This PDF file contains the front matter associated with SPIE Proceedings Volume 6585, including the Title Page, Copyright information, Table of Contents, and the Conference Committee listing.

We report on the design of micro-ring resonator optical sensors for integration on what we call optical printed circuit boards (O-PCBs). The objective is to realize application-specific O-PCBs, either on hard board or on flexible board, by integrating micro/nano-scale optical sensors for compact, light-weight, low-energy, high-speed, intelligent, and environmentally friendly processing of information. The O-PCBs consist of two-dimensional planar arrays of micro/nano-scale optical wires, circuits and devices that are interconnected and integrated to perform the functions of sensing and then storing, transporting, processing, switching, routing and distributing optical signals that have been collected by means of sensors. For fabrication, the polymer and organic optical wires and waveguides are first fabricated on a board and are used to interconnect and integrate sensors and other micro/ nano-scale photonic devices. Here, in our study, we focus on the sensors based on the micro-ring structures. We designed bio-sensors using silicon based micro-ring resonator. We investigate the characteristics such as sensitivity and selectivity (or quality factor) of micro-ring resonator for their use in bio-sensing application. We performed simulation studies on the quality factor of micro-ring resonators by varying the radius of the ring resonators and the separation between adjacent waveguides. We introduce the effective coupling coefficient as a realistic value to describe the strength of the coupling in micro-ring resonators.

A red VCSEL illuminator module demonstrator was manufactured by injection moulding integration. A red VCSEL chip was first attached to a simple FR4 substrate, which contains bonding pads and conducting wires for the VCSEL chip attachment and electrical driving. The substrate was then placed as an insert in an injection mould. The VCSEL chip shielding and optics formation was made in a one-step injection moulding process. The used optical thermoplastic in the processing was polycarbonate (PC). The pursued optical function of the single spherical surface attained in the moulding was to collimate the emitted red light (&lgr;=664.5 nm) from the VCSEL chip. The main critical issue related to the manufacturing of the illuminator module in the injection moulding process was the durability of bonding wire contacts. A single 25 &mgr;m diameter gold wire was used in wire bonding in order to create the upper contact to the chip. The lower contact was processed by attaching the chip to the substrate using conductive epoxy. A test series of 20 modules using FR4 substrate materials were produced. The number of fully operative modules was 12 resulting total module yield of 60%. The main reason for a non-operative module was loosening of the bonding wire during the injection moulding process. The bonding wire durability in the moulding process can be improved by using glob-top shielding of the VCSEL device before injection moulding and using a lower holding pressure in the injection moulding process. A diamond turned insert was used in the mould in order to create a high quality lens surface on the top of the VCSEL chip. The tower average length after one iteration round by mould modification was 8.676 &mgr;m, so the measured value was on average 20 &mgr;m larger than nominal value. The measured RMS roughness of the processed lens surface was 5 ... 7 nm and the radius -3.23 ... 3.83 mm. The radius of the lens and the length of the tower varied depending of the used process parameters. The manufactured illumination module can be integrated with a CMOS image matrix sensor in order to form a compact hologram reader system. The injection moulding integration principle seems to be very promising method to manufacture intelligently integrated and cost-effective optoelectronic products according to experience with this demonstrator.

InAs and InAs(Sb)(P) based heterostructures with InAsSbP claddings grown onto heavily doped or undoped n-InAs substrates have been processed into 230÷430 &mgr;m wide mesa flip-chip devices operating in the 3÷5 &mgr;m spectral range. We present temperature dependence of I-V, R_oA, S_I and D^* as well as the dependence on a photon energy in uncoated backside illuminated and equipped with an immersion lens photodiodes respectively. Room temperature D^*&lgr; as high as (1.75x10¹¹÷3x10⁸) cmHz1/2W^-1 was achieved in photodiodes with Si lens having effective diameter of 3.3 mm and operating in the 3÷5 &mgr;m range correspondingly.

Metal-Semiconductor-Metal photodiodes were fabricated on epitaxially grown Al_xGa_1-xN on Si(111). The Aluminium content of the layers grown by means of molecular beam epitaxy (MBE) was 50, 80 and 100%, respectively. The processing was performed by standard microelectronic fabrication techniques like photolithography, wet and dry etching (RIE) and physical and chemical vapor deposition (PVD,CVD). The devices were characterized under illumination in a wavelength range from 400 to 185nm to determine the cut-off wavelength defined by the band-gap energy. Typical figures of merit like spectral responsivity R quantum efficiency &eegr; and specific detectivity D* have been extracted from the measurement data.

The optical analyzers used in on-line and off-line process measurements set a large variety of special demands for optical detectors, i.e. customized detectors are needed. Both the detector (array) and its read-out circuit are affected. The typical volume for process analyzers is so low that fully customized ASICs easily become too expensive for signal recovery solutions in optical detectors. This is due to high fixed costs in ASIC development. Low Temperature Co-fired Ceramics (LTCC) substrates allow high integration grade and the smart packaging solutions needed in optical detectors. The ceramic substrate is suitable for hermetic packaging. The high integration grade is possible thanks to multilayer capability, with narrow metal strips as well as blind and buried vias which can be placed directly underneath the solder pads. Standard connection methods can be used, i.e. soldering, gluing and wire bonding for components and detector chip assembly. By using small passive components and bare chip or chip scale packaged active components, one is able to integrate the read-out functions in a small enough space. This paper briefly presents three different cases where infrared photoconductive detector arrays are attached to read-out circuitry which is made on LTCC substrate. The detector read-out hybrids are packaged in hermetic metal packages. The packages have been either non-cooled or thermoelectrically cooled. 24 element PbS, 4 by 4 element PbS and 128 element MCT cases are handled. Also an example of an integrated infrared light emitting diode array for an LED-spectrometer is presented. General feasibility analysis, including some electrical test results and the management of substrate dimensional tolerances, is given.

A microscope add-on device to a 1.3 Mpix camera phone was selected as a demonstrator system for testing inmould integration of electronic substrates and plastic optics. Optical design of the device was quite challenging due to the fact that illumination system needed to be integrated with a double aspheric singlet lens structure as a single optical piece. The designed imaging lens resolution was adequate to resolve 10 &mgr;m features with a mobile phone camera. In the illumination optics the light from LEDs embedded into the plastic structure was collected and guided to the surface that was imaged. Illumination was designed to be uniform and adequately bright to achieve high resolution images with the camera phone. Lens mould design was tested by using injection moulding simulation software. The critical mould optical surfaces were designed as separate insert parts. Final shapes producing lens surfaces were tooled by diamond turning on nickel coatings. Electronic circuit board inserts with bonded bare LED chips and packaged SMD LEDs were assembled to the mould and then overmoulded with optical grade PMMA. Experiences proved that inmould integration of electronic substrates, bare LED chips and high resolution imaging optics in injection-compression moulding process is feasible. The yield of embedded packaged and also bare chip components was close to 100% after the right injection moulding process parameters were found. Prototype add-on system was characterized by testing the imaging properties of the device with a camera phone.

Integrated optical devices offer dense, multifunctional capability in a single robust package but are rarely considered compatible with the fields of remote or distributed sensing or compete in the long-haul with conventional 'one-dimensional' fibers. Here we aim to change that by introducing a 'flat-fiber' process that combines the advantages of of existing low-cost fiber drawing with the functionality of planar lightwave circuits in a novel hybrid format. Adapted from MCVD fiber fabrication, our preforms are deposited and collapsed into a rectangular geometry before drawing, resulting in extended lengths of mechanically flexible flat-fiber material with a photosensitive germanium-doped planar core. Direct UV writing is then used to create arrays of channel waveguides within the core layer, using a 5μm focused laser spot that literally 'draws' refractive index patterns into the flat fiber as it moves. Having recently demonstrated simple building blocks for integrated optical circuits in millimeter-wide flat-fibers (including; channel waveguides, power junctions and splitters, and planar Bragg gratings), our next step is to incorporate structured windows at strategic points along the fiber to allow fluidic access to the evanescent field for local refractive-index-based chemical measurements. By taking this approach, we hope to extend beyond the limitations of traditional planar and fiber substrates, allowing exotic material compositions, device layouts, and local sensing functions to be distributed over extended distances with no coupling or compatibility concerns in highly functional distributed lab-on-a-chip devices.

