A fiber optic hydrogen cyanide (HCN) sensor having its entire length as the sensing element is reported here. The optical fiber is multimode and consists of a pure fused-silica core and an HCN sensitive cladding. Upon exposure to HCN gas, the cladding rapidly changes color, resulting in attenuation of the fiber's light throughput. The fiber is used to detect HCN at part per million levels, which suggests that the propagating modes of light interact with the cladding. The sensitivity of the fiber as a function of sensor length and challenge concentration will be reported. Prior to exposure, the fiber attenuation measures less than 1 dB/m, making it possible to detect hydrogen cyanide on a continuous length of fiber on the scale of tens of meters. This technology could replace the need for having a collection of point-detectors to cover large areas, and hence lends itself to building and perimeter chemical detection.

A distributed feedback (DFB) laser diode emitting at 785 nm was used as light source for Raman spectroscopy. An in situ surface enhanced Raman spectroscopic (SERS) sensor was developed to detect polycyclic aromatic hydrocarbons (PAHs) in marine environment at concentration levels down to nmol/l. The DFB diode used in our SERS experiments had an output power of 150 mW at 785 nm and a spectral linewidth of 3 MHz. The wavelength stability of this laser was ± 0.004 nm over 12 hours. A side mode suppression ratio up to 45 dB was determined. For trace detection of chemicals in marine environment, SERS active substrates were employed based on silver colloids encapsulated in a sol-gel derived matrix. The resulting spectra and a limit of detection (LOD) of phenathrene (34 nmol/l) as an example for PAHs in seawater are presented. A concentration of 1 nmol/l of pyrene was detected.

Protecting the nation's drinking water from terrorism, requires microg/L detection of chemical agents and their hydrolysis products in less than 10 minutes. In an effort to aid military personnel and the public at large, we have been investigating the ability of surface-enhanced Raman spectroscopy (SERS) to detect microgram per liter (part-per-billion) concentrations of chemical agents in water. It is equally important to detect and distinguish the hydrolysis products of these agents to eliminate false-positive responses and evaluate the extent of an attack. Previously, we reported the SER spectra of GA, GB, VX and most of their hydrolysis products. Here we extend these studies to include the chemical agent sulfur-mustard, also known as HD, and its principle hydrolysis product thiodiglycol. We also report initial continuous measurements of thiodiglycol flowing through a SERS-active capillary.

This paper describes the development of a compact, self-contained, and portable Raman Integrated Tunable Sensor (RAMiTS) for chemical and biosensing. The RAMiTS consists of a frequency-stabilized diode laser for excitation, an acousto-optic tunable filter (AOTF) for wavelength discrimination, and an avalanche photodiode (APD) for detection. It can provide direct identification and quantitative analysis of chemical and biological samples in a few seconds under field conditions. Instrument control and data acquisition was coordinated by software developed in house using the C language. Evaluation of this instrument was performed by analyzing several model compounds and the high spectral resolution of this instrument was demonstrated by the discrimination of several structurally similar molecules (benzene, toluene and naphthalene) as well as m-, o-, p- isomers of xylene. The potential applications of the RAMiTS coupled with the surface-enhanced Raman scattering (SERS) for the detection of chemical and biological warfare agents will also be discussed in this paper.

The ability to engineer polymer materials that have special response to external factors as well as to incorporate nano- and/or micro- materials in these polymer matrices make these materials perfect candidates for physicochemical sensors. The incorporation of the nano-/micro-materials help the polymer materials become more sensitive to a variety of external factors. Different polymer designs for the detection of humidity, alcohols and hydrocarbons are described. Special diffractive photonics structures are implemented to offer increased sensitivity to physicochemical changes. The final photonic sensor design is based on an optimization of chemical as well as optical design. The chemical polymer designs are based on selecting and synthesizing the appropriate polymeric structure that will facilitate interaction with the analyte, through a number of physical and chemical processes (adsorption, solubilization, entrapment, coulombic interaction and hydrogen bonding). These functions are determined by the chemical and structural features of the polymer used i.e. functional groups, glass transition, porosity, etc. In the case of polymer/nano- and/or micro-inorganic hybrid materials, interactions of the polymer matrix with the inorganic component(s) and dispersion of the nanomaterials within the matrix have to be taken into account. Suitable photonic interfaces based on transmissive and/or diffractive techniques are designed to provide the medium with interface tailoring and interrogation methodologies. Novel photonic information processor prototype devices based on free space configurations are demonstrated to extract/recover the captured information from the sensing material. The advantageous characteristics of the presented integrated sensor are the fully reversible behavior, at ambient operating conditions, without the need for additional heating or light exposure.

