The use of designed polymer coatings for specific applications such as drug delivery or modifying cell response is a critical aspect of medical device manufacturing. The chemical composition and physical characteristics of thin polymer coatings need to be analysed in-situ and this can present difficulties for traditional analytical methods. For example, changes in the polarity of polymer coatings are typically measured using the contact angle (CA) method. This is a simple process and gives good results however; it cannot be used to measure very hydrophilic polymers, or to analyse features smaller than a couple of mm in size. There is a need for a non-contact method for polarity measurement that is suitable for hydrophilic polymers on a macro- and microscopic scale. 4'-diethylamino-3-hydroxyflavone (FE), 5, 6-benzo-4'-diethylamino-3-hydroxyflavone (BFE), and 4'-diethylamino-3-hydroxy-7-methoxyflavone (MFE) are fluorescence probes based on 3-hydroxyflavone. They respond to environment perturbations by shift and changes in the relative intensity of two well-separated bands in the emission spectra. These bands originate from an excited state intramolecular proton transfer (ESIPT) reaction. We have incorporated FE, BFE, and MFE into a novel thermoresponsive hydrophilic/hydrophobic copolymer system (NIPAM-NtBA) and studied its fluorescence behaviour. The fluorescence emission spectra depend strongly on copolymer composition, with increasing hydrophobicity (greater NtBA fraction) leading to a decrease in the value of log (IN*/IT*). This allows for the non-contact, measurement of the exact composition and surface energy of the copolymer system.

This paper shows the solublisation and de-bundling of SWNT with an aim to obtaining individual SWNT. By achieving this goal their theoretically proposed properties can be verified and their industrial potential realised. It is well documented that Single Wall Carbon Nanotubes (SWNTs) show varying degrees of solubility in a number of organic solvents. Solubility of SWNTs in toluene was found to be negligible. With toluene having such a poor affinity for SWNT it is clear that the solvent interaction with the SWNT is negligible. Therefore toluene is an ideal candidate for monitoring the improvements in the solubility of the SWNTs as a result of interaction with dye molecules such as terphenyl and anthracene. The suspensions formed are stable for periods greater than thirty-six months. Spectroscopic analysis clearly shows interaction and de-bundling of SWNT on addition of the dye molecules. The fluorescence of the dye molecules is quenched on interaction with SWNTs and in the case of terphenyl, the spectrum is red shifted which gives further support to the notion of interaction. With the quenching in fluorescence of the dye molecules signifying interaction, a large range of concentrations were studied in order to quantify the degree of interaction between the SWNT and dye molecules. It was found at high concentrations such as 1 x 10^-3 M, that both the dye molecules and SWNT formed aggregates. At lower concentrations such as 1 x 10^-9 M for terphenyl and 1 x 10^-6 M for anthracene, it was found that free dye and individual SWNT were interacting. Raman spectroscopy of the composites formed on interaction show vibrational modes that are not present in either the SWNTs or dye powders. It was found that both the dye and SWNTs had Infra Red (IR) active vibrational modes at the positions at which these new or unique Raman modes occur in the composite spectra. It is therefore thought that the new Raman modes in the composite samples are related to the IR modes. The Raman Radial Breathing Modes (RBMs) give detail as to how diameter selective the dye samples are when compared to the pristine SWNT modes. Red shifting of the RBMs for both composite spectra was observed. It is believed that such a result is due to the de-bundling of the SWNT on interaction with the dye molecules.

The application of vibrational spectroscopy to disease diagnosis is a relatively new, rapidly evolving scientific field. Techniques such as Raman and infrared spectroscopy have shown great promise in this regard over the past number of years. This study directly compared Raman spectroscopy and synchrotron infrared (SR-IR) spectroscopy on parallel cervical cancer samples. Both frozen and dewaxed formalin fixed paraffin preserved tissue sections were examined. Both tissue types produced good quality Raman and SR-IR spectra, although the lesser processed, frozen tissue sections displayed the most detailed spectra. Spectroscopy was shown capable of discriminating between different cell types in normal cervical tissue. Spectra recorded from invasive carcinoma showed a marked difference from those recorded from normal cervical epithelial cells. Spectral differences identified with the onset of carcinogenesis include increased nucleic acid contributions and decreased glycogen levels. These investigations pave the way for an enlarged study into this exciting new diagnostic field.

Organic semiconductors molecules are often employed as a thin film interlayer to improve electronic and optoelectronic devices. The characterisation of the interface is thus important to understand the physical properties between the organic thin film and the inorganic semiconductor substrate. Also the orientation of the molecules within the film can be of importance. Two molecules, SnPc and MgPc, are studied on argon sputtered GaAs(001)-1×6 using a surface sensitive synchrotron-based technique, Near Edge X-Ray Absorption Fine Structure (NEXAFS). With NEXAFS, the orientation of the molecule is investigated. It is shown that these two molecules have different orientations in thick films, e.g. SnPc lying close to flat to the surface whereas MgPc is 'standing up'. At the monolayer level, however, the SnPc spectra are unchanged, while the MgPc spectra show an orientation reversal. The spectra are discussed with respect to bulk crystalline strucures.

Determination of photophysical parameters of atoms and molecules is one of the most important problems of fluorimetry. Such parameters are the absorption and excitation cross-sections of a fluorophore, the lifetime of its excited state, the rates of inter- and intramolecular transfer of energy. The tendency to determine as many parameters as possible, especially for multi-fluorophore systems with very high local concentration of the fluorophores, stimulates searching new approaches in fluorimetry. The possibilities of one of such approaches, which can be named "matrix method", are investigated in this paper. In this method, the elements of the matrix of fluorescence intensity values are measured. The arguments of the intensity are not only the wavelength but also the exciting radiation intensity Iexc in the range when the fluorescence saturation manifests itself, the time of the delay T of the registration moment in relation to the exciting pulse etc. The results of numerical modeling of inverse problem of determination of photophysical parameters using the elements of suggested matrix as input data and the neural network algorithms are presented. Results of development of separate sections of matrix method are shown. Experiments were performed with dye solutions and microalgae.

Samples of raw nanotubes are compared to those deposited from solutions to examine separation of nanotube bundles. Single wall nanotubes bundles produced by the arc-discharge and HiPco methods were solubilised in toluene, DMF and 1,2 dichloroethane. Resonant Raman spectroscopy was used to determine if debundling of the tubes sample occurred. The results showed some degree of debundling, best for the 1,2 dichloroethane solvent, which also shows long term solubility.

Photoluminescence intensity PL measurements were taken for a range of PmPV concentrations, in which HiPco single walled carbon nanotubes (SWNTs) at 100%, 10%, 1%, 0.1%, 0.01% and 0% mass fractions were added. The PL intensity of the composite was shown to decrease for all mass fractions, relative to the polymer up to 1.56x10^-3g/l of PmPV, above which there is an initial increase in the composite emission yield with respect to the polymer. This increase is associated with an interaction within the composite, which results in a decrease in polymer aggregate formation, which has been shown to quench intensity yields. Within the concentration range studied 5.9x10^-8g/l to 2g/l the photoluminescence intensity yield for each system is highly non linear. Previously the ratio of the maximum PL intensity of the composite, which includes both, bound and unbound polymer chains, and the maximum PL intensity of the polymer, which includes only unbound polymer chains was plotted as a function of polymer concentration. From this the authors calculated the amount of free polymer within each composite and derived a model, which showed that as the polymer concentration is lowered the bundles break up until isolated SWNTs are stable at low concentrations. In particular for their 100% mass fraction polymer/HiPco SWNT it was shown that individual nanotubes are stable in solutions ~3x10^-5kg/m³. Here we utilize this approach and results indicate that as the mass fraction of nanotubes in reduced, individual nanotubes are stable at higher polymer concentrations. In particular for our 100% mass fraction results indicate that below ~1.5x10^-4g/l individual nanotubes are stable. This result indicates that the choice of polymer and or solvent has a significant effect on the debundling and aggregation within these systems.