Theoretical analysis and experimental investigations are presented on the resolution of a ratiometric wavelength measurement system. Theoretical modelling indicates that the resolution of a ratiometric wavelength measurement system is determined by the signal-to-noise ratio of the input signal and the noise of the photodetectors associated with optical-to-electronic conversion. For the experimental verification, a ratiometric system employing a macrobending standard singlemode fiber is developed and corresponding results are in a good agreement with the theoretical prediction.

We propose an alternative design to the wavemeters based on scanning Michelson interferometers. Using realistic experimental parameters, we show that a relative accuracy of one part in 6x10^-8 can be reached with a displacement of the target mirror of only 360 &mgr;m. This improvment becomes possible thanks to the significant advances in polarimetry that permit measurement of the ellipsometric parameters &psgr; and &Dgr; with an accuracy of 0.07° with readily-available commercial equipment. This leads to an interpolation rate of &lgr;/10000. The proposed method has been setup and the chief parameters limiting its accuracy are determined.

The combination of fibre optics with micro- and nano-structure technologies offers great potential for the realisation of novel sensor concepts. Selected examples of advanced optical fibre sensor systems based on sub-wavelength structured components will be presented. Such examples are highly sensitive extrinsic fibre-optic humidity and hydrocarbon sensors for application in gas industry and in environmental monitoring using nano-porous thin-film Fabry-Perot transducer elements, or intrinsic fibre Bragg grating sensor networks for structural health monitoring (i.e., monitoring mechanical strain and deformation, vibration, temperature) in electric power facilities, aerospace, railways and geotechnical engineering as well as for chemical detection (e.g., hydrogen). Additionally, new concepts for chemical and biochemical sensing applying plasmonic metal nano-particles, photonic crystal fibres, and optical nano-wires will be discussed.

Birefringence in fiber Bragg gratings (FBGs) can result from two distinct effects that combine with the intrinsic fiber birefringence: the birefringence induced by the UV photo-writing and the birefringence due to a transversal load. In both cases, it leads to polarization dependent loss (PDL) and differential group delay (DGD) inside gratings. Although these parameters are not desired for optical telecommunications applications, we demonstrate here that they can be advantageously used to obtain temperature-insensitive transverse strain measurements with uniform FBGs written into standard single mode fiber, which is not possible through conventional amplitude spectral measurements. Simulated results obtained by means of the coupled mode theory and the Jones formalism as well as experimental results measured by means of a tunable laser source and a polarimeter are presented.

The use of fibre Bragg grating sensors to study mortars' dimensional variations during the setting process is reported. When determining a mortar's potential to fissure, it's important to know its total retraction. This means it is necessary to know not only the mortar's retraction after hardened, but also to know how much it retracts during the plastic phase. This work presents a technique which allows to measure dimensional variations, either expansion or retraction, during the whole setting process. Temperature and strain evolution during both plastic and hardened phase of the mortar were obtained, allowing the determination of dimensional variations and setting times. Due to its high-speed, ease of implementation and low operation costs, this technique will allow to get a deeper knowledge of the effects of several additives on the mortar's behaviour, allowing to improve its mechanical properties through the determination of the proper chemical composition.

This paper discusses a new sensor design based on optical fibre Bragg gratings which is being developed in the framework of the MASSFOS-project ('Multi-Axial Stress and Strain sensing of thermo hardened composite elements using Fibre Optic Sensors'-project). The objective of this ESA co-funded project is to develop a monitoring system which measures dynamically the multi-axial stress and strain plus temperature in thermo hardened composite elements. The sensor consists of a 'High Birefringence'-fibre in which two gratings have been inscribed; each grating yields two distinct Bragg peaks. The first grating is sensitive to the total stress field in the material, while the second one is isolated from transverse stress components. By measuring the four Bragg peaks of the sensor, it is theoretically possible to determine the total strain field, plus the temperature inside a composite material. Static experiments (a tensile test and a compressive test) have already been carried out to prove the feasibility of the sensor embedded in a composite laminate.

Long-period gratings (LPGs) in an optical fiber, which was designed and fabricated for achieving high insensitivity of the inscribed LPGs both to bending and to the external index of refraction, are investigated. The fiber has a double cladding, consisting of a uniform outer cladding and a graded-index inner cladding, where the index of refraction decreases approximately parabolically with radius. This fiber is referred to as the parabolic-index cladding (PIC) fiber. Results obtained in the preparation of preforms and drawing PIC fibers are given. The theoretical analysis, carried out by the mode expansion and beam propagation method, yields field distributions and effective indexes of the fundamental core mode LP₀₁ and several low-order circularly symmetric cladding modes LP_0m for several external indexes of refraction. Experiments are done with an LPG with a period of 214 μm inscribed with a CO₂ laser in the PIC fiber. In experiments, transmission spectra of the LPG immersed in three liquids with refractive indexes in a relatively wide range around the index of silica (water, silica-index-matching liquid, silicone oil) are measured in a temperature range of 25-67.5°C. From experiments it follows, in agreement with the theoretical analysis, that the spectral positions of the investigated attenuation band at &lgr; ≈ 1550 nm (coupling between the LP₀₁ and LP₀₂ mode), determined at temperatures in the above range, are highly insensitive to the external index of refraction.

We present preliminary results of the tests performed by using a modular fiber-optic sensor for hydrostatic pressure/temperature and also rotation measurements envisaged for refinery applications. Our prototype fiber optic sensor for rotation measurements has been successfully installed and tested in the ORLEN Refinery in Plock, Poland. During the initial tests, we used rotating machine to measure its rotor velocity. As a light source we used a pigtailed laser diode (λ=635 nm) whereas the sensor head was connected to the light source and to a detector by a 100-meters-long loop of the multimode optical fibers. The output characteristics of the modular sensing system have been optimized in view of enhancing their measurement capabilities and in order to minimize disturbing environmental effects.

Tactile sensors are needed for many emerging robotic and telepresence applications such as keyhole surgery and robot operation in unstructured environments. We have proposed and demonstrated a tactile sensor consisting of a fibre Bragg grating embedded in a polymer "finger". When the sensor is placed in contact with a surface and translated tangentially across it measurements on the changes in the reflectivity spectrum of the grating provide a measurement of the spatial distribution of forces perpendicular to the surface and thus, through the elasticity of the polymer material, to the surface roughness. Using a sensor fabricated from a Poly Siloxane polymer (Methyl Vinyl Silicone rubber) spherical cap 50 mm in diameter, 6 mm deep with an embedded 10 mm long Bragg grating we have characterised the first and second moment of the grating spectral response when scanned across triangular and semicircular periodic structures both with a modulation depth of 1 mm and a period of 2 mm. The results clearly distinguish the periodicity of the surface structure and the differences between the two different surface profiles. For the triangular structure a central wavelength modulation of 4 pm is observed and includes a fourth harmonic component, the spectral width is modulated by 25 pm. Although crude in comparison to human senses these results clearly shown the potential of such a sensor for tactile imaging and we expect that with further development in optimising both the grating and polymer "finger" properties a much increased sensitivity and spatial resolution is achievable.

Single crystal Silicon Carbide (SiC) chip operations for a proposed wireless temperature sensor are evaluated for various power plant industrial conditions such as soot levels, chemical exposure, and changes in polarization.