The continuous monitoring of interstitial pH, pO₂ and pCO₂ contained in the adipose tissue of intensive care patients, is one of the objective of the four year European project CLINICIP (Closed Loop Insulin Infusion in Critically Ill Patients). A glass capillary on line with the microfluidic system, is the solid support onto which the appropriate chemistry is immobilised. The optical working principle applied for the detection of oxygen and carbon dioxide is the modulation of the fluorescence lifetime, whereas absorption modulation is the approach followed for the pH detection. On this basis, two different optoelectronic units were developed for the interrogation of the glass capillary, one for life-time measurements and the other for absorption measurements. Preliminary tests demonstrated a resolution of 0.03 pH units for pH; ≤ 0.55 mmHg for oxygen and ≤ 0.6 mmHg for carbon dioxide; and an accuracy of 0.07 pH units for pH; ≤ 1 mmHg for oxygen and ≤ 1.5 mmHg for carbon dioxide.

In this article we present a very simple, transducer-independent label-free optical detection method based on reflectometry for bioanalytical applications. A laboratory setup of this 1λ-reflectometry delivers results that are comparable with established detection principles like Surface Plasmon Resonance or Reflectometric Interference Spectroscopy. Additionally we present a first version of a miniaturized setup of this method to show its potential due to its simplicity.

An optical fiber sensor is being developed for diagnosis of human breast cancer cell lines. The sensor exploits laser-induced fluorescence spectroscopy in conjugation with fiber optics. The main advantage of fluorescence detection compared to absorption measurements is the greater achievable sensitivity due to the fact that the fluorescence signal has a very low background. However, an accurate and sensitive method for the diagnosis of cancer cell lines is quit challenging. The sensitivity and accuracy of LIF technique can be improved by optimizing the sensor configuration. In this work, the spectral characteristics of the fluorescence, which was induced by frequency tripled Nd:YAG laser operating at 355nm are recorded from two different type of human breast cancer cell line. Effects of various influential experimental parameters and configuration were investigated in order to optimize the sensor performance. The sensor with optimum configuration enables to differentiate two types of cancerous cell lines with a maximum achievable fluorescence spectral contrast. A unique data processing technique has been developed to analyze the recorded data for cell lines identification and differentiation.

The growth in utilization of sensor networks in every field of science has compelled the research community to device a common addressing technique for sensor networks. To achieve this, we propose an addressing and naming scheme for sensors based on a hierarchical model of the sensor network in this paper. We show that, the complete scheme allows accessing and tracking sensor devices by names and inherently facilitates data aggregation. We study the performance of and optimize the hierarchical architecture and use algorithms for bounding timing delays, width and height. Finally, we suggest a gateway-based architecture to establish a secure layer above the routing protocol to perform safe communication and location tracking. From our analysis it is seen that the methodology can be adopted for various scenarios like disaster areas, habitat monitoring, target tracking, medical monitoring, battlefield, etc.

Simulations and experimental results for novel refractometric-sensing platforms are presented here. The first platform is based on a multi-mode interference coupler (MMIC) in which the top and sidewalls of the coupler are exposed to a humidity-sensing enrichment layer. Sensor operation is based on the creation of self-images of the input field into the coupler, at regular intervals along the coupler. This phenomenon is due to interference between the optical modes in MMICs. Changes in the refractive index of the sensing layer cause predictable shifts in the position of the output image, which in turn affects the amount of light coupled into the output waveguide. Sensitivity enhancement has been demonstrated by fabricating longer MMICs capturing higher-ranking self-images, which are shifted more than the first self-image. Consequently, more significant changes in the amount of light coupled to the output are observed for a given refractive index change. The second platform demonstrated is a Multi-Channel Directional Coupler sensor (MCDC). It differs from the MMIC in that the sensing region now consists of multiple single-mode waveguides, which are in close enough proximity to allow light to transfer between the waveguides. Sensitivity dependance on platform length has been investigated and compared with that of the MMIC. The devices have been fabricated by the direct laser writing process on UV curable hybrid sol-gel materials. Such materials allow implementation of planar technology enabling integration on a silicon substrate. Future applications of these platforms include chemical and bio-chemical sensing is the areas of process, environmental and bio-diagnostic monitoring.

