Femtosecond NUV parallel processing inside PMMA for volume Bragg gratings

Dun Liu - Laser Group, Dept. of Engineering, University of Liverpool

Meeting on Optical Micro & Nano Fabrication Wednesday 3rd November 2010 The International Centre, St Quentin Gate, Telford TF3 4JH

Sub-surface Raman mapping of refractive index microstructures in Polymethylmethacrylate written by femtosecond laser

AncaTaranu - The Photon Science Institute, University of Manchester

Meeting on Optical Micro & Nano Fabrication Wednesday 3rd November 2010 The International Centre, St Quentin Gate, Telford TF3 4JH

Influence of focusing depth and scanning speed on femtosecond laser induced optical microstructures in bulk PMMA

Shijie Liang - The Photon Science Institute, University of Manchester

Palladium coated polymer optical fibre hydrogen sensor for humid environments

Mohammed Akmez Nabeerasool

Sensor Systems for Environmental Monitoring
Thursday, 14th October 2010
At The Royal Society of Chemistry, Burlington House, Piccadilly, London
Organised by the Automation and Analytical Management Group
Royal Society of Chemistry
Email: conference@aamg-rsc.org
Website: http://www.aamg-rsc.org

High-speed uniform parallel 3D refractive index micro-structuring of poly(methyl methacrylate) for volume phase gratings

D. Liu, Z. Kuang, W. Perrie, P. J. Scully, A. Baum, S. P. Edwardson, E. Fearon, G. Dearden and K. G. Watkins (2010). Applied Physics B: Lasers and Optics

Parallel femtosecond refractive index laser inscription of clinical grade poly(methyl methacrylate) (PMMA) at 775 nm, 170 fs pulselength is demonstrated with multiple low fluence beams generated with the aid of a spatial light modulator. Using optimised computer-generated holograms (CGHs), 16 diffracted near identical beams were focused simultaneously within bulk PMMA to create a series of 19 μm pitch, 5 mm×5 mm×1–4 mm thick volume phase gratings at high speed. First order diffraction efficiency rises with grating thickness in accord with diffraction theory, reaching 75% at the first Bragg angle (4 mm thick) with fabrication time around 1 hour. By carefully stitching filamentary modifications while eliminating effects such as pulse front tilt during inscription, gratings exhibit high uniformity, which has not been achieved previously using femtosecond inscription. Highly uniform modification is exhibited throughout the material consistent with the observed excellent angular selectivity and low background scatter and quantitative comparison with first order diffraction theory is satisfactory. The diffraction efficiency and hence refractive index profile shows a temporal behaviour related to the material response after exposure. Simultaneous 3D modification at different depths is also demonstrated, highlighting the potential of creating complex 3D integrated optical circuits at high speed through the application of CGHs.

High repetition rate femtosecond laser processing of metals

Joerg Schille, Robby Ebert, Udo Loeschner, Patricia Scully and Nicholas Goddard. Proc. SPIE, Vol. 7589, 758915 (2010). San Francisco, California, USA, Frontiers in Ultrafast Optics: Biomedical, Scientific, and Industrial Applications X. Sunday 24 January 2010

Previously, in high repetition rate femto second laser processing novel laser matter interacting effects were reported, such as heat accumulation and particle shielding. In this study, high repetition rate laser processing was investigated to discuss and understand the impact of laser repetition rate and accompanied accumulative laser material interacting effects. Therefore, a high repetition rate femto second fibre laser setup joint together with galvo scanner technology was applied in laser micro machining of metals (copper, stainless steel, aluminium). High repetition rate laser processing of aluminium and stainless steel lead to considerably lowered ablation thresholds accompanied with higher ablation rates. Laser ablation behaviour of copper was almost independent of the repetition rate with neither considerable lower ablation thresholds nor higher ablation rates. For explanation, heat accumulation caused by higher repetition rates were assumed as mainly ablation behaviour influencing effect, but thermal material properties have to be considered. Furthermore laser machining examples demonstrate the possibilities and limits of high repetition rate laser processing in 3d micro structuring. Thus, by using innovative scanning systems and machining strategies very short processing times were achieved, which lead to high machining throughputs and attract interest of the innovative laser technology in Rapid Micro Tooling. For discussion, high repetition rate processing results are evaluated by means of comparative machining examples obtained with 1 kHz femto second laser system.