One of the most promising projects for the new definition of the kilogram is the watt balance. It uses a two-mode procedure: static mode and dynamic mode. One of the key points is to control the velocity, the yaw and the pitch of a moving coil during the dynamic mode. We have developed a specific method based on the use of a homemade double pass heterodyne interferometer, a two-level translation stage, and a home-made high frequency phase shifting electronic circuit. This system will replace the commercial heterodyne system (laser head and interferometer) used at present time which is limited in power and has polarization limitations. In this paper, we propose a novel and specific heterodyne interferometer able to ensure all previous demands to control the displacements of the moving coil in order to reduce the velocity noise. The laser source is powerful enough to ensure multiple measurements axis. The laser is frequency stabilized on iodine atomic transition around &lgr;=532 nm to ensure traceability. All the polarization defaults of the classical heterodyne interferometer have been minimized in order to reduce non-linearity effects. The most original point is that the reference beam is locked on an external electronic reference, which allows to be less sensitive to vibration and polarization defects of optical components from the laser head to the vacuum enclosure where the interferometer is placed.

Integrated optics (IO) technology has been primarily used in optical communication applications but it is expanding fast into the field of optical sensing. In this work we report the fabrication of integrated devices using hybrid sol-gel technology and in particular its application in the fabrication of a refractive index integrated sensor based in a Mach-Zehnder interferometric configuration. In one of the interferometer arms, a analysis chamber is created by exposing the waveguide through the removal of the device cladding. On the same arm, two Bragg gratings with the same period are fabricated: one in the unprotected waveguide area and another in close proximity (cladded area); because of the different effective index in the two grating regions, two peaks are observed in reflection if the device is tested with a broadband source. Any change of the refractive index of the material filling the analysis chamber can be detected in two ways: by measuring the intensity of the interferometric output (at a wavelength different from the Bragg wavelength of the two gratings) or by measuring the spectrum of the reflected signal. The high sensitivity is obtained by measuring the interferometric output, while the high dynamic range can be achieved by measuring the reflected signal from the grating structures.

In this work, an integrated optical microsystems for the continuous detection of flammable liquids has been fabricated and characterized. The proposed system is composed of a the transducer element, which is a vertical silicon/air Bragg mirror fabricated by silicon electrochemical micromachining, sealed with a cover glass anodically bonded on its top. The device has been optically characterized in presence of liquid substances of environmental interest, such as ethanol and isopropanol. The preliminary experimental results are in good agreement with the theoretical calculations and show the possibility to use the device as an optical sensor based on the change of its reflectivity spectrum.

UV written planar waveguide sensors provide an integrated solution to refractive index sensors. The high sensitivity of the devices originate from their use of Bragg gratings which provide an accurate means of interrogating the local effective index. Conventionally the optical mode is made sensitive to an external refractive index by etching away the cladding and exposing it to an analyte. These devices have been used to sense liquid/solid phase changes and have displayed their potential for use as biological and chemical sensors. Recent results demonstrate sensitivities rivaling that of the highest specification Surface Plasmon Resonance (SPR) techniques. Here we introduce a new geometry which embraces the benefits of planar technology to realise new integrated devices. The geometry relies upon the use of a vertical trench or groove to produce an interface of optical quality which provides lateral access for an optical mode. The evanescent field interacts with the material within the groove and a Bragg grating in the region provides the means for interrogation. This reorientation of the sensor geometry provides additional flexibility to UV written devices, allowing several different sensors to be defined on the single substrate without multiple etching processes. These multiple sensors may offer complementary information such as the effective index as a function of penetration depth and interrogation wavelength for dispersion analysis. The paper also outlines the inherent feature benefits and fabrication advantages, including a reduction in return loss, spectral artefacts and stress induced birefringence.

TE waves can propagate in metal film of three waveguide structure if at least one of the covering media is nonlinear. The waveguide sensor under consideration consists of a metal wave guiding film coated with two nonlinear claddings. Contrary to what has been recently predicted, it is shown here that uniform field profile may be achieved under the suitable choice of the dielectric constants of the surroundings. Electric fields and fraction of power flow down the sensor layers are studied here. We expect this kind of planar waveguide sensors may be realized experimentally and will have applications in future opto-electronic devices. Uniform field approach has been discussed and implemented for the first time in investigating the waveguide sensors.

Implementation of a strain tuned linear cavity EDF laser for interrogation of multiplexed FBG sensors is reported. A high-strength draw-tower FBG is used as the mechanically tunable element allowing for the wavelength sweeping of the laser. A simple algorithm to process the noisy acquired data and identify the peak of the FBG sensors spectra is proposed. These two techniques are able to improve the reliability of multiplexed FBG interrogation systems using mechanically tunable FBG and decrease the cost of systems that use conventional tuning elements in the optical circuit.

In order to identify defects of the electrical infrastructure during train operation, a fiber Bragg grating based sensor system performs measurements of the distribution of short time force changes in vertical and horizontal (driving) direction between current collector and overhead contact line. The actual model calculations and the practical design of a 2-dimensionally arranged strain sensor network have been especially enhanced to the calculation of impact directions. The well-known advantages of fiber-optic sensors - embedding capability in the composite carbon/aluminum collector strip, multiplexing of distributed sensor networks, electrical isolation - are of particular importance for detection and characterization of fast impacts immediately at the position of incidence. Tests under everyday operating conditions with trains on high-speed tracks as well as under high load in mountain regions proved the application of this sensing technology. Problems and solutions for the sensor network embedment, the fast Bragg sensor interrogation algorithms, and actual lab test results with their application-orientated analysis will be presented.

With hyperspectral pushbroom imaging spectrometers on Earth observation satellites it is possible to detect and identify dedicated ground pixels by their spectral signature. Conventional time consuming on-ground processing performs this selection by processing the measured hyperspectral data cube of the image. The Imaging Spectral Signature Instrument (ISSI) concept combines an optical on-board processing of the hyperspectral data cube with a thresholding algorithm, to identify pixels with a pre-defined and programmable spectral signature, such as water, forest and minerals, in the ground swath. The Imaging Spectral Signature Instrument consists of an imaging telescope, which images an object line on the entrance slit of a first imaging spectrometer, which disperses each pixel of the object line into its spectral content and images the hyperspectral image on the spatial light modulator. This spatial light modulator will be programmed with a spatial transmission or reflection behavior, which is constant along the spatial pixels and along the spectral pixels identical to a filter vector that corresponds to the spectral signature of the searched specific feature. A second inverted spectrometer reimages the by the first spectrometer dispersed and by the spatial light modulator transmitted or reflected flux into a line of pixels. In case the spectral content of the ground scene is identical to the searched signature, the flux traversing or reflecting the spatial light modulator will be maximum. The related pixel can be identified in the final image as a high signal by a threshold discriminator. A component test setup consists of an imaging lens, two Imspector™ spectrographs, a spatial light modulator, which is a programmable transmissible liquid crystal display and a CCD sensor as a detector. A mathematical model was developed for the instrument and its performance was evaluated in order to compare different concept variations. All components were measured and characterized individually, and the results were used in the simulations. Performance was then analyzed by means of radiometric throughput and spatial and spectral resolutions. The simulations were performed at wavelengths of 450 nm to 900 nm. The throughput was found to be between 1% and 4.5%.