Diffusion models predict that polymerization and diffusion rates are the key factors that control the dynamics and the final properties of a holographic grating recorded in a photopolymerizable material. Diffusion rates during the initial phase of the holographic recording have already been studied and reported. We now report the investigation of the polymerization rate in an acrylamide-based photopolymer using Raman spectroscopy. The polymerization rate constant was estimated by monitoring the intensity of the characteristic Raman peaks at 1284 cm^-1 corresponding to the bending mode of CH vinyl bond in acrylamide and 1609 cm^-1 corresponding to the carbon-carbon double bond (C=C) in acrylamide as a function of illumination time. The dependence of the residual monomer concentration on the exposure time was fitted using a mono exponential fitting function. The value of the polymerization constant was estimated to be 0.043 s^-1(mW/cm²)-0.5 for this formulation. A comparison with some other photopolymer systems reported in the literature reveals that the acrylamide-based photopolymer system is characterized by a relatively fast polymerization rate constant. The results from the present study give significant information for better understanding of the process of holographic recording in acrylamide-based photopolymer system.

Research interest in designing sources of cold atoms has significantly increased during the past ten years with the development of suitable laser sources for magneto-optical trapping and the further mastering of evaporative cooling in order to achieve Bose-Einstein condensation. The magneto-optical trap is now viewed as a standard research facility worldwide and has opened up many new exciting research directions in atomic physics. One area of interest is that of combining spherical microcavities with cold atomic sources in order to achieve efficient photon exchange between the cavity and atom for further understandings of cavity quantum electrodynamics. This could eventually lead to atom entanglement via photon exchange which would have implications for quantum logic design. However, initial attempts to achieve such interactions have been hindered by inadequate control and manipulation of the cold atom source. Here, we present work on designing and building an ultra-stable source of magneto-optically cooled rubidium atoms with a temperature in the tens of microKelvin range. We discuss the different cooling mechanisms involved in the process and present a suitable experimental arrangement including details on the ultra-high vacuum chamber, the laser systems being used and the source of rubidium vapour. Finally, we discuss some future direction for the research including the diffraction of atoms from gratings and micron-sized objects and the parameter control of the cloud of atoms.

Micro X-ray Fluorescence (MXRF) has proven to be a powerful tool in the rapid and quantitative means of screening oliogpeptides. MXRF is a non-destructive method of analysis, which can detect elemental composition of a sample by measuring its characteristic X-ray emission wavelengths or energies. An effective high throughput screening technique is described for the rapid screening of bead-based libraries by MXRF in order to identify suitable chelating agents that will bind metals found in radioactive dispersive devices. It is a sensitive technique which in conjunction with the wide range of chemistry inherent in peptide libraries (e.g. varying charge, length, hydrophobicity, aromaticity etc.), provides a rapid and quantitative means for screening chelator-ion binding. The method involves the selection of a suitable library of ligands; in this case it is a bead-based library of peptides. The library is exposed to the cation of interest and immobilized on to a microarray. The array is then analyzed by MXRF enabling rapid identification of chelating agents. This enables the screening of approximately 27,500 sequences per day. Initial experiments carried out successfully identified sequences that are selective for Co under certain binding conditions. This involved the screening of 8,400 sequences in adverse environmental conditions containing possible interferences (e.g. Ca, Fe, Al, Cs, Ir), which could be encountered in our application.

This study into the SPLITS{Sampling Partitioning (Liquid) Irregularities in Turbid Solutions}effect is part of the Aqua- STEW (Water Quality Surveillance Techniques for Early Warning by Tensiographic Sensors) 5th Framework European project. The paper reports new experimental measurements into this effect using the fibre drop analyser. Capillary hydrodynamic fractionation has been previously been observed, but the drop analyser technique provides improved experimental characterisation of the effect. A description of the optical tensiograph system used is given with details of the five strategies designed to minimize this SPLITS effect. It has been observed that the sampling of the solution by a stepper-pump to the instrument drophead, leads to irregular concentrations in the delivery tubing and thence the drophead. The measured tensiotrace variations in successive microlitre samples delivered from the capillary have provided an insightful experimental approach for the study of this important effect. It has been found that the best approach for the minimization of these unwanted concentration irregularities is using high-speed aspiration. The paper ends with discussion on the general relevance of this SPLITS effect to other chemical techniques that must sample turbid solutions and analyses the specific issues posed for on-line water monitoring systems.

Laser-excited Raman microprobe (LRM) spectroscopy has been used for the identification and non-destructive analysis of individual solid phases in mineral-hosted fluid inclusions from Brazilian alkaline rocks. Fluid inclusions from the Pocos de Caldas Massif in Brazil contain remarkable multisolid-bearing fluid inclusions. The size range of the inclusions encountered during microscope examination is between 13 and 70 μm while the solid phases are normally about 10 μm. The LRM revealed the presence of a sodium rich, carbonate-bearing mineral assemblage including the very rare strontium-cerium carbonate Burbankite, usually found in carbonatite or associated rocks.

The majority of soft contact lenses are manufactured using a process of ultraviolet (UV) radiation initiated photopolymerisation. The main source of UV radiation in this manufacturing process is from UV fluorescent lamps. However, there are a number of disadvantages to these lamps, namely, their intensity varies over time and has to be constantly monitored. This paper presents a comparison between light emitting diodes (LEDs), which emit in the UV, and fluorescent lamps used in the contact lens manufacturing industry. The spectral and temporal stability of both UV sources is presented. The ability of both sources to photopolymerise 2-Hydroxyethyl Methacrylate (HEMA), the main component of soft contact lenses, was measured using FTIR and Raman spectroscopy. The percentage polymerisation of HEMA, using both sources, was calculated for several UV sensitive photoinitiators and is presented here. The potential of these UV-LEDs in replacing fluorescent lamps in contact lens manufacturing is discussed.

The unambiguous identification and quantification of hazardous materials is of increasing importance in many sectors such as waste disposal, pharmaceutical manufacturing, and environmental protection. One particular problem in waste disposal and chemical manufacturing is the identification of solvents into chlorinated or non-chlorinated. In this work we have used Raman spectroscopy as the basis for a discrimination and quantification method for chlorinated solvents. Raman spectra of an extensive collection of solvent mixtures (200+) were collected using a JY-Horiba LabRam, infinity with a 488 nm excitation source. The solvent mixtures comprised of several chlorinated solvents: dichloromethane, chloroform, and 1,1,1-trichloroethane, mixed with solvents such as toluene, cyclohexane and/or acetone. The spectra were then analysed using a variety of chemometric techniques (Principal Component Analysis and Principal Component Regression) and machine learning (Neural Networks and Genetic Programming). In each case models were developed to identify the presence of chlorinated solvents in mixtures at levels of ~5%, to identify the type of chlorinated solvent and then to accurately quantify the amount of chlorinated solvent.

In the present investigation, holographic interferometry was utilized for the first time to determine the rate change of the Double layer (D.L) capacitance of aluminium samples during the initial stage of anodization processes in aqueous solution without any physical contact. In fact, because the D.L. capacitance values in this investigation, were obtained by holographic interferometry, electromagnetic method rather than electronic method, the abrupt rate change of the D.L. capacitance was called D.L. capacitance-emission spectroscopy. The anodization process (oxidation) of the aluminium samples was carried out chemically in different sulfuric acid concentrations (0.5-3.125 % H₂SO₄) at room temperature. In the mean time, the real-time holographic interferometry was used to determine the difference of the D.L. capacitance of two subsequent values, dC, as a function of the elapsed time of the experiment for the aluminium samples in 0.5%, 1.0%, 1.5%, and 3.125% H₂SO₄ solutions. The D.L. capacitance-emission spectra of the present investigation represent a detail picture of not only the rate change of the D.L. capacitance throughout the anodization processes, but also, the spectra represent the rate change of the growth of the oxide films on the aluminium samples in different solutions. Consequently, holographic interferometric is found very useful for surface finish industries especially for monitoring the early stage of anodization processes of metals, in which the rate change of D.L. capacitance of the aluminium samples can be determined in situ.