Experimental tensiometric protein adsorption studies

G. Dunne, N.D. McMillan, B. O’Rourke, D. Morrin, M. O’Neill, S. Reidelb, L. McDonell and P. Scully.  Colloids and Surfaces A: Physicochemical and Engineering Aspects, Volume 354, Issues 1-3, 5 February 2010, Pages 364-367.

A novel optical tensiometric method for analysing protein adsorption at liquid interfaces is presented here. The complexities of protein adsorption and desorption processes have been extensively studied and it has been shown that a relatively simple optical tensiometry procedure provides measurements that support those from profile analysis tensiometry (PAT) using sessile drops. Both tensiometry and PAT show the effect of polarity on the adsorption of BSA to different polymers. These processes are also seen during the removal of protein from the polymers.

New tensiographic approach to surface studies of protein kinetics showing possible structural rearrangement of protein layers on polymer substrates

N.D. McMillan, G. Dunne, S.R.P. Smith, B. O’Rourke, D. Morrin, L. McDonnell, M. O’Neill, S. Riedel, J. Krägel, C.I. Mitchell and P. Scully, Colloids and Surfaces A: Physicochemical and Engineering Aspects, Volume 365, Issues 1-3, 5 August 2010, Pages 112-121

An application of optical tensiography is described for studying protein adsorption/desorption/crystallisation processes. This paper concentrates on investigating the physics of the surface kinetics and associated crystallisation processes of the serum protein BSA. The measurements show changes in optical transmission caused by the development of protein layers on surfaces inside a liquid drop. Various absorption mechanisms are evaluated and a physical explanation suggested for the results involving changes in optical scattering as the structure of the protein layers develops. It is shown that tensiography provides a powerful real-time method for monitoring protein adsorption processes on a solid substrate that gives new insights into protein kinetics on these substrates. The study reveals results that are in agreement with earlier work showing multilayer structures and perhaps rearrangement of complex protein layer structures. Finally, consideration is briefly given to potential applications and most importantly the experimental development of this new tensiographic approach for improved real-time absorption measurements of proteins on solid substrates.

Writing Parameters for 3D Refractive Index Structures in Polymethyl Methacrylate Using Femtosecond Radiation at 400 nm

Shijie Liang, Patricia J. Scully, Joerg Schille, John Vaughan, Mohammed Benyezzar, Dun Liu, Walter Perrie. JLMN-Journal of Laser Micro/Nanoengineering Vol. 5, No. 1, 2010

Sub-surface modification by a femtosecond laser, producing pulses of 100fs duration at 400nm wavelength for fabrication of optical components is investigated, within sub-millimetre thick sheets of undoped polymethyl methacrylate (PMMA). For effective structuring, the influence of laser writing parameters and focusing conditions were studied to optimise the pulse energy, pulses spacing and focusing depth in the material. Permanent sub-surface refractive index structures with a minimum feature size (~3μm) at a depth of ~500μm demonstrated the feasibility of writing flexible 3-D microstructures within a thin PMMA substrate. This nvestigation of focusing depth location in PMMA bulk material enabled photonic structures at the desired spatial resolution to be written within the core of single mode polymer optical fibre under controlled laser writing conditions. A long period fibre grating (LPG) consisting of a 2.8μm wide refractive index structure with a periodicity of 250μm and containing a series of attenuation bands in visible range, demonstrated a
photonic structure written into a single mode polymer optical fibre.

Mechanisms of femtosecond laser-induced refractive index modification of poly(methyl methacrylate)

Alexandra Baum, Patricia J. Scully, Walter Perrie, Dun Liu, and Valerio Lucarini, JOSA B, Vol. 27, Issue 1, pp. 107-111, 2010.        doi:10.1364/JOSAB.27.000107 

The mechanisms of refractive index change in poly(methyl methacrylate) by frequency doubled femtosecond laser pulses are investigated. It is demonstrated that positive refractive index modificaton can be caused by a combination of depolymerization and crosslinking.