Classical triangulation sensors are wildly used but they have some typical drawbacks. The measurement result depends always on the angular orientation of the sensor what can be especially troublesome at steps or gaps. To eliminate this disadvantage of the classical triangulation we introduced in [1] a new kind of optical triangulation - the rotationally symmetric triangulation sensor. Therefore the measurement result depends not any longer on the angular orientation of the sensor. This is achieved by imaging the scattered light from an illuminated object point to a centered and sharp ring on a low cost area detector. The diameter of the ring is proportional to the distance of the object. The theoretical limit of the measurement uncertainty of the rotationally symmetric triangulation sensor is 3 to 4 times lower than the limit of the classical triangulation [2] for comparable and application oriented designs, because a complete ring is used for distance evaluation instead of only a point. In this contribution we show for the first time a design and a corresponding hardware which is completely realized by two toriodal formed aspherical plastic lenses. These lenses can be manufactured by injection molding for approximately the same costs than ordinary aspherical plastic lenses. So it is possible to realize this new sensor for the same price than a classical triangulation sensor but with higher accuracy and a much better robustness. For the rotationally symmetric triangulation sensor a standard 2D detector is used, the same detector like in standard vision systems. Additionally it is stressed that close to the axis of toriodal lenses is enough available design space to add a second optical system to image the object. The toriodal lenses allow to realize a retrofocus typ of imaging system without increasing the number of optical elements. However, in the middle of the lenses the surfaces are used for imaging and on the outer section they are used for triangulation. These two multipurpose optical elements can still be manufactured by injection moulding. To summarize, we show a low cost system with only one standard 2D detector and two aspheric lenses that realizes two tasks, i.e. imaging the object on the detector and distance measurement by rotationally symmetric triangulation.

Authors propose a new approach in displacement measurements based on Gaussian beam propagation, their focusing properties and their spatial modulation. Two modulated Gaussian beams with a phase shift of 180° are focused on a slit fixed to the moveable object. The resulting laser beams at the slit output are focused into a multimode fiber. A lock-in amplifier demodulates the photodiode signal placed at the multimode fiber output. The lock in-amplifier output signal is a function of the slit displacement. The sensor is completely fibered with no electrical wires so it presents no heat dissipation near the moveable object and is compatible with vacuum use. It is a contactless sensor and provides a simple compact design and cost-effective means of achieving high resolution absolute displacement measurements. The preliminary experimental data of the sensor calibration by laser interferometry have shown a resolution of 0.1 nm.

The paper discusses problems of Silicon wafer measurements accuracy in context of the scanning helium atom microscope, which is a new technique currently under development. In the microscope the helium atom beam is used as a probe. The overall microscope resolution depends on a deflecting element, which shapes the beam and focuses it onto a sample's surface. The most promising focusing component appears to be an ultra thin silicon wafer that is deformed under a precise electric field. Thus its quality is decisive for the project success. Flatness and thickness uniformity of the wafer must be measured in order to select the best plate to be used in the microscope. A scanning measurement system consists of two coaxially positioned confocal heads. Recent studies have revealed that the system is very sensitive to temperature variation. The compensation algorithms and further measures designed to suppress the temperature effect are presented and discussed.

Aptamers are single stranded DNA or RNA ligands which can be selected for different targets starting from a library of molecules containing randomly created sequences. Aptamers have been selected to bind very different targets, from proteins to small organic dyes. Aptamers are proposed as alternatives to antibodies as biorecognition elements in analytical devices with ever increasing frequency. This in order to satisfy the demand for quick, cheap, simple and highly reproducible analytical devices, especially for protein detection in the medical field or for the detection of smaller molecules in environmental and food analysis. In our recent experience, DNA and RNA aptamers, specific for three different proteins (Tat, IgE and thrombin), have been exploited as bio-recognition elements to develop specific biosensors (aptasensors). These recognition elements have been coupled to piezoelectric quartz crystals and surface plasmon resonance (SPR) devices as transducers where the aptamers have been immobilized on the gold surface of the crystals electrodes or on SPR chips, respectively.

In this work novel 5,10,15,20 meso-tetraphenyl porphyrin (H₂TPP) films have been deposited by means of a new physical technique named glow discharge induced sublimation (GDS). A preliminary characterization has been performed by means of scanning electron microscopy (SEM) and Fourier transform infra-red (FT-IR) analyses. SEM images and infra-red analyses highlight the great surface roughness and the high purity of GDS films, respectively. For comparison, H₂TPP films have been also deposited by means of spin coating (SPIN) technique. Optical sensing measurements, performed in differently concentrated ethyl alcohol (EtOH) atmospheres, highlight that GDS samples yield higher response intensities than SPIN films, very short response times and complete recovery.

The paper shows an approach to the determination of pH changes of solutions with a fine spatial resolution by means of fiber-optic tapers and fluorescence detection. This approach can be adopted for the determination of auxin flow through celluar membranes. Spectral absorption and fluorescence of pH transducers, namely of fluorescein, carboxyfluorescein, 6,8-dihydroxy-1,3-pyrenedisulfonic acid disodium salt and 2',7'-bis(2-carbonylethyl)-5(6)-carboxyfluorescein, were tested. The approach, based on the determination of a shift of the maxima of their fluorescence peaks, was employed for processing the measured fluorescence data in bulk solutions. Suitable tapered fiber probes were prepared and in vitro demonstrated for pH monitoring in a pH range from 6 to 7.

The control of chlorine content in water is an important issue in water treatment. This paper presents an opto-electrochemical approach to the detection of chlorine in water. In this approach, optical changes of a sensing layer caused by its interaction with chlorine are electrically reversed by using a thin conductive and transparent layer of Indium-Tin-Oxide (ITO) deposited in between an optical substrate and the sensing layer acting as an electrode. The paper deals with the preparation and characterization of sensing layers based on commercially available transducers suitable for the detection of chlorine in water and applicable on ITO-coated planar substrates and/or silica optical fibers. Sensing layers of several absorption and luminescent transducers were applied onto ITO layers deposited on planar glass or fiber-optic substrates by electropolymerization or by the sol-gel method. The best response was observed from o-phenylenediamine and polyluminol layers prepared by electropolymerization. The sensitivity and limit of detection of a polyluminol layers are comparable to hygienic limits for the chlorination of water. The parameters of o-phenylenediamine layers obtained up to now are close to these values. A damaging effect of chlorine in higher concentrations on the sensing layers was observed.

Atypical physiological symptoms can be developed in healthy people under critically ill conditions. pH, pO₂ and pCO₂ are informative indicators of the conditions of a living system and can be valuable in determining the physiologic status of the critically ill patients. The continuous monitoring of these small molecules into the interstitial fluid (ISF) is a promising approach to reduce diagnostic blood loss and painful stress associated with blood sampling. Microdialysis is the approach followed for the extraction of the sample from the subcutaneous adipose tissue; the drawn interstitial fluid flows through a microfluidic circuit formed by the microdialysis catheter in series with a glass capillary on the internal wall of which the appropriate chemistry for sensing is immobilised. Absorption changes for pH sensor and modulation of the fluorescence lifetime for pO₂ and pCO₂ are the working principle. Phenol red covalently bound into the internal wall of a glass capillary by means of the Mannich reaction and platinum(II) tetrakis-pentafluorophenyl-porphyrine entrapped within a polymerised polystyrene layer are the chemical transducers used for pH and oxygen detection; the ion pair 8- hydroxypyrene-1,3,6-trisulfonic acid trisodium salt/ tetraoctylammonium hydroxide, dissolved in a silicon-based polymeric matrix, is used for the carbon dioxide detection. A suitable hemorrhagic shock model was developed in order to validate clinically the developed sensors in the condition of extreme stress and the obtained results show that the adipose tissue can become an alternative site for the continuous oitoring of pH, pO₂ and pCO₂.

The paper presents new experimental results on the sensitivity of three types of microstructure fibers (MSFs) modified by xerogel layers to aromatic hydrocarbons, namely to toluene. MSFs with air holes with diameters in a range 10 - 50 &mgr;m, arranged in one, two or three rings, were prepared and their segments were used in sensing experiments. Capillary silica fibers (CFs) were also fabricated for reference sensing measurements. Segments of the fabricated MSFs and CFs were modified by thin xerogel layers applied onto the hole walls by the sol-gel method from sols based on tetraethoxysilane or methyltriethoxysilane. For sensing experiments, the segments were fixed in a special cell making it possible to control the excitation of the fiber and flow of gaseous chemicals through the air holes. The sensitivity of the MSFs and SCFs to gaseous mixtures of toluene in nitrogen was determined from spectral changes of the output light from the fibers in a range of 1600-1800 nm. Experimental results show that the sensitivity of MSFs depends on their architecture, particularly on the arrangement, diameters and number of air holes. A detection limit of about 0.007 vol.% of toluene has been achieved.