The ideal source of radiation for extreme ultraviolet lithography will produce intense light in a 2% bandwidth centred at 13.5 nm, while the debris and out-of-band radiation produced will be limited to prevent adverse effects to the multilayer optics in the lithography system. In this study ways to optimise plasma sources containing tin are presented. The optimum power density for a tin slab target, with a fixed spotsize, is determined, while the effects of power density on ceramic targets, where tin is present only as a few percent in a target of mainly low Z elements, is also investigated. It has been found that the in-band radiation is increased when the concentration is 5-6%, while the out-of-band radiation is dramatically reduced, due the the low average Z of the target constituents, with conversion effciencies of over 2.5% recorded. The power density needed to optimise the emission from ceramic targets was found to be greater than that required for the pure tin case. In addition, if the target is first irradiated with a pre-pulse, the conversion effciency is seen to increase.

The photoabsorption spectra of Te I-Te IV have been recorded and analysed in the XUV spectral region using the dual laser produced plasma technique. Photoexcitation from the 4d subshell is the dominant process in the 35-150 eV energy region. For photon energies between 35-45 eV discrete structure corresponding to 4d-np (n>4) transitions were obtained. Above the 4d ionisation threshold the spectra of Te I-Te III were found to be dominated by a 4d-ef shape resonance, which peaks at ~88 eV in each case. A transfer of oscillator strength from the resonance to discrete 4d-nf (n>3) transitions with increasing ionisation is clearly evident, and the 4d-4f transitions are the strongest features in the Te IV spectrum. Hartee-Fock with configuration interaction and time dependent local density approximation calculations successfully account for this behaviour and permit identification of the discrete features. The use of a prepulse to maximise the brightness of a tungsten continuum emitting plasma was also investigated.

Hydrocarbon-bearing fluid inclusions (HCFI) are microscopic cavities within rocks that are filled with petroleum oil, the composition of which may not have changed since the trapping event. Thus, the composition of that entrapped oil can provide information about the formation and evolution of the oil reservoir. This type of information is important to the petroleum production and exploration industries. Crude oil fluorescence originates from the presence of cyclic aromatic compounds and the nature of the emission is governed by the chemical composition of the oil. Fluorescence based methods are widely used for analysis of crude oil because they offer robust, non-contact and non-destructive measurement options. The goal of our group is the development of a non-destructive analytical method for HCFI using time-resolved fluorescence methods. In broad terms, crude oil fluorescence behavior is governed by the concentration of quenching species and the distribution of fluorophores. For the intensity averaged fluorescence lifetime, the best correlations have been found between polar or alkane concentrations, but these are not suitable for robust, quantitative analysis. We have recently started to investigate another approach for characterizing oils by looking at Time-resolved Emission Spectra (TRES). TRES are constructed from intensities sampled at discrete times during the fluorescence decay of the sample. In this study, TRES, from a series of 10 crude oils from the Middle East, have been measured at discrete time gates (0.5 ns, 1 ns, 2 ns, 4 ns) over the 450-700 nm wavelength range. The spectral changes in TRES, such as time gate dependent Stokes' shift and spectral broadening, are analyzed in the context of energy transfer rates. In this work, the efficacy of using TRES for fingerprinting individual oils and HCFI is also demonstrated.

A novel prototype instrument for mutli-spectral imaging applications is described. The device is based on an acousto-optic tuneable filter (AOTF) that can be easily attached to many standard imaging systems (e.g. endoscope or fluorescence microscope). The instrument developed offers significant advantages over typical fixed-filter based systems in terms of flexibility, performance and diagnostic potential. The selected AOTF was designed to have a large acceptance aperture suitable for imaging applications. Any filtering centre-wavelength in the visible range (450 to 700nm) can be rapidly selected by either random access or by continuous tuning thus providing a versatile performance. The prototype instrument has been demonstrated for in-vivo applications where it was attached to the eyepiece of a commercial endoscope allowing simultaneous white light and fluorescence endoscopy. Autofluorescence of endogenous protoporphyrin IX (PpIX), a biomarker of diseased tissues undergoing an inflammatory response, was mapped in vivo on a rat model. The AOTF device was also coupled to the viewing port of a commercial fluorescence microscope thus realising a powerful fluorescence imaging spectrometer capable of detecting and mapping fluorescent biomolecules in vitro.

A heterogeneous system composed of zinc oxide nanorods and ruthenium bipyridyl complex dye molecules is described. The photophysical and spectroscopic properties of the system are reported. It has been found that the ruthenium complex binds well to the zinc oxide nanorods and exhibits strong emission properties characteristic of ruthenium complexes. Photoluminescence and emission studies suggest that the ruthenium dye influences the emission and lifetime of the zinc oxide.

We present an overview of incoherent broadband cavity-enhanced absorption spectroscopy (BBCEAS) and discuss its relevance to monitoring atmospherically important gases. Adavantages of the method include its high sensitivity, portability, and good spatial resolution. We present the visible absorption spectra of NO₂ and NO₃ between 600 nm and 720 nm and address issues relating to spectral deconvolution and the simultaneous measurement of multiple gases. The sensitivity of our system is compared to that of other trace gas detection techniques.

The electron photodetachment from 2.5~mM aqueous iodide solution is studied in the temperature range 25 to 75°C. The dynamics following excitation of the anion at 242~nm into the lowest CTTS state are studied in the spectral range of 400-1000~nm. A first intermediate is observed that builds up with a time constant of 220 to 180~fs in the investigated temperature interval and is assigned to an iodine:electron pair in a transient solvent configuration. Subsequent solvent reorganization leads to a quasi-equilibrated hydrated atom:electron pair (I:e^-)_hyd. The latter builds up with a time constant of 700 to 540~fs going from 25°C to 75°C. The following relaxation seems to be governed by partially diffusion-controlled recombination of the electron in the presence of an attraction potential well with depth of about 850~cm^-1. The experimental result for the lifetime of the hydrated I:e^- pair is 21 to 16~ps going from 25°C to 75°C.

Occlusion of a blood vessel due to thrombosis can reduce or completely stop blood supply to different tissues or organs with the clinical consequences of myocardial infarction or stroke. Platelets are the cellular component which initiate thrombus formation, they activate in response to a variety of signals, such as interactions with a damaged blood vessel. α_IIbβ₃ is a membrane bound integrin protein responsible for regulating adhesion of the activated platelet to damaged blood vessels. It exists in both activated and non-activated states displaying high and low affinity respectively for ligands such as fibrinogen. α_IIbβ₃ determines the "stickiness" of the blood platelet and is therefore, a logical target for therapeutic measures to control thrombus formation. During the past decade considerable progress has been made to identify the role of the α_IIbβ₃ complex in platelet-mediated thrombus formation and the structure of α_IIbβ₃ has been extrapolated from the crystal structure of related integrins. However, despite these advances, the bimolecular mechanisms underlying the activation of α_IIbβ₃ remain poorly understood. In this contribution, we describe methodologies of deriving surface enhanced Raman spectroscopy of α_IIbβ₃ on nanostructured metal surfaces, fabricated by a number of methods. We compare activation of α_IIbβ₃ by SERS using a range of known activation conditions including Mn(II), EDTA and dithiotheritol (DTT). By studying the behaviour of the disulfide and CS marker vibrations in the spectral region 400 to 800 cm^-1 using SERS we confirm that activation results in significant conformational change in the protein, and most interestingly, that the response is not the same for every agonist. This mechanistic difference has implications for the biochemical study of this protein (and indeed for understanding the role of this integrin in response to different agonists).

Ultraviolet (UV/Vis) and Electroabsorption (EA) spectroscopy is used to examine and differentiate between intermolecular and intra molecular excited state species in fullerene films. Charge Transfer (CT) states are identified at 2.4 eV and 2.7 eV and dipole moments are calculated. Thermal annealing of C₆₀ films is monitored in situ using absorption spectroscopy and electroabsorption spectroscopy. Recorded spectra display both some temperature dependent and partially irreversible effects, indicating the occurrence of an annealing process. EA shows that the CT states associated with the transferring an electron from the HOMO of one molecule located at the (0,0,0) position to the LUMO of its nearest neighbour in the (1/2,1/2,0) have been modified as a result of the annealing process. Confirmation of this structural change due to the annealing process is provided by previously reported X-Ray crystallographic work.

