This PDF file contains the front matter associated with SPIE Proceedings Volume 9506, including the Title Page, Copyright information, Table of Contents, Authors, Introduction (if any), and Conference Committee listing.

This contribution describes the modeling of CMOS image sensors employed in time-of-flight (ToF) sensor systems for 3D ranging applications. Our model relies on the theoretical description of photo-generation, charge transfer including diffusion, fringing field, and self-induced drift (SID). This method makes it possible to calculate the time-dependent charge carrier generation, transfer, and distribution. The employed approach allows elimination not only of irradiance-dependent charge transfer, but also of undesired reflectance effects, and the influence of ambient light through an in-pixel background measurement. Since the sensor is operated with very short integration times it is crucial to accomplish a fast transfer of the generated charge from the photodetector to the sense node, and speedy conversion into an electrical signal at its output. In our case, we employed a lateral drift field photodetector (LDPD), which is basically a pinned photodiode with a built-in drift field formed by a doping gradient. A novel pixel structure is presented which is optimized for a fast charge transfer by the appliance of the shown model. Numerical calculations predict a two times faster charge collection.

Digital cameras are subject to physical, electronic and optic effects that result in errors and noise in the image. These effects include for example a temperature dependent dark current, read noise, optical vignetting or different sensitivities of individual pixels. The task of a radiometric calibration is to reduce these errors in the image and thus improve the quality of the overall application. In this work we present an algorithm for radiometric calibration based on Gaussian processes. Gaussian processes are a regression method widely used in machine learning that is particularly useful in our context. Then Gaussian process regression is used to learn a temperature and exposure time dependent mapping from observed gray-scale values to true light intensities for each pixel. Regression models based on the characteristics of single pixels suffer from excessively high runtime and thus are unsuitable for many practical applications. In contrast, a single regression model for an entire image with high spatial resolution leads to a low quality radiometric calibration, which also limits its practical use. The proposed algorithm is predicated on a partitioning of the pixels such that each pixel partition can be represented by one single regression model without quality loss. Partitioning is done by extracting features from the characteristic of each pixel and using them for lexicographic sorting. Splitting the sorted data into partitions with equal size yields the final partitions, each of which is represented by the partition centers. An individual Gaussian process regression and model selection is done for each partition. Calibration is performed by interpolating the gray-scale value of each pixel with the regression model of the respective partition. The experimental comparison of the proposed approach to classical flat field calibration shows a consistently higher reconstruction quality for the same overall number of calibration frames.

A light field camera acquires the intensity and direction of rays from a scene providing a 4D representation L(x,y,u,v) called the light field. The acquired light field allows to virtually change view point and selectively re-focus regions algorithmically, an important feature for many applications in imaging and microscopy. The combination with hyperspectral imaging provides the additional advantage that small objects (beads, cells, nuclei) can be categorised using their spectroscopic signatures. Using an inverse fluorescence microscope, a LCTF tuneable filter and a light field setup as a test-bed, fluorescence-marked beads have been imaged and reconstructed into a 4D hyper-spectral image cube L_HSI(x,y,z,λ). The results demonstrate the advantages of the approach for fluorescence microscopy providing extended depth of focus (DoF) and the fidelity of hyper-spectral imaging.

Phase-sensitive optical time-domain reectometry (Φ-OTDR) seems to be the most appropriate solution for acoustic vibration along standard optical fiber detection. In general the sensing system measures phase changes of the received Rayleigh back-scattered signal in the fiber. Since the back-scattered signal intensity is decreased about tens of decibels in comparison to the forward propagating pulse power level, the received signal power level is very low. That is why the main limiting parameter of the system is the power level of the back-scattered signal, which limits maximum achievable distance. For long reach sensing it is necessary to create high power optical pulses with short time-duration. Direct pulse amplification by erbium doped fiber amplifier (EDFA) is an issue because of the pulses low repetition rate. We have designed and verified a simple method using a holding beam for amplifying of pulses with low repetition rate by standard telecommunication EDFA booster instead of deployment of an expensive optical shutter. A second CW laser with a different wavelength for EDFA stabilization is used in our setup. Because a pulse losses its energy during propagation in the fiber and with longer distances by 1^st order Raman amplifier (RA). In telecommunications this amplifier is used to compensate for fiber losses. The second setup uses remote amplification by remotely pumped erbium doped fiber (EDF) placed after a few tens of kilometers of sensing fiber. A pump laser is placed in the transmitter part of the system from where EDF is pumped. In this paper, we present an overview of few techniques for Φ-ODTR signals amplification and their verification by measurement.