In this paper, we present a novel hydrogen sensor based on a fiber Bragg grating covered by a catalytic sensitive layer. In presence of hydrogen in air, an exothermic reaction occurs in the sensitive layer made of a ceramic doped with noble metal. This chemical reaction leads to an increase of temperature around the fiber Bragg grating, which consequently shifts the Bragg wavelength. The sensing mechanism is thus simply based on the monitoring of the Bragg wavelength shift. The sensor response is linear and without hysteresis between increasing and decreasing hydrogen concentrations. It is also selective and extremely fast. Different experiments obtained on uniform fiber Bragg gratings of different physical lengths are reported in this paper.

The paper concerns the results of optical fibre's ultraviolet sensors' investigation. The cladding of the optical fibre's sensing part was removed and substituted with an active layer containing a coumarin's derivative designated with the number 3609. The dye acted as a transducer converting ultraviolet into visible radiation which could be easily detected. The theoretical modeling with the use of genetic algorithms proved that the best sensitivity of the sensor is achieved when the refractive indices of the active layer and the core are equal. Organically Modified Silica (ORMOSIL) matrices satisfy that condition as their refractive indices may be controlled and reach a value characteristic for the fused silica glass. However it may be expected that both the structure and the composition of ORMOSIL matrices may influence the organic dye's behaviour. The aim of the experiment presented in the paper was to measure the sensitivity of optical fibre sensors comprising the active layers composed of three alkoxysilanes which were methyltriethoxysilane (MTES), phenyltriethoxysilane (PhTES) and tetraethoxysilane (TEOS) as far as the sensitivity of the sensors with silica active layer derived from pure TEOS. Moreover, the influence of hydrolysis and condensation's time on the intensity of dye's luminescence both in active layers and sols' solutions was investigated. The results proved that hydrolysis time and gel's composition may influence a sensitivity of the sensor. Despite the initial decrease of luminescence's signal the long-lasting stability of UV/VIS conversion has been noticed which creates a possibility of the future practical application of the described sensors.

A novel concept of noninvasive monitoring of human tissue and blood based on optical diffuse reflective spectroscopy combined with metabolic heat measurements has been under development. A compact integrated fiber optical and thermal sensor has been developed. The idea of the method was to evaluate by optical spectroscopy haemoglobin and derivative concentrations and supplement with data associated with the oxidative metabolism of glucose. Body heat generated by glucose oxidation is based on the balance of capillary glucose and oxygen supply to the cells. The variation in glucose concentration is followed also by a difference from a distance (or depth) of scattered through the body radiation. So, blood glucose can be estimated by measuring the body heat and the oxygen supply. The sensor pickup contains of halogen lamp and LEDs combined with fiber optical bundle to deliver optical radiation inside and through the patient body, optical and thermal detectors. Fiber optical probe allows diffuse scattering measurement down to a depth of 2.5 mm in the skin including vascular system, which contributes to the control of the body temperature. The sensor pickup measures thermal generation, heat balance, blood flow rate, haemoglobin and derivative concentrations, environmental conditions. Multivariate statistical analysis was applied to convert various signals from the sensor pickup into physicochemical variables. By comparing the values from the noninvasive measurement with the venous plasma result, analytical functions for patient were obtained. Cluster analysis of patient groups was used to simplify a calibration procedure. Clinical testing of developed sensor is being performed.

We study changes in the polarization of a light induced by the interaction of light with a surface plasmon. Based on the results of the study, a novel polarization control scheme for surface plasmon resonance (SPR) sensors is proposed. Theoretical model of an SPR sensor employing the new polarization control scheme is presented. The theoretical analysis suggests that the proposed polarization control scheme can significantly improve sensitivity and operating range of SPR sensors. Results of the theoretical analysis are validated experimentally using a laboratory SPR imaging sensor system with the proposed polarization control.

Photonic induced immobilization of biosensor molecules is a novel technology that results in spatially oriented and spatially localized covalent coupling of a large variety of biomolecules onto thiol reactive surfaces, e.g. thiolated glass, quartz, gold or silicon. The reaction mechanism behind the reported new technology involves light-induced breakage of disulphide bridges in proteins upon UV illumination of nearby aromatic amino acids resulting in the formation of reactive molecules that will form covalent bonds with thiol reactive surfaces. This new technology has the potential of replacing present micro dispensing arraying technologies, where the size of the individual sensor spots are limited by the size of the dispensed droplets. Using light-induced immobilization the spatial resolution is defined by the area of the sensor surface that is illuminated by UV light and not by the physical size of the dispensed droplets of sensor molecules. This new technology allows for dense packing of different biomolecules on a surface, allowing the creation of multi-potent functionalized materials, such as biosensors with micrometer sized individual sensor spots. Thus, we have developed the necessary technology for preparing large protein arrays of enzymes and fragments of antibodies, with micrometer resolution, without the need for liquid micro dispensing.

The interaction between an analyte and a biological recognition system is normally detected in biosensors by the transducer element which converts the molecular event into a measurable effect, such as an electrical or optical signal. Porous silicon microstructures have unique optical and morphological properties that can be exploited in biosensing. The large specific surface area (even greater than 500 m²/cm³) and the resonant optical response allow detecting the effect of a change in refractive index of liquid solutions, which interact with the porous matrix, with very high sensitivity. Moreover, the porous silicon surface can be chemically modified to link the bioprobe which recognize the target analytes, in order to enhance the selectivity and specificity of the sensor device. The molecular probe we used was purified by an extremophile organism, Thermococcus litoralis: the protein is very stable in a wide range of temperatures even if with different behavior respect to the interaction with the ligand.

Research into the development of an Early Warning Harmful Algae Bloom (HAB) Sensing System for use in Underwater Monitoring Applications is presented. The sensor proposed by the authors utilises the complex ties between ocean colour, absorption and scattering, along with algae pigmentation. The objective is to develop a robust inexpensive sensor for use in an early warning system for the detection and possible identification of Harmful Algae Blooms. The sensing mechanism utilised in this system is based on a combination of absorption and reflection spectroscopy and Principle Component Analysis (PCA) signal processing. Spectroscopy is concerned with the production, measurement, and interpretation of electromagnetic spectra arising from either emission or absorption of radiant energy by various substances (or HABs in this application). Preliminary results are presented from the interrogation of chlorophyll, yeast and saline solutions, as well as levels of absorption obtained utilising two dyes Blue (brilliant Blue (E133) and Carmoisine (E122) mix) and Red (Ponceau (E124) and Sunset yellow (E110) mix).

Polymer photoelectronic device based on interaction between &pgr;-conjugated polymer matrices and photochromic molecules was fabricated. The theoretical and experimental studies proved that the photochromic reaction in studied devices should eventuate in changes of optical and electrical properties of polymers such as luminescence and conductivity. The quantum chemical calculations showed that the presence of dipolar species in the vicinity of a polymer chain modifies the on-chain site energies and consequently increases the width of the distribution of hopping transport states. Optical switching was studied using standard absorption and photoluminescence spectroscopy. A strong photoluminescence quenching after the photochromic conversion caused by radiative energy transfer was observed. The influence of photoswitchable charge carrier traps on charge transport was evaluated by current-voltage measurement and by Impedance spectroscopy method. It was shown that deep traps may significantly affect energy of the transport level, and thus control the transport of charge carriers. Based on these findings, polymer optical sensor was proposed.