Plastic Optical Fibre Sensors for Structural Health Monitoring: A Review of Recent Progress

K. S. C. Kuang, S. T. Quek, C. G. Koh, W. J. Cantwell, and P. J. Scully. Journal of SensorsVolume 2009 (2009), Article ID 312053, 13 pages.

While a number of literature reviews have been published in recent times on the applications of optical fibre sensors in smart structures research, these have mainly focused on the use of conventional glass-based fibres. The availability of inexpensive, rugged, and large-core plastic-based optical fibres has resulted in growing interest amongst researchers in their use as low-cost sensors in a variety of areas including chemical sensing, biomedicine, and the measurement of a range of physical parameters. The sensing principles used in plastic optical fibres are often similar to those developed in glass-based fibres, but the advantages associated with plastic fibres render them attractive as an alternative to conventional glass fibres, and their ability to detect and measure physical parameters such as strain, stress, load, temperature, displacement, and pressure makes them suitable for structural health monitoring (SHM) applications. Increasingly their applications as sensors in the field of structural engineering are being studied and reported in literature. This article will provide a concise review of the applications of plastic optical fibre sensors for monitoring the integrity of engineering structures in the context of SHM.

Femtosecond laser induced refractive index structures in polymer optical fibre (POF) for sensing

Liang, S. J.; Scully, P. J.; Schille, J.; Vaughan, J.; Perrie, W., 20th International Conference on Optical Fibre Sensors. Edited by Jones, Julian D. C.. Proceedings of the SPIE, Volume 7503 (2009)., pp. 75036S-75036S-4 (2009).

Techniques to directly write localised refractive index structures in polymer optical fibres (POF) are presented, using UV (400nm) ultrafast laser with pulse lengths of 100 fs to create in-fibre gratings for sensing. No doping is necessary for photosensitisation so commercially available POF is used. An in-fibre grating consisting of a 1.8 μm wide refractive index structure with a periodicity of 189 nm was demonstrated in single mode polymer fibre with optimised laser processing parameters.

Pulse-duration dependency of femtosecond laser refractive index modification in poly(methyl methacrylate)

Alexandra Baum, Patricia J. Scully, Walter Perrie, David Jones, Riju Issac, and Dino A. Jaroszynski. Optics Letters, Vol. 33, Issue 7, pp. 651-653 (2008)

Refractive index modification of pure poly(methyl methacrylate) (PMMA) is investigated as a function of pulse duration using femtosecond lasers at 800 and 387 nm wavelength. It is observed that at 800 nm, the refractive index is modified more efficiently as the pulse duration decreases below 100 fs, whereas at 387 nm, efficient index modification is accomplished with longer, 180 fs pulses. Results suggest that three- and two-photon absorption is responsible for modification of pure PMMA at 800 nm and 387 nm, respectively. Repeated irradiation with short pulses of low laser fluence allows control of the photomodification via incubation, thus reducing bulk damage.

Photochemistry of refractive index structures in poly(methyl methacrylate) by femtosecond laser irradiation

Alexandra Baum, Patricia J. Scully, Maria Basanta, C. L. Paul Thomas, Peter R. Fielden, Nicholas J. Goddard, Walter Perrie, and Paul R. Chalker,  Optics Letters, Vol. 32, Issue 2, pp. 190-192 (2007)        doi:10.1364/OL.32.000190

Femtosecond, subablation threshold photomodification of poly(methyl methacrylate) (PMMA) at 387nm is explored to enable fabrication of optical components. Volatile fragment analysis (thermal desorption gas chromatography-mass spectrometry) and molecular weight distribution monitoring (size exclusion chromatography) suggest photochemical modification, involving direct cleavage of the polymer backbone and propagation via chain unzipping under formation of monomers, similar to the pyrolytic degradation of PMMA. Waveguides were produced in undoped, clinical-grade PMMA, showing an increased refractive index in the laser focal region (Δnmax=4×10−3).