The synthesis of a series of PPV derivative polymers by the Wittig-Horner reaction is described. The structure of each polymer is varied and the effects of these variations on the optical properties is explored. The effects of alkyloxy side chains is observed between the PPV derivatives Poly(-p-phenylvinylene-co-2,5-bis-octyloxy phenylvinylene.) PPV-OPV and Poly (para-2,5-bis-(n-octyloxy)-phenylvinylene) POPV. The phenyl units of the soluble PPV derivative POPV are replaced by alternate naphthyl units in the polymer Poly(2,5-bis(n-octyloxy)-1,4-phenylene vinylene-1,5-bis(n-octyloxy)-2,6-naphthylene vinylene) POPN-ONV and then fully by naphthyl units in Poly(2,6-bis-(n-octyloxy)-1,5-NaphthyleneVinylene) PONV. The addition of alkyloxy sidechains served to red shift the fluorescence emission as expected. The systematic conversion of phenyl to naphthyl units blue shifted the emission considerably while reducing the Stokes shift. There is evidence to suggest some localization of the pi electrons over the aromatic units of the polymer backbone. PONV is shown to have greater stability towards photo-oxidation then either POPV or PPV-OPV.

A series of π conjugated systems were studied by absorption, photoluminescence and vibrational spectroscopy. As is common for these systems, a linear relationship between the positioning of the absorption and photoluminescence maxima plotted against inverse conjugation length is observed. The relationships are in good agreement with the simple particle in a box method, one of the earliest descriptions of the properties of one-dimensional organic molecules. In addition to the electronic transition energies, it was observed that the Stokes shift also exhibited a well-defined relationship with increasing conjugation length, implying a correlation between the electron-vibrational coupling and chain length. This correlation is further examined using Raman spectroscopy, whereby the integrated Raman scattering is seen to behave superlinearly with chain length. There is a clear indication that the vibrational activity and thus nonradiative decay processes are controllable through molecular structure. The correlations between the Stokes energies and the vibrational structure are also observed in a selection of PPV based polymers and a clear trend of increasing luminescence efficiency with decreasing vibrational activity and Stokes shift is observable. The implications of such structure property relationships in terms of materials design are discussed.

The photabsorption spectrum of I IV-VI, Ba IV-VI and La V-VIII have been recorded using the dual laser produced plasma technique. At lower energies, the barium and lanthanum spectra are dominated by 4d→5p transitions in the regions 76-79 eV and 84-94 eV respectively, whereas for iodine the 4d→nf transitions are dominant between 75-105 eV. For each spectrum, the transitions were identified with the aid of multiconfiguration Hartree-Fock calculations.

The search for a source of EUV radiation for photolithography in the 13.5 nm region has been narrowed down to laser produced or pulsed discharge plasmas containing either xenon or tin. Higher conversion efficiencies can however be obtained with tin based plasmas within this wavelength regime. It is known that EUV photoabsorption by the lower ion stages of xenon reduces the photon flux from a xenon source. This is due to shape resonances from 4d-epsilonf transitions within Xe I-IV. The corresponding resonances for Sn I-IV have been obtained by means of the dual laser plasma (DLP) technique. It is also found that above the 4d ionisation threshold the spectra of Sn I-IV are dominated by a 4d-epsilonf shape resonance which peaks at close to 65 eV in each case. A transfer of oscillator strength from the shape resonance to pseudo-discrete 4d→nf transitions with increasing ionisation is clearly evident. Hartree-Fock with configuration interaction and relativistic time dependent local density approximation calculations successfully account for this behaviour and also permit identification of the discrete features.

In this paper research of behavior of dependencies of characteristics of water Raman scattering valence band on type and concentration of inorganic salts was carried out. It was shown that influence of anions on Raman scattering valence band is much stronger than influence of cations. Explanation of obtained results using theory of ion hydration was suggested. Method of estimation of total hydration numbers, concentration and activity of salts with the help of water Raman scattering band was demonstrated.

The advent of third generation synchrotron light sources has significantly improved our understanding of the quantum chemistry of small molecules. The present study concentrates on processes following the photoexcitation of dissociative resonance states. The investigations were made using two-dimensional, angle resolved time-of-flight photoelectron spectroscopy. Two-dimensional photoelectron spectra show electron yield as a function of photon and electron energy and the comprehensive nature of the data sets often reveals features that are not apparent in one-dimensional photoelectron spectra. The measurements were carried out at the Advanced Light Source on the undulator beamline 10.0.1, which is used for high-resolution atomic, molecular, and optical physics and photoemission studies of highly correlated materials. In the small molecular systems in question, the molecular dissociation time is comparable with the lifetime of the core hole, created by the resonant excitation, so that there is competition between autoionization and dissociation. The two step process of fast dissociation followed by fragment autoionization was first observed for inner shell excitation in HBr and gives rise to sharp peaks in the photoelectron spectrum, at electron energies that correspond to transitions in the excited fragment. Although the sharp peaks may also contain contributions from resonant Auger decay before the fragmentation is complete if the energy separation between the two potential curves becomes constant before the dissociation limit. Alternatively, broader spectral features are associated with electron emission before or during fragmentation, when there is not a constant separation between the potential curves. The existence of indistinguishable channels gives rise to the possibility of observing interference phenomena in the photoelectron spectrum.

This paper is devoted to successful application of artificial neural networks (ANN) for more precise analysis of Raman spectra, and for the solution of the inverse problems of laser Raman spectroscopy. The characteristic peculiarities of the valence band shape of Raman scattering by water molecules in the solutions of KBr, KCl, KI, NaCl, NaI electrolytes have been revealed. These peculiarities allow to perform non-contact recognition of salts type and determination of salt concentration in water solutions by means of artificial neural networks. We suppose that the classification algorithms using the artificial neural networks, applied in this study, may be also useful for other problems in Raman spectroscopy and in fluorimetry, and in application of these methods in ecology.

The problem of determination of oil pollution (OP) in nature water in situ remains topical. Laser fluorimetry as an approach to solution of this problem provides high sensitivity and the opportunity of implementation in remote mode. In this paper, we suggested to use artificial neural networks to extract small contributions of oil pollution to the band of fluorescence of nature water under UV excitation. In this study, we have expanded the set of oil pollution types, which includes different oils.

Use of pulsed lasers opens new opportunities in diagnostics of photosynthetic organisms (PSO). Due to use of pico- and femtosecond laser spectroscopy-absorption spectroscopy and fluorescence spectroscopy-was achieved large progress in study of primary processes of photosynthesis. Orders of magnitudes of many photophysical parameters were determined. In this paper it is proposed for PSO diagnostics one more laser method: method of nonlinear fluorimetry (saturation fluorimetry). This method is based on measuring of nonlinear dependence of fluorescence intensity I_fl on exciting laser radiation intensity I_exc. Because of high local concentration of pigment molecules in PSO chloroplasts dependence I_fl(I_exc) deviates from linear one at sufficiently low values of intensity I_exc≈1 kW/cm². This effect on the one hand complicates the determination of chlorophyll a concentration from the fluorescence intensity; but on the other hand it opens up the possibility of determination of photophysical parameters. The procedure for the determination of the non-saturated fluorescence parameter Φ0 which is proportional to concentration of chlorophyll a molecules and the photophysical parameter A has been elaborated. Parameter A is given by A=στ²γn₀, where σ is the excitation cross-section of chlorophyll a (Chl a) molecules, τ is the lifetime of the excited chlorophyll a molecules taking into account all processes of a deactivation of excitation except the singlet-singlet annihilation, and γn0 is the maximum rate of the singlet-singlet annihilation. In the paper investigations were carried out with aquatic PSO-phytoplankton (PP).

In the paper it is proposed to use fluorescence of dissolved organic matter (DOM) as a water masses indicator. The DOM fluorescence spectra were registered and for two reservoirs of different types: the costal zone of the North Sea and the Rybinskoe reservoir in the middle of the European part of Russia. In the paper it is shown that using normalized intensity of DOM fluorescence and artificial neural networks (ANN) for analysing DOM fluorescence band shape can provide determining the water masses type in natural reservoirs.