The dispersion relations for TE polarized waves guided by thin dielectric film surrounded by a nonlinear cladding and a linear substrate are presented. The sensitivity of the effective refractive index on the cladding index in evanescent optical waveguide sensor is derived. Closed form analytical expressions and normalized charts are given to provide the conditions for the maximum sensitivity of nonlinear sensors when the measurand is homogeneously distributed in the semi-infinite waveguide cover (homogeneous sensing). The results will be compared with those of the well known linear evanescent wave sensors.

The resolution parameter of CCD is the factor which limits the spatial resolution of optoelectronic system. The using of high-resolution CCD is not always possible, especially for measurements in IR wavelength (1350nm) band. The purpose of given work is increasing the spatial resolution of the newly introduced Medianfield method which is focused on beam profile measurements for fiber-chip coupling systems by means of processing low-resolution images sequences. The results of numeric experiments show that the given image restoration method makes it possible the super-resolution restoration of images for possible transmission of information about high spatial frequencies, through diffraction limited optical system. Theoretical assessment allows to predict required conditions for this transmission. Results of experiments for super-resolution images which differ by sub-pixel shift show possibility of theoretical prediction optimal parameters for image (signal) restoration (required number of processed images, point spread function and etc.)

We have developed image intensifier tubes with delay-anode read-out for time- and position-sensitive photon counting. The timing precision is better than 1 ns with 1000x1000 pixels position resolution and up to one megacounts/s processing rate. Large format detectors of 40 and 75 mm active diameter with internal helical-wire delay-line anodes have been produced and specified. A different type of 40 and 25 mm tubes with semi-conducting screen for image charge read-out allow for an economic and robust tube design and for placing the read-out anodes outside the sealed housing. Two types of external delay-line anodes, i.e. pick-up electrodes for the image charge, have been tested. We present tests of the detector and anode performance. Due to the low background this technique is well suited for applications with very low light intensity and especially if a precise time tagging for each photon is required. As an example we present the application of scintillator read-out in time-of-flight (TOF) neutron radiography. Further applications so far are Fluorescence Life-time Microscopy (FLIM) and Astronomy.

A plastic optical fiber sensor that permits a simultaneous measure of liquid level and refractive index has been developed. The device has been realized with a fiber pair of two standard plastic optical fiber, which represent the probe of the proposed sensor. One of the fibers transmits the light towards the liquid under test through a lens. The reflected light is collected by the second fiber to a photodiode, whose output is amplified and sent to a processing electronic circuit. Different liquids have been considered for the measurements. A maximum distance of about 130 cm has been obtained. Moreover, for a fixed distance value, the highest output voltage has been reached with the liquid under test characterized by the highest refractive index value. In order to understand this behaviour, measurements have been performed by adding different quantities of sugar in the water, thus changing its refractive index.

Optical capillaries are used in capillary gas and liquid chromatography, capillary electrophoresis, absorbance spectroscopy, Raman spectroscopy etc. These micro-fluidic methods find applications in biotechnologies, medical diagnostic, drug discovery and environmental sciences. In the presented work we discuss some aspects of light guidance in capillary tubing made from silica glass or Teflon AF. The wide range of capillary constructions allows them to be used advantageously in specific applications. We have analyzed both theoretically and experimentally partially liquid filled optical capillaries as fiber optic sensor elements in laser light transmission and reflection conditions at 670, 1310 and 1550 nm. We have shown that the light transmission properties and signal in the reflectometric mode of work depend on capillary construction, their length and position of inserted liquid drop. The results obtained by us show that capillary tubing can be used as sensing elements in optical fiber sensors of surface tension and viscosity of small liquid samples with volume below 10^-8 cm³.

In this work, we report the experimental investigation of the sensitivity characteristics to the surrounding refractive index (SRI) in thinned long period gratings for a wide range of fiber diameters and different low orders cladding modes. Wet chemical etching combined with microscopic analysis allow us to identify the experimental dependence of the SRI sensitivity on the cladding radius.

A reflection-type side-polished optical fiber submersion sensor with an optical fiber mirror in a manhole is proposed. When this sensor is submerged into distilled water in a manhole and the measurement is made at about 1km from the sensor, the throughput power gain is changed by about 2.04dB at 1540nm and the resonance wavelength shifts from 1540nm to 1541.6nm.

In this paper, we proposed a chemical-gas fiber sensor based on the poly-aniline film coated on the surface of an etched fiber grating and experimentally demonstrated for detecting ammonia gas. This sensing mechanism is based on the testing gas to interact with the poly-aniline coating film on the surface of the fiber grating to cause the thin-film index change and then to create the Bragg wavelength shift or grating reflectivity variation. The sensitivity and response time of this sensor for measuring ammonia gas are around 0.73 nm per percent concentration and tens of mini-seconds respectively, which depend on the optical characteristics of fiber grating, the diameter of fiber cladding, and the constituents of chemical sensing film. This sensor may provide a simple, reliable, repeatable and non-destructive fiber sensing technique.

Ordinary perimeter security systems consist of many individual sensors with detection range 200-300 meters. These limitations are connected with physical phenomena that are used in microwave and infrared barriers as well as in ground and fence cable sensors. On the contrary, fiber optic perimeter sensors can be applied in the range of many kilometers and zone length 200-300 meters is degradation of their possibilities. This paper presents investigation results of a new generation of the fiber optic perimeter sensor in a two Sagnac and Sagna'c interferometers configuration. This system can detect a potential intruder and determine its position along a protected zone. We propose a method that makes use of the inherent properties of both interferometers. After demodulation of signals from both interferometers, obtained amplitude characteristic of the Sagnac interferometer depends on position of a disturbance along the both interferometer. So, quotient of both demodulated characteristics is proportional to the position of the disturbance. Arrangement of a laboratory model of the sensor and its signal processing scheme is presented. During research of a laboratory model, it was possible to detect the position of the disturbance with resolution of about 50m along a 10-km long sensor.

The optoelectronic observational system with active illumination is the innovatory method of images registration. The paper presents comparisons of passive and active images methods of registration. The realisation of framing space sector was graphically presented. The basic data were passed about worked out laboratory set up realizing images acquisition according to suggest active method. The results of conducted laboratory and ground tests were also presented. Received results shows on potentially large measuring and application possibilities methods of observation with active illumination; a) the spatial selection of observed scene elements, b) the registration and analysis high-speed processes c) the detection and identification of objects during observations in unfavourable lighting conditions and /or visibility. Authors of elaboration may hope, that devices basing on proposed method can become valuable measuring tool.

In the last decade a huge number of SnO₂-based gas sensors have been proposed for environmental monitoring, automotive applications, air conditioning in houses, airplane and aircrafts. However, most of the proposed sensors work at very high temperatures in order to reach high sensitivities. Here, a SnO₂-based optical fiber sensor is proposed for the room temperature detection of chemical pollutants in air. Particles layers composed by tin dioxide grains, with wavelength and subwavelength dimensions, resulted very promising because they are able to significantly modify the optical near field profile emerging from the film surface due to local enhancements of the evanescent wave contribute, and thus to improve the sensitivity to surface effects induced by the analyte interaction. The room temperature sensing performances of SnO₂-based particles layers towards environmental pollutants have been investigated by the exposure to different concentrations of toluene and xylene vapors as well as gaseous ammonia. They have also been compared with the performances obtained with other optical fiber sensors in the same configuration, but coated with different sensitive materials, such as Single-Walled carbon nanotubes. The preliminary results obtained evidenced the surprising capability of the SnO₂-based optical sensor to detect chemical pollutants at ppm level in air at room temperature. Finally, preliminary results on the effects of the processing parameters and post processing thermal annealing on film morphology and optical near field are presented.

An antimicrobial testing method using surface plasmon resonance to improve the present techniques is reported in this paper. Different from conventional methods, namely Kirby-Bauer disk diffusion and variations of broth microdilution, the examination time is reduced from 18-24 hours or more to less than one hour after the treatment of antibiotics. E-coli resistant and susceptible to ampicillin are used in the test to demonstrate this innovative method. It is generally known that discovering a method to exam the bacterium resistance rapidly and correctly is very important for patients and for preventing infective disease from spreading. The method reported can benefit this requirement.