Optical fibre biosensors using enzymatic transducers to monitor glucose

P J Scully, L Betancor, J Bolyo, S Dzyadevych, J M Guisan, R Fernández-Lafuente, N Jaffrezic- Renault, G Kuncová, V Matějec, B O'Kennedy, O Podrazky, K Rose, L Sasek and J S Young, 2007, Meas. Sci. Technol. 18 3177-3186

The construction and performance of a novel enzyme based optical sensor for in situ continuous monitoring of glucose in biotechnological production processes is presented. Sensitive optical coatings are formed from inorganic–organic hybrid polymers (ORMOCER®s*) combined with a flurophore (ruthenium complex) and an enzyme, and applied to lenses, declad polymer optical fibre (POF) and polymer clad silica fibre (PCS). The enzyme, glucose oxidase, catalyzes oxidization of glucose to gluconic acid by depleting oxygen. Oxygen consumption is determined by measuring the fluorescence lifetime of metal organic ruthenium complexes which are quenched by oxygen. The coatings developed were designed to adhere to glass and polymer surfaces, to be compatible with enzymes and ruthenium complexes, and were demonstrated both as double- and single-layer structures. The sensor response to gaseous oxygen, dissolved oxygen and dissolved glucose was measured via fluorescence lifetime changes. A best detection limit of 0.5% (vol) has been determined for gaseous O2 with selected ORMOCER® sensing layers. Glucose concentrations were measured to a detection limit of 0.1 mmol L−1 over a range up to 30 mmol L−1. The sensor was usable for 30 days in a bioreactor. The opto-electronic instrumentation and performance in laboratory bioreactors and in an industrial reactor are evaluated.

Refractive Index Structures in Poly(methyl methacrylate) and Polymer Optical Fibre by Femtosecond Laser Irradiation

A. Baum, W. Perrie, P. J. Scully, M. Basanta, C. L. Thomas, N. J. Goddard, P. R. Fielden, and P. Chalker, " Refractive Index Structures in Poly(methyl methacrylate) and Polymer Optical Fibre by Femtosecond Laser Irradiation," in Optical Fiber Sensors, OSA Technical Digest (CD) (Optical Society of America, 2006), paper TuE25.

Femtosecond laser structuring of un-doped poly(methyl methacrylate) at 387nm produced features < 0.5μm, wave guides and grating structures inside polymer fibre with refractive index change of 3x10-3. Polymer backbone cleavage and monomer formation cause photo-modification.

Polymer optical fibre sensor to monitor skin moisture

John Vaughan, Christopher Woodyatt, and Patricia J. Scully, Proc. SPIE, Vol. 6619, 66191T (2007); doi:10.1117/12.738650, Third European Workshop on Optical Fibre Sensors, Napoli, Italy, Wednesday 04 July 2007

We present a polymer optical fibre sensor to sense skin moisture and droplet formation when sweating occurs. Thesensor used evanescent field attenuation, by exploiting a moisture sensitive cladding with moisture indicator(fluorescein) contained within a porous cladding (HEMA). The sensor was designed to be comfortable to wear andunobtrusive, hygienic, with sterilised interchangeable sensing elements. It had maximum sensitivity between 98% and100% humidity, and response time of 24 seconds.

A novel luminescent lifetime-based optrode for the detection of gaseous and dissolved oxygen utilising a mixed ormosil matrix containing ruthenium (4,7-diphenyl-1,10-phenanthroline)3Cl2 (Ru.dpp)

P. Roche, R. Al-Jowder, R. Narayanaswamy, J. Young and P. Scully, Analytical and Bioanalytical Chemistry,  Volume 386, Number 5 / November, 2006, 1245-1257,  10.1007/s00216-006-0787-5

A novel luminescent lifetime optrode is presented for the detection of gaseous and dissolved oxygen. The optrode utilises ruthenium (4,7-diphenyl-1,10-phenanthroline)3Cl2 as the sensing fluorophore immobilised in a hydrophobic ormosil matrix. The ormosil matrix is synthesised at room temperature from octyltriethoxysilane and methyltriethoxysilane precursors. Investigations of different ormosils were conducted and the most effective one was selected for optrode production. Optrodes were tested for responses to gaseous and dissolved oxygen. Their responses were modelled using traditional two-site or two-exponential methods and feed-forward artificial neural networks. Comparison of the two modelling methodologies is presented and further improvements in modelling and ormosil design are suggested.