We have developed and characterized a new iodine spectrometer for absolute frequency measurements of I₂ transitions at the 633-nm region. This region is important especially in length metrology. To obtain good frequency accuracy, the various sources of frequency shifts in the used saturation spectroscopy configuration have been minimized by optimizing the laser beams for spatial and spectral quality. This is done by injection locking a microlens-coupled diode laser with nearly Gaussian output beam to a stable external-cavity diode laser. The use of the injection-locking scheme also reduces the detrimental effects of optical feedback, as well as residual amplitude modulation related to laser frequency modulation via injection current.

The quantitative analysis of illicit materials using Raman spectroscopy is of widespread interest for law enforcement and healthcare applications. One of the difficulties faced when analysing illicit mixtures is the fact that the narcotic can be mixed with many different cutting agents. This obviously complicates the development of quantitative analytical methods. In this work we demonstrate some preliminary efforts to try and account for the wide variety of potential cutting agents, by discrimination between the target substance and a wide range of excipients. Near-infrared Raman spectroscopy (785 nm excitation) was employed to analyse 217 samples, a number of them consisting of a target analyte (acetaminophen) mixed with excipients of different concentrations by weight. The excipients used were sugars (maltose, glucose, lactose, sorbitol), inorganic materials (talcum powder, sodium bicarbonate, magnesium sulphate), and food products (caffeine, flour). The spectral data collected was subjected to a number of pre-treatment statistical methods including first derivative and normalisation transformations, to make the data more suitable for analysis. Various methods were then used to discriminate the target analytes, these included Principal Component Analysis (PCA), Principal Component Regression (PCR) and Support Vector Machines.

Laser-produced plasma source development for Extreme Ultra Violet (EUV) lithography has concentrated on xenon, since XeXI emits at 13.5 nm, the wavelength at which the reflectivity of MoSi mirrors is centred. However it is not obvious that the required conversion efficiencies can be achieved using xenon, and tin has been identified as a strong emitter at this wavelength. The transitions responsible in tin are 4p⁶ 4dⁿ-4p⁵ 4dⁿ⁺¹ + 4p⁶ 4d^n-14f occurring in a number of adjacent ion stages that merge to form an unresolved transition array (UTA). This UTA is similar to a feature that appears between 10 nm to 11 nm in xenon, which thus provides information directly relevant to tin. The present experimental studies on xenon were performed at the NIST Electron Beam Ion Trap (EBIT). EBITs were developed to perform spectroscopic studies of highly charged ions. The experiments involved changing EBIT parameters, such as the electron beam energy, so that the distribution of ion stages within the plasma changed systematically. Analysis of the corresponding EUV spectra yields information about the contribution of various ion stages to the evolution of the UTA between 10 nm - 11 nm. Previously reported data for the ion stages XeVII through to XeXI are used to identify features occurring in the EBIT spectrum. When the EBIT relative intensities are compared to those from vacuum spark sources they are found to give better agreement with the calculated gA values (statistically weighted Einstein A-coefficients).

X-ray point projection absorption spectroscopy (X-PPAS) is a long established and extremely useful dynamic diagnostic of hydrodynamics, ionization balance, etc. in laser produced plasmas. It has however, to date, been exclusively the preserve of large-scale laser facilities and also used to probe plasmas formed by relatively short pulse (< 1 ns) lasers. We report here the design and selective instrumental performance measures of a new table-top scale X-ray spectrometer system which forms the core of the X-PPAS system. Our design goal is to make X-PPAS a routine diagnostic and also apply it to the measurement of deep inner-shell photoabsorption by plasma atoms and ions.

During the recent years, there has been a growing interest on the physical properties of zirconium dioxide (ZrO₂) for its possible use as high-k material and its application in optical coatings technology as high-refractive index material. In the present work we study the optical and structural properties of ZrO₂ thin films obtained by plasma ion-assisted deposition (PIAD) on silicon wafers, in their as-deposited state and after annealing of the samples at different temperatures. The optical properties were studied by variable angle spectroscopic ellipsometry in the visible spectral range, while the structural properties were analyzed with grazing-incidence x-ray diffraction and x-ray reflectometry. The experimental results show a clear correlation between the optical properties and the variations of the structural properties due to the annealing. Thus, the as-deposited layers show a poor crystalline state, with a low refractive index and energy band-gap. As the annealing temperature was augmented, the degree of crystallinity was increased, as well as the refractive index and the band-gap. Moreover, the annealing also induced a reduction of the layer thickness and a slight increase of the surface roughness.

The importance of sensitive monitoring of changes in Raman spectra in particular for microelectronic applications is discussed here. We explore the practicality of using a data-scattering method to analyse Raman spectra, and to establish the dependence of changes observed in all the spectral function characteristics on the parameters of data-scatter such as scatter closeness and scatter radii using "Trace Miner" software. In addition to the analysis performed on model data, analysis on experimental Raman data is also discussed. The sensitivity of the approach is fully appreciated.

Based on the relationship between spectrum of Einstein coefficient B(v) and optical response _ε2 ^meso for nanostructural materials with different types of size confinement (nanospheres, nanowires and nanowalls) we perform the numerical calculation and analysis of _ε2 ^meso and B(v) functions using dispersive effective field approach for a number of harmonic oscillators with different dispersive parameters (oscillator strength, decay factor and peak frequency). It has been shown that the spectral properties (peak position, peak intensity and half width) of _ε2 ^meso strongly depend upon the type of size confinement. In contrast, the spectrum B(v) is the same for all cases of composite media and therefore has a fundamental meaning. Differences in dielectric functions observed for all studied cases arise as a result of the variation in the local field factor for 3D, 2D and 1D size confinements.

Optical fibre sensor technology has advanced rapidly in recent years, with a feature of current work a strong applications-focus which has become one of the major driving forces for innovation in the field. This paper focuses upon the nature of the background needs and the development of technologies well suited to tackling a range of problems in the assurance of the quality and stability of modern structures, and as a consequence the optimization and the minimization of the costs associated with maintenance of such structures. A number of topical sensor applications are considered and results of recent work presented.

A hand held gas detector is being developed that consists of a laser diode emitting light of wavelength equal to 1651 nm and an extended InGaAs detector. The infrared laser beam is double-passed through a column of air via a folding mirror to a detector. The air column is in contact with the outside atmosphere so that low relative molecular mass hydrocarbon gases, which diffuse into the air column, can be detected by the absorption of some of the infrared light. The absorption at around 1651 nm is due to the overtones of C-H stretching vibrations and the limit of detection of the technique is at the parts per million level. One of the problems of using such a device in the field is that the operator cannot visualise the infrared beam directly. Consequently if the gas detection device fails to give a reading, the operator cannot be sure whether the laser is emitting light and the beam is correctly aligned. The paper describes the use of a novel phosphor screen in order to visualise the beam by converting the infrared radiation into visible light. The properties of a number of phosphors that were developed and tested for the visualisation of the beam will be described. The merits of storage phosphors are compared to those of upconversion phosphors for use at this wavelength, which is longer than wavelengths previously visualised using upconversion phosphors.

A Linear Canonical Transform (LCT) is a general integral transform which can be used to describe a whole host of complex paraxial optical systems. It can be shown that Fourier Transform (FT), Fractional Fourier Transform (FRT), Chirp Multiplication Function (CMT), (which is used as a model for a thin lens), and the Fresnel Transform (FST) are all specific cases of LCT's and are particularly important in optics. Using the Collins ABCD matrix formula it is possible to represent the above integral transforms in matrix notation. Furthermore since most bulk optical systems can be built using lenses of different curvatures (CMT) and free space propagation (FST) it becomes straight forward, to describe optical systems using matrix notation, (which is interchangeable with LCT integral notation). Speckle Photography (SP) can be used in the analysis of surface motion in combination with an optical LCT. It has previously been shown that Optical FRT's (OFRT) can be used in speckle based metrology systems to vary the range and sensitivity of the metrology system. Using a novel correlation technique it is possible to determine both, the magnitude and direction, of tilting (rotation) and translation motion simultaneously. In this paper these ideas are extended to more general LCT's, which allow the consideration of more complicated bulk optical systems. Combined with correlation techniques we experimentally demonstrate our ability to determine both, the magnitude and direction, of tilting (rotation) and translation motion of a surface over a greater range and sensitivity than previous OFRT techniques allowed.