FeNbB amorphous ribbons are promising soft magnetic materials with adjustable surface magnetic properties. Field-annealing is applied to control nano-crystallized surface magnetic films, which can be monitored by using magneto-optical techniques. In this paper we analyze depth sensitivity of magneto-optic methods and investigate the surface magnetic properties of amorphous ribbons. Magneto-optic response and depth sensitivity is modeled using 4 x 4 matrix formalism of light propagation in anisotropic multilayers. Optical and magneto-optical properties of near surface nano-crystallized phases differ from those of deeper bulk material. The complex longitudinal magneto-optic Kerr effect is measured for s- and p-polarized incident light. Both magneto-optical angles: the Kerr rotation and Kerr ellipticity are analyzed. Separation of magneto-optic contributions from different layers is obtained using different phase sensitive and penetration depth of the complex magneto-optic measurements. For these measurements we use magneto-optic vector magnetometry based on differential intensity between two polarization states.

Herein we present optical receivers with external large-area photodiode. It is intended as POF receiver for 1.25Gb/s optical fiber-line access networks. Further an overview on high-speed optical receivers with integrated and external detector in CMOS and BiCMOS, as well as in technologies of III-V compounds is provided. This work's receiver circuits are realized in 0.35μm SiGe BiCMOS technology. The first amplifier stage is a two-transistor transimpedance amplifier using a common-emitter and an emitter-follower configuration. The light-sensitive areas of the two receivers presented are 0.25mm² (squared PIN diode) and 0.5mm² (circular APD), with a rise time of 0.4ns and 0.7ns, respectively, at 850nm light. A high sensitivity is also required, where the receiver with external PIN diode reaches a sensitivity of -25.9dBm at the optical input using low-cost silicon-based material only.

We present the study of potential application of Cavity Enhanced Absorption Spectroscopy (CEAS) for construction of fully optoelectronic and portable NO₂ detector which could replace the commonly used chemical detectors. We demonstrate an experiment on detection of NO₂ in the ambient air. The concentration of investigated absorber was found by determination of decay time of pulse radiation trapped in the optical cavity constructed with two mirrors of a very high reflectivity coefficient (R > 99,99%). As a light source a blue pulsed diode laser was applied. The output signal was detected by a photomultiplier and analysed by a digital oscilloscope. For this construction the detection limit better than 1 ppb was obtained. The cavity parameters and it's adjustment were controlled by a beam from a red laser that is not absorbed by NO₂. In order to perform the measurements in two spectral regions the special mirrors have been developed. Study of influence of another NO_x compounds (especially NO₃) on final result was investigated as well.

In the present work the interaction between GST (glutathione-S-transferase) and immobilized glutathione on the mixed thiol monolayers was investigated by surface plasmon resonance method. The interfacial structures based on mixed monolayer of CH3-/C(O)OH and OH-/C(O)OH- terminated thiols as an support for the immobilization of glutathione (GSH)where used. The range of matrix/reactive groups ratio was up to 1:700. The standard procedure with activation by NHS/EDC with further applying of PDEA was used for GSH binding. It was demonstrated, that both the nature of the matrix terminal group and the density of the immobilized ligand are important for the efficiency of the protein-surface and protein-protein interaction at the sensor surface. Testing of the surface coupled GST by specific anti-GST antibodies shown the same character of the sensor response versus GSH density.

A novel soluble phthalocyanine compound, i.e zinc phthalocyanine (sulfonamide) has been synthesized by chemical substitution of zinc phthalocyanine and used to produce thin solid films by means of the spin coating technique. The chemical structure of the spin coated films has been investigated by FT-IR analysis. Atomic Force Microscopy (AFM) has been used to characterize the film morphology and to measure the film thickness. The spin coated films have been tested as optical sensing materials of volatile organic compounds such as methanol, ethanol and 2-propanol. The change of optical reflectance of the films upon exposure to alcohol-vapour-containing atmospheres has been measured versus alcohol concentration and exposure time. The films exhibit a fast and reproducible response, with a complete and fast recovery in methanol and ethanol-containing atmospheres, while diffusion-driven effects appear during exposure to 2-propanol. The response and sensitivity of the films to ethanol vapour is higher than to methanol and 2-propanol.

Quasi single mode fiber is a fiber supporting a few modes only. If the operational wavelength of the light source will be shorter than the cut-off wavelength is, then the fiber will support except fundamental mode LP₀₁ several higher modes too. Such fiber conserve themselves the advantageous characteristics for telecommunication application (small attenuation, slight dispersion), but it is possible to use them for sensor-based applications utilizing the mode coupling among several guided modes. This paper describes design of optical fiber working as a conventional telecommunication fiber at wavelength of 1550 nm and temperature sensing fiber at the wavelength of 850 nm or 675nm. In the paper the basic theory together with the simulation of the mode distribution will be shown temperature changes within the interval 20°C-100°C and real mode patterns of such fiber.

In this paper we report results for an intrinsic evanescent field sensor based on not-regular plastic optical fiber with polymer film containing Malachite Green MG⁺([PhC(C₆H₄NMe₂)₃]⁺) as an absorption reagent, which coats the fiber's imperfected area. A theoretical model was developed which shows that changes of light in such structure result from the attenuation of light in the strait and bent imperfected fiber. In this model, the imperfected area with malachite green polymer film is replaced by a uniform layer with a complex refractive index. The changes in color and absorption characteristics of the polymer film depend on the acidic and basic environmental properties in the sensing area. Additional increase of the evanescent field interaction can be achieved by decrease the bending radius of the fiber with the coated imperfection area at the middle of the bent fiber. An imperfected plastic optical fiber with Malachite Green coating has been presented for the detection of ammonia vapor. The initial results show that depending on the sensing application demands, it is possible to design a high sensitive sensor with a relatively long response time, while when the demands require fast response times the sensor with less sensitivity can be used. In addition, the sensors' sensitivity can be calibrated in real-time by changing the bending radius.

We studied both experimentally and numerically the spectral behavior of modal birefringence in channel waveguides inscribed in PMMA by DUV illumination. The measurements of birefringence were carried out using spectral interference method for different waveguide widths, respectively 2, 3, 4, 5, 6 μm which were inscribed using 3 J/cm². We have also modeled the spectral dependence of birefringence related only to waveguide geometry using FEM method. High discrepancy reaching one order of magnitude was observed between measured and calculated birefringence. This is related to the fact that numerical analysis accounts only for so called geometrical birefringence induced by the asymmetry of the waveguide, while in measurements the overall modal birefringence relates to both the geometrical and the material effect. Our measurement results indicate that the contribution of the material birefringence in the analyzed waveguides may reach up to 3×10^-4 in a short wavelength range.

We report a surface plasmon resonance (SPR) sensor based on two-plasmon-spectroscopy on a special bi-diffractive grating and investigate its ability to distinguish contributions to sensor response due to surface refractive index changes (i.e. binding) and due to refractive index changes in the whole sample. Theoretical analysis yielding an estimate of an error of such decomposition is presented and used to compare performance of this sensor to that of an alternative approach based on simultaneous excitation of short-range and long-range surface plasmons on a thin metallic layer.

The performance of infrared InAs homojunction and heterojunction photodiodes (PD) and possibilities of its improvement are analyzed both theoretically and experimentally. The figures of merit such as the resistance-area product R₀A, the carrier lifetime and the quantum efficiency are studied. The excess carrier lifetime in InAs are calculated for radiative and Auger recombination mechanisms using three- and four-band Kane model. Theoretical limit of threshold parameters in InAs-based photodiodes is calculated for intrinsic (radiative and Auger) recombination processes. The diffused PD were prepared by short-term cadmium diffusion into substrates with n-type conductivity. In the investigated PD the total dark current is determined by the diffusion carrier transport mechanism at room temperature. Experimentally proved that heterojunction PD p⁺-InAsSbP/n-InAs can be more effective as sensitive element in gas sensors operated at room temperature in comparison with commercially available PD. Experimentally proved that heterojunction PD p+-InAsSbP/n-InAs can be more effective as sensitive element in gas sensors operated at room temperature in comparison with commercially available PD. Their threshold parameters (current sensitivity and detectivity) have approximately the same values as in commercially available photodiodes, but they have higher values of the resistance-area product.