Photonic Guided-Path Tomography for Imaging Pressure Distribution Using Polymer Optical Fibre Strain Sensors

S. Joshua, Y. M. Keung, P. J. Scully, and K. Ozanyan, " Photonic Guided-Path Tomography for Imaging Pressure Distribution Using Polymer Optical Fibre Strain Sensors," in Optical Fiber Sensors, OSA Technical Digest (CD) (Optical Society of America, 2006), paper ThE44.

Photonic guided path tomography for imaging of strain on a quasi-planar surface is demonstrated using POF strain sensors. A full set of the forward-transformed data was used for image reconstruction via a ART algorithm.

Optical fibre biosensors for oxygen and glucose monitoring

J. S. Young, Patricia J. Scully, F. Kvasnik, K. Rose, Gabriela Kuncova, O. Podrazky, Vlastimil Matejec, Jan Mrazek. Proc. SPIE, Vol. 5855, 431 (2005); doi:10.1117/12.623688

An optical fibre biosensor that uses an oxygen sensitive coating; Ruthenium complex [Dichlorotris(1,10-phenantroline)-ruthenium(II) hydrate], incorporated into an adhesive inorganic-organic hybrid polymer coating (ORMOCER) is described. The Ruthenium/ ORMOCER layer is used with optical fibres to form an extrinsic or intrinsic sensor. It can be applied to a microscope slide or lens to be interrogated by optical fibres, or form a cladding layer for an evanescent field optical fibre sensor. The Ruthenium complex is caused to fluoresce by a high brightness blue LED at 470 nm and the excitation light at 600nm is detected by a photomultiplier tube used as a photon counter, to measure fluorescence lifetime. The fluorescence is quenched by oxygen depletion within the layer, which can be linked to glucose by incorporation of suitable enzymes. The detection threshold is 0.7mg(O2)/litre, and the sensitivity is 70 ns/mg per litre.

Distributed plastic optical fibre measurement of pH using a photon counting OTDR

C Saunders and P J Scully 2005 J. Phys.: Conf. Ser. 15 61-66  doi: 10.1088/1742-6596/15/1/01

Distributed measurement of pH was demonstrated at a sensitised region 4m from the distal end of a 20m length of plastic optical fibre. The cladding was removed from the fibre over 150mm and the bare core was exposed to an aqueous solution of methyl red at three values of pH, between 2.89 and 9.70. The optical fibre was interrogated at 648nm using a Luciol photon counting optical time domain reflectometer, and demonstrated that the sensing region was attenuated as a function of pH. The attenuation varied from 16.3 dB at pH 2.89 to 8.6 dB at pH 9.70; this range equated to −1.13 ± 0.04 dB/pH. It is thus possible to determine both the position to ± 12mm and pH to an estimated ± 0.5pH at the sensing region.

Femtosecond laser irradiation of polymethylmethacrylate for refractive index gratings

P J Scully, D Jones and D A Jaroszynski, 2003 J. Opt. A: Pure Appl. Opt. 5 S92-S96. 

Polymethylmethacrylate (PMMA) or Perspex is an inexpensive polymer widely used for making the cores of communications grade polymer optical fibres (POFs) and as a substrate for polymer optoelectronic devices and integrated waveguides. Periodic refractive index structures have been written in undoped PMMA using multiple pulses of 40 fs duration from a 1 kHz Ti:sapphire femtosecond laser operating at the fundamental (800 nm). A refractive index change (Δn) of 5 ± 0.5 × 10−4 was observed before the onset of striations. Optimization of writing conditions for refractive index modification of POF fibres or bulk undoped PMMA will enable structures such as Bragg gratings, long-period gratings, mode couplers, microlens arrays, and zone plates to be written.

Femtosecond Laser Modification of Poly(methyl methacrylate) at 387 nm Wavelength

Alexandra Baum, Patricia J. Scully, and Walter Perrie , in Conference on Lasers and Electro-Optics/Quantum Electronics and Laser Science Conference and Photonic Applications Systems Technologies, Technical Digest (CD) (Optical Society of America, 2006), paper JTuD12.