Widely tuneable laser diodes operating in the 1520 ≤ λ ≤ 1570 nm are characterised and compared for use as sources for tuneable laser diode gas absorption spectroscopy. Three gases hydrogen cyanide, ammonia and acetylene with overlapping absorption features within the 50 nm tuning range of the devices were targeted employing wavelength modulation spectroscopy with second harmonic detection.

This paper introduces a new concept in the detection and monitoring of the electric field intensity in high power microwave cavities. It is proposed that the optical emission intensity of a low-pressure gas plasma discharge can be used to describe the strength of the microwave electric field that is powering the plasma. This paper discusses the principles of microwave generated plasmas and demonstrates theoretically using Monte Carlo simulations the emission intensity profile of various gas discharges at varying powers at 2.45GHz and 10GHz. A potential probe design, which uses an optical fibre to couple the discharge emission to a remote photodetector, is also introduced. It is aimed to demonstrate the potential for a new technology that will enable the convenient management of applied microwave power and its spatial distribution.

This paper focuses on optical fiber laser-based wide range temperature measurement applications, under circumstances where different strain values were applied to the chirped fiber Bragg grating at a fixed temperature and the uniform type IIA fiber Bragg grating was used temperature-tuned. This grating forms the end reflector in the laser cavity feedback configuration. Erbium doped fiber was used as the laser gain medium and was pumped by using light from a 1480 nm laser diode. The response of the sensor was achieved over the tunable-temperature range from 70°C to 500°C when a fixed strain value of 1000 με was applied to the chirped Bragg grating, with a root mean square error of 10°C, using linear fitting over the above measurement range.

Distributed Fiber temperature Sensor is a high and new-technology industries that it can be used to measure real-time temperature field distribution of space, WDM (Wavelength Division Multiplexer) is widely used in distributed fiber temperature sensor besides in optical fiber communication system. The characters of WDM especially the isolation and insert loss play an important role in the characters of the sensor. In this paper, the structure of the distributed fiber temperature sensor with WDM applied on was given first. Then the isolation and the insertion loss of WDM are discussed. Analysis and calculation results will be expressed that in this system the characters of WDM determine the accuracy of measurement of temperature.

Chemical and biochemical sensing is under the extensive research all over the world and many chemical and biochemical sensors are finding increasing number of applications in industry, environmental monitoring, medicine, biomedicine and chemical analysis. This is evidenced by each-year-growing number of international scientific conferences, in which advances in the field of the sensors are reported. One of the main reason why only a few sensors reach the international market, notwithstanding the high number of laboratory prototype described in many peer reviewed papers, lies in the fact that a biochemical sensor is a highly interdisciplinary "object" the realization of which requires the team work of scientists coming from different areas such as chemistry, physics, optoelectronics, engineering, biochemistry, and medicine. And this peculiarity is not easily found in the research teams. In the present paper, the fundamental bases of chemical and biochemical optical sensing are summarised and the new trends are described.

We report the development of enhanced optical platforms for fluorescence-based biosensors. A previous analysis by us has shown that the emission of fluorescence in such a system is highly anisotropic and is preferentially emitted into the substrate over a well-defined angular range, with the result that the light is guided along the substrate via total internal reflection. However, conventional optical biosensors based on fluorescence detection typically employ a detector that is positioned either directly above or directly below the biochip. As a consequence, only a small fraction of the total emitted fluorescence is detected, which impacts adversely on sensor performance. The enhanced biosensor presented here is based on a novel, generic platform specifically designed to overcome the inherent limitations of planar substrates. The platform incorporates custom-designed optical elements, the purpose of which is to redirect the emitted fluorescence onto a detector positioned beneath the biochip. Platforms were fabricated using the polymer processing technique of microinjection moulding. In this paper we demonstrate the ability of this optical system to achieve a 80-fold luminescence capture enhancement. We also demonstrate its effectiveness as an enhanced biosensor platform by carrying out a proof of principle BSA/antiBSA competitive assay. This work has significant implications for the development of mass-producible, highly efficient optical biosensors.

The use of information and communications technology in environment management and research has witnessed a renaissance in recent years. From optical sensor technology, expert systems, GIS and communications technologies to computer aided harvesting and yield prediction, these systems are increasable used for applications developing in the management sector of natural resources and biodiversity. This paper presents an environmental decision support system, used to monitor biodiversity and present a risk rating for the invasion of pests into the particular systems being examined. This system will utilise expert mobile technology coupled with artificial intelligence and predictive modelling, and will emphasize the potential for expansion into many areas of intelligent remote sensing and computer aided decision-making for environment management or certification. Monitoring and prediction in natural systems, harnessing the potential of computing and communication technologies is an emerging technology within the area of environmental management. This research will lead to the initiation of a hardware and software multi tier decision support system for environment management allowing an evaluation of areas for biodiversity or areas at risk from invasive species, based upon environmental factors/systems.

Research has shown in recent years that acute and cumulative exposure to excessive ultraviolet radiation (UVR) can cause a range of degenerative ocular conditions such as pterygium, photokeratitis and pinguecula. The increase in natural solar UVR as a result of the depletion of the ozone layer has led to a greater awareness of the adverse effects of UVR on the anterior ocular surface tissues. The relevance of this lies in the fact that these tissues are not immune to photodamage and that there is selective absorption of UVR by conjunctival and corneal tissue in the anterior ocular surface. Therefore, there is a demand for more precise quantification and localisation of UVR incidence at the anterior ocular surface. A novel solar blind photodiode sensor array has been designed, constructed and tested for this purpose. The emphasis of the measurements made by this sensor system is the acquisition of real time, field based surveys of the ocular UVR light field in a broad range of insolation environments. These data will then provide a thorough database of UVR irradiances that can be related to induced damage of anterior ocular tissue. Results to date show the first measured, in-vivo, absolute UVR levels on the eye, the corresponding relative field across the eye and the presence of nasal-temporal biases that exist.

A broad-band green light source for a head-up display is presented. To our knowledge, this is the first report of a green phosphor screen being excited by a blue LED as a backlight for monochrome HUDs. The phosphor screen not only generates the green light but it acts as a diffuser to give a homogeneous illumination. A microlens array focuses the emissions from LED sources on to the diffusing screen eliminating halo effects from the individual LEDs. The purpose of using a green phosphor is to exploit the fact that the eye is sensitive to more shades of green than any other colour. In uses where there are elements of danger such as automobiles (in busy areas), vehicles on construction sites and military vehicles in war zones, green displays have obvious attractions. This paper presents a discussion of the green phosphors that can be used in green screen fabrication, the deposition of the phosphor powders on the screens, the influence of the thickness of the phosphor powder on the screen brightness. In addition, the factors that influence the CIE coordinates of the light emitted from the screen are considered. The importance of choosing the optimum LED emission wavelength along with the general construction of the HUD is discussed. The merits of using a green screen are compared to those when using full colour displays based on white phosphor screens in which yellow emitting phosphors are excited by blue LEDs. Heat management in these HUD devices is achieved by pulsing the LEDs and rastering rows within the LED array.

The development of chromo-reactive sensor spots for real time monitoring of fish freshness is described. The on-package sensor spots incorporating an immobilized pH sensitive dye, respond through visible colour change to basic volatile spoilage compounds collectively known as Total Volatile Basic Nitrogen (TVB-N). Trials on fresh fish filets have verified that the sensor can be employed for real time monitoring of fish spoilage. The sensor response can be interrogated with a simple, inexpensive reflectance colorimeter that we have developed based on two LEDs and a photodetector.

This article is presenting results of label-free detections of biochemical interactions with a simple optical reflectometric concept. While other label-free detection methods need special dimensioned transducers and a high device-related effort, this new principle is working with only one optimal wavelength and is getting qualitatively good results which are absolutely comparable to already established detection methods. We show among other things that it is possible to detect antigene-antibody binding as well as DNA-DNA hybridizations on low cost plastic transducers with this simple 1λ-reflectometry concept.