Since biological materials possess some degree of chirality a full wave solution for the scattering of electromagnetic waves (including optical and infra-red wavelengths) at an irregular interface between free space and a chiral medium is derived. To this and the electromagnetic fields are expressed in terms of Generalized Fourier Transforms. These transforms provide the basis for converting Maxwells equations, together with the associated exact boundary conditions, into Gneralized Telegraphists' Equations for irregular stratified media. Scattered near fields as well as far fields can be obtained from the solutions for the Generalized Telegraphists equations. The Mueller elements are related to the linear like and cross polarized far field scattering matrix. All sixteen Mueller Matrix elements of Bio-Medical Materials are examined. Special attention is given to the eight quasi off diagonal elements of the Mueller Matrix in order to examine the feasibility for detection and identification of bio-medical materials. The specific impact of chirality on the Mueller Matrix elements is analyzed. It is shown that (to within first order of the chirality parameter) only the eight quasi off diagonal elements of the Mueller Matrix are effected by the chiral property of the bio-medical materials. This reinforces the experimental observation from previous scattering experiments that the quasi off diagonal Mueller Matrix elements could provide a basis for bio-medical detection and identification. The analysis provides the explicit relationship between the quasi off diagonal elements and the degree of chirality of the bio-medical materials.

A focus on soil quality issues in the EU has resulted in extensive studies aimed to development of a Soil Framework Directive, in parallel with setting up a harmonized European Soil Monitoring System. Polycyclic Aromatic Hydrocarbons (PAHs) belong to the most problematic contaminants to be monitored and controlled. This study presents the screening survey for 16 PAHs carried out in 2000 in the area severely impacted by the catastrophic flood of 1997 in the Odra River valley in Poland, Czech Republic and Germany. Within this survey, 16 PAH contents in soils due to river sediments deposition resulting from the flood, and the effect of flood on the distribution of PAHs in soils of the area were assessed in view of soil quality standards and need for remediation. The post-flood PAH spatial distribution with use of the Geographical Information System (GIS) showed distinct correlation with floodwater flow conditions, while total 16 PAH and specific compounds concentrations in the soil layer 0-0.20 m appeared to be mostly within the standard limits. In 17% of composite samples, 16PAH concentrations were found to be considerably elevated, up to the values > 1000 μg/kg exceeding the standards for agricultural soils in particular samples. PAH compounds displayed also different vertical migration potential in soils. The occurrence of the maximum PAH concentrations in the floodwater stagnation areas confirmed river sediments to be the major source of these compounds. The qualitative composition of 16 PAHs (ANty < Flth < CHR < BaA < PYR) in humus layer of soils in these areas denoted anthropogenic sources of these compounds.

The chemical state of groundwater in the Major Groundwater Basin (MGWB) 332 was assessed on the grounds of hydrogeochemical monitoring conducted in 2001-2003 in the network that comprised 37 monitoring wells (points). On the basis of concentration data of organic and inorganic chemical constituents, the chemical quality of water in the monitoring wells was evaluated. Aggregated data were used for an assessment of the chemical state of the whole basin. The evaluation of the water quality in the monitoring wells was conducted in accordance with the Directive of the Minister of Environment (RMS, 2004) by the comparison of concentrations of analyzed chemical constituents with limit values in the quality classes I-V. In general, the water quality fulfilled the criteria of III class, occasionally of IV and V.class. Water chemical state in MGWB 332 was evaluated as good, following the criteria specified in the EU Water Framework Directive 2000/60/EC and the draft EU Directive on the protection of groundwater against pollution (COM 2003), based on the mean values of chemical indicators for the whole basin. The recommended method of the chemical state assessment on the basis of mean concentrations in all the monitoring points caused vanishing the zones of unsatisfactory quality (class IV) in the averaged backgrounds. In practice, this will result in desisting from any action aiming to improvement of water quality in these zones. The results of this study show the need of reporting chemical state of groundwater quality also in the specific monitoring points, and not just in the averaged hydrogeologic units or subunits.