Permanent refractive index modifications (Δnmax= 2×10-3) were induced in clinical grade poly(methyl methacrylate) by UV femtosecond laser irradiation. Holographic writing realised 0.8 µm feature size, enabling gratings in polymer optical fibre and 3-D bulk structuring.

Teaching optics to engineers

Patricia J. Scully and Rebecca J. Bartlett, Proc. SPIE, Vol. 4876, 1379 (2003); doi:10.1117/12.468522, Opto-Ireland 2002: Optics and Photonics Technologies and Applications, Galway, Ireland, Thursday 05 September 2002

The challenges of teaching optics and optoelectronics in a broad basedEngineering school will be discussed. At Liverpool John Moores University, optical devices and optoelectronics is taught from the second year of degree courses right through to MSc level. At second year, students in Broadcast Technology, Applied Electronics have little physics background and are more interested in networks than basic devices and fundamentals of light. Even at MSc level, students' backgrounds are patchy. The challenge is to get across the basic principles in an interesting way, and excite students' interest by focusing on state of the art, current developments and  applications. This is backed up with demonstrations and student projects attached to active research groups. Research groups in the school contribute to teaching in their fields. Members of the Coherent and Electro-optics Research Group teach "Optics and Imaging in Medicine". Members of the Optical Fibre Sensors Research Group teach "Optoelectronics" and "Analogue and Optical Devices". Also discussed are the challenges of teaching Physics students optoelectronics, and the decline of the "Optical Science andTechnology" degree course, due to falling student numbers and thedecline of physics and physics based courses in the UK.

Sensing the fabric: to simulate sensation through sensory evaluation and in response to standard acceptable properties of specific materials when viewed as a digital image

Patricia Dillon, Wendy Moody, Rebecca Bartlett, Patricia Scully, Roger Morgan, Christopher James. Lecture Notes in Computer Science, Springer Berlin / Heidelberg, 0302-9743 (Print) 1611-3349 (Online), Volume 2058/2001, Haptic Human-Computer Interaction, 10.1007/3-540-44589-7, 2001, 978-3-540-42356-0, 10.1007/3-540-44589-7_23, 205-218,

This paper describes initial investigations, primarily from a textile and the related industries perspective, in developing and refining current fabric/texture simulation and interface design. We have considered the interactive possibilities of fabrics within a virtual environment using a simple haptic device, a commercially viable computer peripheral - Logitech’s Wingman Mouse, which was developed by the Immersion Corporation for two dimensional (2D) exploration for the Games industry and desktop web navigation. Also, however because a majority of computer users are accustomed to using a mouse. The Wingman already has the facility to set up some simple mechanical variables to represent some of the more obvious tactile impressions in fabrics, e.g. denim for its overall roughness, and corduroy for its repetitive bumps.
The results and issues involved are discussed in this paper.

Plastic optical fibre sensors and devices

Rebecca J. Bartlett, David F. Merchant, Roger Morgan Transactions of the Institute of Measurement and Control, Vol. 22, No. 5, 431-457 (2000),  DOI: 10.1177/014233120002200507

This paper considers the impact of recent developments in polymer optical fibre (POF) and its application in optical fibre sensors and optical measurement. A discussion of techniques developed for POF-based sensors and devices, and their applications includes sensors to measure flow, biofilm growth, turbidity, toxicity, humidity, rotation and fluorescence. Techniques to photoinduce refractive index changes and physical gratings into POF, and chemically to remove the cladding and taper plastic optical fibres are described, along with the use of fluorescent dye-doped plastic optical fibres (FPOF) in sensors and devices.