Widely tunable lasers support certain characteristics which out perform DFB technology for the sensing of gas species in the NIR spectral region. Reduced frequency tuning variation and almost zero residual amplitude modulation (RAM) are investigated. The current report illustrates how 18 individual gas absorption lines can be interrogated using a single laser source over a 40nm wavelength range, where RAM and FM non-linearity never exceed 5% and 13 % respectively. Comparison with DFB technology is made.

The design of a 4 × 1 photon-counting avalanche photodiode array with fully integrated active bias controlling circuit is presented in this paper. The array uses highly sensitive Geiger mode avalanche photodiodes and is capable of detecting four single-photon-level optical signals simultaneously. The photodiode pixels can work either in parallel mode or independently because of the separate gate configuration. The photodiodes are fabricated using a CMOS compatible process with the integrated active quenching and recharging circuit manufactured via 1.5μm CMOS process. The whole system is included on a 2.5mm × 2.5mm die. Simulations show that the fully functional system can detect single photons at up to 20MHz with each pixel or 80MHz with all channels.

An acquisition system pertaining to fiber-optic interferometric sensing is presented. The system consists of a digital signal processor, a codec, laser bias and modulation control circuits, an optical receiver and customized software. The system transmits a modulated light signal to the sensing interferometer, demodulates the returning interferometric signal using the Synthetic-Heterodyne detection technique, while simultaneously relaying control and signal data via PC based software. The system was tested using a low-finesse extrinsic Fabry-Perot cavity, consisting of a cleaved fiber end and a mirror mounted on a piezoelectric cylinder. Applying a sinusoidal voltage to the piezoelectric cylinder vibrated the mirror. Using the interrogation systems, successful retrieval of the vibration signal was obtained for vibrating frequencies from 44 Hz to 4.41 kHz.

In order to meet increasingly stringent emission control laws it is necessary to develop a sensor that can accurately monitor the level of pollutants entering the atmosphere from land transport vehicles. These pollutants are generally a mixture of hot gases and particulates. An optical fibre sensor is particularly well suited to this task. Due to it's small size and weight it is minimally invasive making it suitable for insertion into the vehicle's exhaust system. Optical fibres are immune from poisoning by the analyte gases, although they do require shielding from airborne particulates. As they do not transmit electricity they are also highly safe and furthermore they are immune from electromagnetic interference. To detect the presence of the gases it is proposed to use an optical absorption technique. The majority of gases of industrial and environmental importance have their fundamental absorption line in the mid-infrared region of the electromagnetic spectrum, with weaker overtones in the near infrared. Due to the greater availability of components, optimised for communications, most optical fibre gas sensing has taken place in the near-infrared region of the spectrum. In this paper mid-infrared optical fibre gas sensing techniques are investigated and the results of the investigation are presented. Due to the inhomogeneous state of the gas flow it is necessary to measure temperature especially just upstream of the after-treatment section where this can rise to as high as 650oC with large temporal gradients. Measurements of temperature of hot gases from a full size test engine using an optical fibre probe based on fluorescence decay time measurements are also presented.

A modified opto-electronic method for the determination of velocity, direction of motion and particle size is presented. This method is based on the use of two-dimensional structured photo detector arrays like CMOS-sensors. The principle of measurement utilised is the optical spatial filtering method, which is in widespread use in industrial speed indicators. This technique possesses some interesting advantages such as the use of incoherent light and simplicity of the optical and mechanical set up. In comparison to CCD sensors, new two-dimensional CMOS sensor arrays with direct pixel access allow a faster read out of sub frames. Another advantage of these sensor types is the possibility to realise several spatial filters simultaneously. New more effective measuring procedures can be realised. For instance with two velocity components you are able to describe every plane motion of an object. Thus the determination of direction is made possible. Furthermore, a novel method to determine the particle size by application of a spatial filter can be realised. The possibility of linking pixels inside the sensor (hardware design) makes these spatial filtering methods very interesting particularly with regard to real time systems.

Studies of neurovascular coupling (hemodynamic changes and neuronal activation) in the visual cortex using a time-domain single photon counting system have been undertaken. The system operates in near infrared (NIR) range of spectrum and allows functional brain monitoring to be done non-invasively. The detection system employs a photomultiplier and multi-channel scaler to detect and record emerging photons with sub-microsecond resolution (the effective collection time per curve point is ~ 200 ns). Localisation of the visual evoked potentials in the brain was done using knowledge obtained from electroencephalographic (EEG) studies and previous frequency-domain optical NIR spectroscopic systems. The well-known approach of visual stimulation of the human brain, which consists of an alternating black and white checkerboard pattern used previously for the EEG study of neural responses, is applied here. The checkerboard pattern is synchronized with the multi-channel scaler system and allows the analysis of time variation in back-scattered light, at different stimulation frequencies. Slow hemodynamic changes in the human brain due to Hb-HbO₂ changes in the blood flow were observed, which is evidence of the system's capability to monitor these changes. Monocular visual tests were undertaken and compared with those done with an EEG system. In some subjects a fast optical response on a time scale commensurate with the neural activity associated with the visual cortex was detected. Future work will concentrate on improved experimental protocols and apparatus to confirm the existence of this important physiological signal.

In this work a mechanical optode mounting system for functional brain imaging with light is presented. The particular application here is a non-invasive optical brain computer interface (BCI) working in the near-infrared range. A BCI is a device that allows a user to interact with their environment through thought processes alone. Their most common use is as a communication aid for the severely disabled. We have recently pioneered the use of optical techniques for such BCI systems rather than the usual electrical modality. Our optical BCI detects characteristic changes in the cerebral haemodynamic responses that occur during motor imagery tasks. On detection of features of the optical response, resulting from localised haemodynamic changes, the BCI translates such responses and provides visual feedback to the user. While signal processing has a large part to play in terms of optimising performance we have found that it is the mechanical mounting of the optical sources and detectors (optodes) that has the greatest bearing on the performance of the system and indeed presents many interesting and novel challenges with regard to sensor placement, depth of penetration, signal intensity, artifact reduction and robustness of measurement. Here a solution is presented that accommodates the range of experimental parameters required for the application as well as meeting many of the challenges outlined above. This is the first time that a concerted study on optode mounting systems for optical BCIs has been attempted and it is hoped this paper may stimulate further research in this area.

This work reports synthesis and photochemical studies of 3,6-Bis(3,5-dimethylpyrazol-1-yl)-tetrazine ligand (dmptz) and its Cu(I) complex. Dmptz was found to be an excellent bridging ligand for Cu(I) complexes. The Cu(I) complex has been shown to have a dinuclear structure where a single dmptz ligand links two metal centers. It is apparent that the methyl groups of dmptz have a large steric effect on the structure of the complexes preventing the formation of larger tetra- or penta- nuclear complexes reported in the literature for similar ligands (bptz). We have shown that Cu(I) dmptz complexes possess interesting luminescent properties, that might be potentially used to prepare new luminescent materials for sensing and energy conversion applications.

Re-entrant fiber optic gyro (Re-FOG), using a shorter Sagnac sensitive ring (SSR), makes parts of the two counter-propagandizing lights re-enter the ring before they interference with each other when they reach the photo-detector. Multiple-integrated-optic-chip (MIOC) is one of the most important components of a Re-FOG. In this paper, the principle of the Re-FOG is first reviewed. A method of measuring the half-wave voltage is presented. The thermal induced change of half-wave voltage was tested.

This paper reports on a Fibre Bragg Grating based sensor system, using a LabVIEW interface, for the measurement of strain, primarily in carbon composite materials. The process of embedding the sensors is outlined, system operation is explained and some sensitivity considerations are addressed. The system was firstly used to interrogate a single fibre Bragg grating that was embedded in a cantilever-type sample of a carbon/epoxy laminate. The accuracy of the system was examined by comparing results with those from a conventional resistive foil strain gauge. A composite "smart" panel was then constructed incorporating an array of four FBG sensors. The panel was subjected to various strain conditions, and sensor readings were used to obtain the resultant distribution of strain within the panel. Results were verified using special modelling software.

