linear fiber, which is
core strain surrounded by air, than even before. But new kind of fiber brings new issues, like which effect in fiber will be
dominant or how will be coupled light affected by outer influences - and what difference will be between predicted and
real values in general. This is a large task and hopefully, there will be answer at least for a small part in this paper.
In this paper we report on investigations of some of the factors that have a bearing on the reliability and repeatability of polymer fibre Bragg gratings. The main issues discussed are the fibre preform composition, the fibre drawing conditions and the thermal history of the fibre grating.
We describe recent research into devices based on fibre Bragg gratings in polymer optical fibre. Firstly, we report on the inscription of gratings in a variety of microstructured polymer optical fibre: single mode, few moded and multimoded, as well as fibre doped with trans-4-stilbenmethanol. Secondly, we describe research into an electrically tuneable filter using a metallic coating on a polymer fibre Bragg grating. Finally we present initial results from attempts to produce more complex grating structures in polymer fibre: a Fabry-Perot cavity and a phase-shifted grating.
The Photonics Crystal Fibers (PCFs) also known as "holey" or "micro-structured" fibers herald a new age for optical fibers. The astronomical applications could revolutionize instrument design through: broadband performance combined with excellent UV transmission, extremely large numerical aperture fibers, and aperture transforming fibers improving input coupling/sampling while maintaining a good match between the fiber outputs and the detector pixels. The Photonic Crystal effects can provide unprecedented non-linear effects in materials and when combined with micro-photonics it is expected that a photonic chip will be realized in which optical switching, wavelength dispersion and even wavelength conversion could take place. However, conventional optical fibers are currently the benchmark for many astronomical applications and improvements in the performance of silica fibers are also being made. In this paper we present a brief review of the current status of photonic crystal fibers with particular focus on the astronomical applications. In addition we present the optical characterization of a new silica/silica broadband fiber that delivers very good transmission from 300nm to 1100nm and beyond.
Microstructured Polymer Optical Fibers (MPOF) were first made in 2001, and subsequent development has aimed at exploiting the material and design opportunities they present. Most effort has been focused on developing approaches for high bandwidth MPOF, and investigating the properties of multimode microstructured fibers. We also consider new applications in endoscopy and photonic interconnects, as well as the use of organic dopants in MPOF.
Microstructured optical fibres (MOFs) have aroused great interest in recent years because of their unusual optical properties. These include their ability to be effectively single moded over a very large range of wavelengths, tailorisable dispersion, high or low non-linearity(depending on the hole design) and large core single mode fibres. We have recently fabricated the first Microstructured Polymer Optical Fibres (MPOFs), which further extend the range of possibilities in MOFs. The properties of polymers can be tailored to specific applications (eg:made highly non-linear or having gain) in a way that is not possible in glass. Further, the large range of fabrication methods available in polymers, including casting and extrusion, mean that the structures that can be obtained are very difficult to make by capillary stacking- the method used in glass MOFs. Here we present the latest results from our group using MPOFs, including single mode fibre and Bragg fibres.
For a large class of practical applications, based on second order nonlinear optical effects, one needs not only noncentrosymmetric molecules, like charge transfer molecules, but also their assemblage to macroscopically noncentrosymmetric materials.
Electric Field Induced Second Harmonic GEneration (EFISH) and the electro-optic Kerr effect were applied to solutions of double stranded DNA, in which the average strand length varied from 2958 base pairs to 140 base pairs. This size range covers the transition from the `rod-like' model (which applies to samples < about 300 base pairs) to the `worm- like' model. In both these electro-optic measurements the electric dipole moment is primarily ionic in nature, and shows a saturating length dependence, although saturation occurred at different lengths. Saturation occurred at longer lengths for EFISH than for the Kerr effect.
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