Chemical tapering of polymer optical fibre

D. F. Merchant, P. J. Scully and N. F. Schmitt, Sensors and Actuators A: Physical, Volume 76, Issues 1-3, 30 August 1999, Pages 365-371

We introduce a novel method of chemically removing the cladding of PMMA based polymer optical fibre (POF) using organic solvents which can also be used to create etched tapers of any profile within lengths of POF or at fibre ends. The process is simple, inexpensive, low in chemical hazard and operator skill and has application to both improve the performance of numerous POF devices and allow conversion of silica devices to polymer. We give details of the etching processes involved and optical properties of the devices produced. We believe that this is the first application of this chemical process to the tapering of POF cores and suggest possible future applications of the technique.

Optical fibre fluorescence and toxicity sensor

D. Merchant, P. J. Scully, R. Edwards and J. Grabowski, Sensors and Actuators B: Chemical, Volume 48, Issues 1-3, 30 May 1998, Pages 476-484

An optical fibre sensor is presented for the continuous measurement of fluorescent emissions from a fluid sample. The sensor employs a novel patented waveguiding system to allow separation of the excitation and emission wavelengths without optical filtering, has a working range of eight decades with fluorescein and is both chemically and physically robust. The device has applications in process control, flow tracing and environmental monitoring. The authors have developed a novel biochemical toxicity assay technique that produces a fluorescent indication of overall toxicity levels and this assay can be interfaced to the optical fibre sensor to form a rapid online toxicity monitoring device. The assay can be applied to any environment as the test organism is variable. Details of the sensor and aspects of the optical theory are presented together with the results of initial laboratory tests both of the sensor device and the toxicity assay technique.

A new degree course at Liverpool John Moores University: BSc(Hons) Optical Science and Technology

Patricia J Scully and Michael J Wood, Phys. Educ. 32 365-368, 1997.  doi: 10.1088/0031-9120/32/5/022

A new degree course specializing in optics has been established at Liverpool John Moores University. Although built on a core of physics, the course has two distinctive features which make it more than just `Physics with Optics'. Firstly the scope is wide, involving light in its many applications. Secondly, the optics flavour is introduced from the outset. Graduates from the course should be well equipped to work in areas requiring both a knowledge of the physics of light and optical devices and an appreciation of their engineering applications.

Flow sensor using optical fiber strain gauges

Nicolas F. Schmitt, R. Morgan, Patricia J. Scully, Elfed Lewis, and Rekha Chandy,  Proc. SPIE, Vol. 2508, 266 (1995), Conference Date: Monday 19 June 1995, Chemical, Biochemical, and Environmental Fiber Sensors VII, Munich, Germany 

A novel technique for the measurement of air flow velocity using an optical fiber sensor is reported. The sensor measures the deformation of a rubber cantilever beam when subjected to the stresses induced by drag forces in the presence of the airflow. Tests performed in a wind tunnel have indicated a sensitivity of 2 (mu) /(m/s). A qualitative model based on fiber mode propagation has been developed which allows the sensor to be characterized in terms of optical losses. A single 1 mm diameter polymer fiber is mounted on the rectangular section rubber cantilever (section 14 mm by 6 mm) and six grooves are etched into the fiber which extend into the core of the fiber. As the beam deviates the surface deforms (stretches or contracts) and the fiber is subjected to strain. As the strain is increased the grooves become wider and the amount of light transmitted through the fiber is reduced due to increased losses. The sensor described has all the advantages of optical fiber sensors including electrical noise immunity and intrinsic safety for use in hazardous environments. However, its simple construction, robustness, versatility for a number of different fluid applications, as well as relatively low cost make it attractive for use in a wide variety of measurement applications e.g. wind velocity measurement where airborne moisture or chemicals are present.

Optical fiber fluorescence and toxicity sensor

David F. Merchant; Patricia J. Scully; Robert Edwards; Jozef Grabowski, Proceedings Vol. 3105, Chemical, Biochemical and Environmental Fiber Sensors IX,

We present a sensor for the continuous detection of fluorescent emissions from fluids. The sensor utilizes a patented optical fiber detection system to allow separation of the excitation and emission light without the need for optical filters, has a wide working range and has applications in process control, flow tracing and monitoring. The construction, principles and experimental results of the fiber sensor will be given. The authors have also developed a novel test for total toxicity of aquatic systems, the product of which is fluorescent, enabling the proposal of a rapid, continuous and low cost toxicity measurement system. The biochemistry of the test is easily adapted for all types of aquatic environment and expected pollution levels. Results for several heavy metal and organic contaminants, performed under laboratory conditions, are also presented.