We report a SPR biosensor based on long-range (LR) and short-range (SR) surface plasmon (SP) modes excited simultaneously on a diffraction grating. Employing the LRSP and SRSP in the grating-coupled SPR sensor offers several interesting features such as extended probe depth of the LRSP and ability to distinguish sensor response caused by bulk and surface refractive index changes. Prototype device based on wavelength interrogation of SPs was developed and be tested in model refractometric experiment. This paper presents results of theoretical analysis and experimental characterization of the sensor. Sensitivity of the laboratory prototype of the sensor agrees well with the theory. The sensor is shown to be able to detect changes in the refractive index as small as 3.5 x 10^-6 RIU (refractive index unit).

Propagation characteristics of an annular beam through random media (high-concentrated scattering media) were examined for detail. In nature, the light propagation in random media is classified broadly into two categories; exponential attenuation by the directly delivered light and moderate attenuation by the scattering light. The authors found that the annular beam had discriminative propagation related to the waveform transformation into the non-diffractive beam by self-focusing of an annular beam between the above two categories. In this study, central core beam and its behavior, which appeared on optical axis when the annular beam propagated in the random media of a certain concentration, were investigated.

This paper details a method for measuring the MTF for optoelectronic detector. A description of a test facility for testing and evaluating MTF is given. We use a knife-edge target to measure MTF. The Pentium III computer system takes the charge of controlling and calculating.

Light-emitting diodes (LEDs) and spectral-matched photodiodes (PDs) based on GaInAsSb/AlGaAsSb and InAs/InAsSbP heterostructures grown by LPE and MOVPE for the spectral range 1.6-4.8 μm are presented. New aproach have been proposed to increase quantum efficiency and optical power of the LEDs. Optical sensors based on the LEDs and PDs are considered for detection of methane, carbon dioxide and some anaesthetics for medicine.

In this work, we report on the integration of Hollow-core Optical Fibers (HOF) and Single Walled Carbon NanoTubes (SWCNTs) in order to obtain new functionalized devices by means of the modification of the photonic bandgap (PBG) characterizing the HOF itself. The samples were obtained by coating and partially filling by SWCNTs the termination of HOFs. The infiltration of SWCNTs inside the HOF holes has been accomplished by means of the Langmuir-Blodgett technique. Far field transmission characterizations have been carried out at 1550nm in order to study the influence of the carbon nanotubes within the HOF holes on the HOF PBG. Finally, in light of the sensing features of the SWCNTs, the realized samples have been employed as opto-chemical sensors for volatile organic compounds (VOCs) detection and their sensing capability has been proved by their exposure to VOCs traces. Experimental results demonstrate the success of the SWCNTs partial filling within the HOF holes, the influence of the deposition parameters on the HOF PBG and sensing performances as well as the sensor capability to perform VOCs detection with a good sensitivity and fast response times.

The RF-sputtered ITO layers were used as the transparency contact layer of the MSM PDs. The plasma gas would alter the optical transmittance and the schottky barrier height between the ITO layer and InGaAsN absorption layer. Three kinds of plasma gases were studied including Ar, Ar/N₂, and Ar/O₂. The Schottky barrier heights were 0.510 eV, 0.572 eV, and 0.574 eV when using Ar, (Ar/N₂), and (Ar/O₂) as the plasma gas; besides, the optical transmittances were 92.56%, 93.12% and 96%, respectively. Although the ITO film sputtered in the Ar/O₂ ambient has highest transmittance and Schottky barrier height, the high resistivity limited the photocurrent of the photodetectors; it is almost three orders lower than the others. Consequently, using the Ar/N₂ as the plasma gas would be a suitable choice regarding the MSM photodetector application. The highest contrast ratio between photo-current and dark-current of the InGaAsN MSM photodetectors were 5, 25 and 12 (measured under 0.2V) using Ar, Ar/N₂, and Ar/O₂ as the plasma gases.

The trade-off between resolution and dynamic range must be managed in the design of a Shack-Hartmann wavefront sensor (SHWS). A relatively large f-number of the microlenses should be chosen to get good lateral and vertical resolutions, but the corresponding dynamic range of measurement is degraded. To extend the dynamic range while keeping a good resolution, we propose a novel SHWS based on a cylindrical microlens array. Instead of the conventional spot pattern, two orthogonal line patterns with the microcylinders oriented in the horizontal and vertical directions are detected on a conventional CCD array. Because the sampled data are now connected along continuous lines, a self-developed line-tracking algorithm unequivocally localizes them even if they are highly distorted. With the sensor constructed, a wavefront transmitted by a commercial progressive addition lens with more than 80&lgr; peak-to-valley height has been succesfully measured. The vertical resolution of the sensor was also calculated, resulting of &lgr;/25 at the wavelength used (&lgr;=635 nm).

The usefulness of the visualisation and animation of polarisation influence on the fibre-optic sensors in the Sagnac configuration is presented. The Jones' matrix calculus and the coherence matrix approach have been used for the fibre-optic elements and all interferometric systems description, respectively. Such uniform description gives a possibility to obtain analytical relations, which depend on fundamental system parameters. Because the final relations are usually too complicated for physical interpretation, the possibility of simulation of system work by application of the animated graphics is main subject of this paper.

The basic optical set-up for demodulation of phase signal propagating in singlemode fiber - optics was described in this article. In this arrangement two fiber - optics (modulated signal in first and reference in second) was used. Both fibers in the final part of this set-up are parallel to each other at distance between them equals "d". After propagation by fiber beam goes through the lens. The spatial distribution of light amplitude in the focal plane of the lens is proportional to the Fourier transform on the output light in fibers and modulated with frequency proportional to "1/d". The power spectral density of the spatial distribution of light by bicell photodetector was analyzed. The sum and difference of output signals from channels on the detector is depending on the power spectral density, bicell gap and cosine and sine of phase respectively. On the ground of this results it is possible to identify demodulate of different types of modulation without any a priori information.

Italian extra virgin olive oils bearing labels of certified area of origin were considered. Their multispectral digital signature was measured by means of absorption spectroscopy in the 200-1700 nm spectral range. The instrumentation was a fiber optic-based, cheap, and compact device. The spectral data were processed by means of multivariate analysis and plotted on a 2D classification map. The map showed sharp clusters according to the geographical origin of the oils, thus demonstrating the potentials of UV-VIS-NIR spectroscopy for optical fingerprinting. Then, the spectral data were correlated to the content of the most important fatty acids. The good fitting achieved demonstrated that the optical fingerprinting can be used also for predicting nutritional and chemical parameters.

The presence of thin cover layer on planar waveguide influences its propagation characteristics. A generalized m-line spectroscopy method enables the evaluation of the parameters (the refractive index, n and the thickness, t) of the subguiding layers deposited on a planar waveguide. In this paper algorithm for determination of the parameters of the thin layer (deposited on waveguide with previously evaluated index profile by m-line method) has been presented.

We show how a Fabry Perot interferometer could be used to determine the gravitational axis of the earth g with an high sensitivity. Our method lie g axis to an optical beat frequency value between two lasers. The principle is described and a budget error is presented. The sensitivity of the sensor is estimated to be below of 85 nrad/MHz. This method could be used as a high sensitivity and absolute tilt sensor or even as a seismometer. This sensor is dedicated to the french watt balance project as described in this paper.