Surface enhanced Raman spectroscopy (SERS) has enormous capabilities for the unambiguous identification of artists' red lake pigments and dyestuff. Until now, red lake pigments have been very poorly characterized with conventional Raman spectroscopy due to their high fluorescence and weak Raman scattering cross section. Furthermore, very small amount of dyestuff is necessary to achieve intense deep colors; therefore a characterization method with enhanced sensitivity is needed to accurately identify the dyestuff. This study focuses on two red dyestuffs, carminic acid and laccaic acid, which are extensively utilized in old masters' paintings. We propose an innovative sensing method using 6 nm silver island films (AgIFs) fabricated with electron beam (e-beam) deposition on the colorant particles under investigation. The results of an in-depth methodological investigation into the signal-enhancement achievable with various experimental conditions applied to these substrates are presented. We explore the effects of varying laser excitation frequencies (532.15 nm 632.8nm and 785.7 nm), laser power at the sample and we investigate the dependence of S/N in the spectra from different spot sizes. Finally, the sensitivity of the method is determined. The results of the semi-quantitative analysis have allowed us to determine the best experimental conditions to achieve the highest sensitivity in the investigation of this important class of artists' colorants.

The identification of natural dyes found in archaeological objects and in works of art as textile dyes and lake pigments is a demanding analytical task. To address the problems raised by the very low dye content of dyed fibers and lake pigments, and by the requirement to remove only microscopic samples, surface enhanced Raman scattering techniques were investigated for application to museum objects. SERS gives excellent results with the majority of natural dyes, including: alizarin, purpurin, laccaic acid, carminic acid, kermesic acid, shikonin, juglone, lawsone, brazilin and brazilein, haematoxylin and haematein, fisetin, quercitrin, quercetin, rutin, and morin. In this study, limits of detection were determined for representative dyes and different SERS supports such as citrate reduced Ag colloid and silver nanoisland films. SERS was successfully used to identify natural madder in a microscopic fragment from a severely degraded 11^th Century Byzantine textile recently excavated in Amorium, Turkey.

Surface-enhanced Raman scattering (SERS) was investigated for applications in the analysis of anthraquinone dyes used in works of art. Two SERS procedures were developed and evaluated with frequently used anthraquinone dyes, alizarin, carminic acid and lac dye. The first procedure involves the removal of a microscopic fragment containing alizarin from a painting, and a layer of silver nanoparticles was thermally evaporated directly on the fragment to induce SERS signal from alizarin. The applicability of this procedure for analyzing solid samples of color layer from paintings was discussed in detail. In the second procedure, a SERS-active substrate was prepared by spin-coating an alumina-nanoparticle layer onto a glass slide, followed by thermally evaporating a layer of silver nanoparticles on top of the alumina layer. Aliquots of dye solutions were delivered onto this substrate where intense SERS spectra characteristic of alizarin, carminic acid, and lac dye were obtained. The effects of two parameters, the concentration of the alumina suspension, and the thickness of the silver nanoparticle layer, on the performance of the Ag-Al₂O₃ substrate were examined with alizarin as the model compound. Comparative studies with other common SERS substrates showed larger enhancement and improved reproducibility for the Ag-Al₂O₃ substrate. The potential applicability of the Ag-Al₂O₃ substrate for the analysis of real artifact objects was illustrated by the identification of alizarin extracted from a small piece of textile dyed with traditional methods and materials. The limit of detection for alizarin was estimated to be 7×10^-15 g from tests using solutions of known concentration.

Polycrystalline MFI zeolite thin films have been grown on the surface of optical fibers by in-situ crystallization method. The zeolite-coated optical fibers were investigated for detection of trace organic compounds in gas and liquid phases. The reflectivity of the zeolite-coated fibers responded to the change in organic concentration monotonically and reversibly. The effect of zeolite material chemistry of the zeolite crystals on the sensor behavior was also studied.

Aerosol particles with sub-micro meter size inhaled into respiratory systems cause serious damage to human body. In order to evaluate the health effects of the particles, classification methods of the particles with size and mass are needed. Several measurement methods of the particle size are established. However, conventional mass measurement methods are not enough to measure the particles with sub- pico gram. We propose a new mass measurement method of the aerosol particles based on laser trapping. In this method, an optically trapped silica particle is used as a measuring probe particle. The probe particle is trapped at a beam waist of the focused laser light and is forced to vibrate by deflecting the beam waist using AOD. The vibrating probe particle has a resonance frequency because it is governed by the spring-mass-damper system. When an aerosol particle is attached to the probe particle, the resonance frequency shifts according to the increase of the total mass. The mass of the aerosol particle can be measured from the shift of the resonance frequency. Experimentally, it is confirmed that the probe particle is governed by the spring-mass-damper system and has a resonance frequency. When a silica fine particle of 3pg in mass used as an aerosol particle is attached to the probe particle, the resonance frequency shift occurs as expected in the dynamic system and the fine particle mass can be measured based on the proposed method.