Toxicity measurements using fluorogenic compounds

Jozef Grabowski, Peter Baker, Patricia J. Scully,  Proc. SPIE, Vol. 2503, 78 (1995), Air Toxics and Water Monitoring, Wednesday 21 June 1995, Munich, Germany. doi:10.1117/12.221086

Toxicity testing using fluorogenic compounds offers a number of advantages. These include a small sample volume, low cost, rapidity, and applicability to both a micro-organism monoculture and a biocenosis. The method relies on measuring the rate of enzymatic intracellular conversion of a fluorogenic substrate into a fluorochrome. We show how the rate of conversion depends on the substrate concentration, the biomass concentration and pH. We also show how the method can be used to measure the toxicities of several different toxicants, to study antagonistic and synergistic effects of different metal combinations and to study inhibition mechanisms. We then show that it is also possible to measure the cytoplasmic viscosity by exciting the fluorescein molecules in the cytoplasm with polarized light and measuring the polarization of the emitted fluorescence.

Robust and miniature optical fiber pH sensor based on methylene blue dye adsorption

Bruno J. DeBoux, Elfed Lewis, Patricia J. Scully, and Robert Edwards, Monday 10 July 1995, Optomechanical and Precision Instrument Design, San Diego, CA, USA, Proc. SPIE,  Vol. 2542, 167 (1995); doi:10.1117/12.218662

An optical fiber pH sensor based on the surface absorption of methylene blue dye is reported. Previously obtained results for this sensor have indicated a large linear operating range (3-10 pH) coupled with a relatively short response time and immunity to ionic concentration. Further investigations are reported which include testing reproducibility, accuracy, and sensitivity. In addition to this, a two wavelength referencing technique is introduced where the sensor is illuminated by two wavelengths in sequence in a time domain multiplexed manner. The performance of the sensor in terms of temperature stability and immunity to small perturbations to the launch conditions is improved by the application of the multiplexing technique. Particular attention is given to the ability of this sensor to measure pH at very low ionic strength and the geometry of the sensing element has been refined to reduce the response time to below 45 seconds for solutions of ionic strengths of 100 microsecond(s) . These measurements are significant since many applications for pH measurement require operation at such low ionic concentrations, e.g. underground water monitoring. Results are also included for higher ionic concentrations such as those encountered in blood pH measurement and other medical applications.

An Optical Fiber Sensor for Biofilm Measurement Using Intensity Modulation and Image Analysis

POLYMER OPTICAL FIBRE SENSOR TO MONITOR SKIN MOISTURE AND PERSPIRATION

NUV and NIR Femtosecond Laser Modification of PMMA

Riju Issac, and Dino A. Jaroszynski," Pulse-Duration Dependency of Femtosecond Laser Refractive Index Modification In Poly (Methyl Methacrylate),"

Polymer Optical Coatings for Moisture Monitoring

Flow Sensor Using Optical Fiber Strain Gauges (Proceedings Paper)

Optical Fiber Fluorescence and Toxicity Sensor (Proceedings Paper)

Robust and Miniature Optical Fiber PH Sensor Based on Methylene Blue Dye Adsorption (Proceedings Paper)

Wearable Sweat Sensor Using Polymer Optical Fibre

Polymer Optical Fibre Sensor to Monitor Skin Moisture (Proceedings Paper)

Optical Fibre Biosensors for Oxygen and Glucose Monitoring (Proceedings Paper)

High Repetition Rate Femtosecond Laser Processing of Metals (Proceedings Paper)

Photonic Guided Path Tomography

Applications of Haptics-Sensing the Fabric: To Simulate Sensation Through Sensory Evaluation and In Response to Standard Acceptable Properties of …

SENSING AND MEASUREMENT IN HYDROGEN AND FUEL CELLS STATIONARY APPLICATIONS

Optical Sensors and Biosensors for Environmental Monitoring

Toxicity Measurements Using Fluorogenic Compounds (Proceedings Paper)