Temperature sensitive glassware has been developed to monitor liquid chemical temperature in a microwave environment. A combination of two phosphor powders is coated to the base of a Pyrex beaker & Quartz tube, which fluoresce under blue light stimulation. These temperature sensitive glassware monitors changes in liquid or surface temperature by observing ratios of peak emission intensities of the phosphors. The temperature sensitive Pyrex beaker is placed on an oven so that surface temperature can be accurately monitored. A fabricated coated Quartz tube is placed in an Industrial Free Electron Laser (IFEL), which provides the necessary microwave radiation to heat liquids and therefore provide liquid measurements. This paper describes the testing of the coating and its application in monitoring liquid temperature in an Industrial Free Electron Laser.

Due to the development of Fibre Bragg Grating sensors for the measurement of temperature, strain and pressure many markets can benefit from optical technology. These markets are the oil and gas industry, structural and civil engineering, rail and aerospace to name a few. The advantages of using optical sensing technology are that high accuracy measurements can be performed with a passive optical system. By running one fibre along the structure or down the well, multiple points along the fibre can be tested to measure strain, temperature and pressure. Of importance with these systems is the reach that can be obtained while maintaining accuracy. A major problem with long reach system is the back reflection due to SBS and Rayleigh scattering processes which reflect part of the laser light back into the receiver which affect the sensitivity of system. This paper shows a technique to enable a reach of >70km by using a tunable laser and receiver. Techniques for the suppression of receiver noise from SBS and Raleigh scattering are implemented. In addition polarisation dependence of the FBG is considered and results of techniques to limit the effect of polarisation at long and short reaches are shown.

An extensive experimental study into the relationships between tensiotrace features and surface tension of alcohols and bifunctional liquids has produced a series of empirical relationships. The use of this 'inside the rainbow' studies for pendant drops is known as optical tensiography. A series of empirical relationships discovered will enable the experimental measurement of surface tension without the correction factors that have been used since the development of the drop volume/weight method over a century ago for a restricted range of liquids. This approach offers potentially important applications in surface science and it is also suggested how these new relationships will be tested using theoretical models developed by the authors in the ongoing work. This paper provides the first experimental investigation into the commencement of the tensiotrace, a position at which optical coupling begins, which reveals measurement possibilities.

Conventional humanitarian mine detectors based on magnetic and magneto-inductive procedures are able to detect very small metal pieces in the ground. These evaluation methods however result in a high rate of false alarm; the presence of metallic parts detected which are not to be assigned as mines. If you want to classify the metal piece in the ground (e.g. the shape) you have to measure the electro-magnetic field at different positions. Therefore the actual position must be known for each measuring point. By use of the optical spatial filtering method we are able to measure the velocity vector. With the sample time we get the required x-y-position. In our approach we use structured photo detectors as a filter grating and as a detector too. This technique for position determination possesses some interesting advantages such as the use of incoherent light and simplicity of the optical and mechanical set up. New two-dimensional CMOS sensor arrays with direct pixel access allow a fast read out of sub frames. A disadvantage is the slow signal to noise ratio and the price of industrial CMOS cameras that facilitate frame grabbing. The use of simple CCD web cameras limit the maximum measurable velocity, having a read out time of 60 Hz (max), but the price decrease extreme. Early tests using structured photo detectors and spatial filtering methods for position determination show very good results for velocities from 0 to 250 mm/s. A local resolution of 1 mm can be achieved. Tests have also been performed using an ordinary optical mouse as the position determination system.

The development of this photometric device is based on the realisation of a photoplethysmography measurement device developed for the German Space Agency DLR. It is well known in biomedical engineering that pulsatile changes of blood volume in tissue can be observed by measuring the transmission or the reflection of light. The non-invasive multi-spectral method described here is based on the radiation of monochromatic light, emitted by laser diodes in the range of 600 nm to 1400 nm, through an area of skin on the finger. After interaction with the tissue the transmitted light is detected non-invasively by photo-diodes. The method makes use of the intensity fluctuations caused by the pulse wave. The ratio between the peak to peak pulse amplitudes measured at different wavelengths and its dependence on the optical absorbability characteristics of human blood yields information on the blood composition. Deferrals between the proportions of haemoglobin and water in the intravasal volume should be detected photo-electrically by signal-analytic evaluation of the signals. The computed coefficients are used for the measurement and calculation of the arterial oxygenic saturation (SaO₂) and the relative haemoglobin concentration change. Results of clinical measurements are presented for a de-oxygenation study with ICG-bolus injection (indocyanine green).

Current sensor trends, such as multianalyte capability, miniaturisation and patternability are important drivers for materials requirements in optical chemical sensors. In particular, issues such as enhanced sensitivity and printablity are key in developing optimised sensor materials for smart windows for bioprocessing applications. This study focuses on combining novel sol-gel-based hybrid matrices with engineered luminescent complexes to produce stable luminescence-based optical sensors with enhanced sensitivity for a range of analytes including oxygen, pH and carbon dioxide. As well as optimising sensor performance, issues such as surface modification of the plastic substrate and compatibility with different deposition techniques were addressed. Hybrid sol-gel matrices were developed using a range of precursors including tetraethoxysilane (TEOS), methyltriethoxysilane (MTEOS), ethyltriethoxysilane (ETEOS), n-propyltriethoxysilane (PTEOS), phenyltriethoxysilane (PhTEOS), and n-octyltriethoxysilane (C8TEOS). Oxygen sensing, based on luminescence quenching of ruthenium phenanthroline complexes, has been realised with each of these hybrid materials. Furthermore, the possibility of immobilising pH-indicators for pH and carbon dioxide sensing has been investigated with some success. In the context of in-situ monitoring of bioprocesses, issues such as humidity interference as well as the chemical robustness of the multianalyte platform, were addressed.

A technique has been devised for the measurement of surface refractive index of the cornea in human eyes. It has been shown to be effective in laboratory studies of refractive index in optical components of the eye. A modified approach is proposed, in which a much more accurate measurement may be achieved, with the added advantage of reduced patient discomfort. This is achieved by a non-contact method, and frequency-domain analysis of the optical signals used in the characterisation, which are optimised for best signal to noise ratio.

Raman spectroscopy, as an evaluation of the products of ionising radiation exposure in biological systems, has been utilised mainly in the evaluation of the impact of exposure in tissue, cellular constituents and live animals. It has also been recently demonstrated that Raman spectroscopy can demonstrate key spectroscopic changes in the live cell associated with significant apoptotic and necrotic chemical damage. The present preliminary work utilises Raman spectroscopy at 514.5 nm to evaluate the results of exposure to γ-rays in HaCaT cells from a Co-60 therapy source, in tandem with other biological assays. The results demonstrate that Raman spectral changes may be correlated with changes in the cell also identified in parallel biochemical assays.

This paper reports on three methods of classifying the spectral data from an optical fibre based sensor system as used in the food industry. The first method uses a feed-forward back-propagation Artificial Neural Network; the second method involves using Kohonen Self-Organising Maps while the third method is k-Nearest Neighbour analysis. The sensor monitors the food colour online as the food cooks by examining the reflected light from both the surface and the core of the product. The combination of using Principal Component Analysis and Backpropagation Neural Networks has been successfully investigated previously. In this paper, results obtained using all three classifiers are presented and compared. The Principal Components used to train each classifier are evaluated from data that generate a "colourscale" comprising six colour classifications. This scale has been developed to allow several products of similar colour to be tested using a single network that had been trained using the colourscale. The results presented show that both the neural network and the Self-Organising Map approach perform comparably, while the k-NN method tested under-performs the other two.

A dual-laser Raman spectrometer was developed, in which the two lasers image two different parts of the spectrum alternately on the same spectrograph. This solves the resolution/bandwidth trade-off problem of CCD Raman spectrometers, previously solved with a dual-grating technique. The dual-laser technique has, however, an additional advantage of alleviating the contradiction between sample fluorescence and detector response, which is illustrated here by applying the technique to the measurement of paper coating paste.