OPTRA has developed a new approach to the determination of particulate size distribution from a measured, composite, laser angular scatter pattern. Drawing from the field of infrared spectroscopy, OPTRA has employed a multicomponent analysis technique which uniquely recognizes patterns associated with each particle size "bin" over a broad range of sizes. The technique is particularly appropriate for overlapping patterns where large signals are potentially obscuring weak ones. OPTRA has also investigated a method for accurately training the algorithms without the use of representative particles for any given application. This streamlined calibration applies a one-time measured "instrument function" to theoretical Mie patterns to create the training data for the algorithms. OPTRA has demonstrated this algorithmic technique on a compact, rugged, laser scatter sensor head we developed for gas turbine engine emissions measurements. The sensor contains a miniature violet solid state laser and an array of silicon photodiodes, both of which are commercial off the shelf. The algorithmic technique can also be used with any commercially available laser scatter system.

The major trends driving optical chemical sensor technology are miniaturisation and multi-parameter functionality on a single platform (so-called multi-analyte sensing). A multi-analyte sensor chip device based on miniature waveguide structures, porous sensor materials and compact optoelectronic components has been developed. One of the major challenges in fluorescence-based optical sensor design is the efficient capture of emitted fluorescence from a fluorophore and the effective detection of the signal. In this work, the sensor platform has been fabricated using poly(methyl methacrylate), PMMA, as the waveguide material. These platforms employ a novel optical configuration along with rapid prototyping technology, which facilitates the production of an effective sensor platform. Sensing films for oxygen, carbon dioxide and humidity have been developed. These films consist of a fluorescent indicator dye entrapped in a porous immobilisation matrix. The analyte diffuses through the porous matrix and reacts with the indicator dye, causing changes in the detected fluorescence. The reaction between the dye and the analyte is completely reversible with no degradation of the signal after detection of different concentrations of the analyte. A single LED excitation source is used for all three analytes, and the sensor platform is housed in a compact unit containing the excitation source, filters and detector. The simultaneous detection of several analytes is a major requirement for fields such as food packaging, environmental quality control and biomedical diagnostics. The current sensor chip is designed for use in indoor air-quality monitoring.

Optical Bragg grating sensors based on side polished or etched waveguides have been demonstrated for the measurement of refractive index [1, 2, 3, 4]. However, these devices typically exhibit polarization dependent behavior for index values around 1.3. In this report, a ridge waveguide Bragg grating (WBG) sensor with high sensitivity, for refractive index measurement in liquids is presented. The device is based on a small core size silica open top cladding ridge waveguide and polarization independent Bragg gratings (PIBG) written and optimized using UV light [5,6,7]. The WBG is surrounded by a liquid analyte and is accessed via evanescent field interaction of the guided waveguide mode with the liquid layer. In the theoretical analysis, enhancement of sensitivity by optimizing waveguide structures is proposed. In the experiment, Bragg grating is induced in the open top cladding ridge waveguide using a phase mask and excimer laser radiation at 193 nm. A series of refractive index matching liquids are used to test the device. Results indicate the sensitivity is as high as 50 pm of wavelength shift for a change of the index 3×10^-4. This technology can offer many advantages over previously proposed waveguide sensors, including enhanced sensitivity, and dynamic measurement range, better polarization stability, and a simpler fabrication processes.

A pattern classification system for the identification of UV-visible synchronous fluorescence of petroleum oils is developed. The system is a composite of three phases, namely, feature extraction, feature selection and pattern classification. These phases are briefly described, focusing particularly on the classification method. A method called successive feature elimination process (SFEP) is used for feature selection and a proximity index classifier (PIC) is developed for classification. The feature selection method extracts as many features from spectra as conveniently possible and then applies the SFEP process to remove the redundant features. From the remaining features a significantly smaller feature subset is selected that enhances the recognition performance of the PIC classifier. The SFEP and PIC methods are formally described. These methods are successfully applied to the classification of UV-visible synchronous fluorescence spectra. The features selected by the algorithm are used to classify twenty different sets of petroleum oils. The system was trained on the design set on which the recognition performance was 100%. The performance on the testing set was over 93% by successfully identifying 28 out of 30 samples in six classes. This performance is very encouraging. In addition, the method is computationally inexpensive and is equally useful for large data set problems as it always partitions the problem into a set of two class problems.