Most embedded image processing SoCs available on the market are highly optimized for typical consumer applications like video encoding/decoding, motion estimation or several image enhancement processes as used in DSLR or digital video cameras. For non-consumer applications, on the other hand, optimized embedded hardware is rarely available, so often PC based image processing systems are used. We show how a real time capable image processing system for a non-consumer application - namely polarization image data processing - can be efficiently implemented on an FPGA and multi-core DSP based embedded hardware platform.

In micro-analytical chemistry and biology applications, optofluidic technology holds great promise for creating efficient lab-on-chip systems where higher levels of integration of different stages on the same platform is constantly addressed. Therefore, in this work the possibility of integrating opto-microfluidic functionalities in lithium niobate (LiNbO₃) crystals is presented. In particular, a T-junction droplet generator is directly engraved in a LiNbO₃ substrate by means of laser ablation process and optical waveguides are realized in the same material by exploiting the Titanium in-diffusion approach. The coupling of these two stages as well as the realization of holographic gratings in the same substrate will allow creating new compact optical sensor prototypes, where the optical properties of the droplets constituents can be monitored.

This paper is to review the research activities at City University London in the development of a range of fibre Bragg grating (FBG)-based sensors, including strain, temperature, relative humidity, vibration and acoustic sensors, with an aim to meet the increasing demands from industry for structural condition monitoring. As a result, arrays of optical fibre sensors have been instrumented into various types of structures, including concrete, limestone, marine propellers, pantograph and electrical motors, allowing for both static and dynamic monitoring and thus enhanced structural reliability and integrity.

The research of the luminescent properties of the inorganic glasses doped with copper molecular clusters that can be used as a sensitive medium of the temperature sensors is presented. The luminescent spectra of the borate and phosphate glasses in the temperature range 77-623 K are examined. The big luminescent thermochromism for borate glasses is observed: from 293K to 623K the luminescent band shift is found out to be 110nm.

A novel sensor for high-temperature measurement using Fiber Bragg grating (FBG) along with its low-cost interrogation system has been designed and tested. The sensor works based on measurement of the shift in Bragg wavelength that corresponds to the temperature induced strain by making use of a mechanical transducer. The transducing element provides temperature dependent strain on FBG by means of differential linear thermal expansion of two different materials, stainless steel and mild steel. The shift in Bragg wavelength of FBG due to this temperature induced strain is measured by using optical spectrum analyser (OSA). Further the bulk and expensive OSA is replaced by a low cost interrogation system that employed an LPG, a photodiode, a transimpedance amplifier, and a digital multimeter. The LPG converts wavelength information of FBG into its equivalent intensity modulated signal which is captured by a simple photodiode and then converted into voltage signal using the transimpedance amplifier. The designed sensor measures the temperature from 20°C to 1000°C with a resolution of 2°C.

In order to measure strain independently from temperature, hybrid solution based on a polarimetric and chirped Fiber Bragg Grating (FBG) sensors is proposed. The sensor is designed in a reflective configuration, where the chirped FBG is written on a highly birefringent (HB) fiber. The FBG act as a sensing element and also as a mirror for the polarimetric sensor. Information from both polarimetric and FBG part of the sensor can be determined independently from spectral analysis of the reflected light. Strain and temperature sensitivity of the proposed sensor solution is measured. Relation between both sensitivities are different for the FBG and the polarimetric sensor. Taking advantage of this, both temperature and strain can be determined by using only one sensing fiber.

A monolithic passively mode-locked laser is proposed as a compact optical sensor for displacements and vibrations of a reflecting object. The sensing principle relies on the change of the laser repetition frequency that is induced by optical feedback from the object under measurement. It has been previously observed that, when a semiconductor passively mode locked laser receives a sufficient level of optical feedback from an external reflecting surface it exhibits a repetition frequency that is no more determined by the mode-locking rule of the free-running operation but is imposed by the length of the external cavity. Therefore measurement of the resulting laser repetition frequency under self-injection permits the accurate and straightforward determination of the relative position of the reflecting object. The system has an inherent wireless capability since the repetition rate of the laser can be wirelessly detected by means of a simple antenna which captures the microwave signal generated by the saturable absorber and is emitted through the wiring of the laser. The sensor setup is very simple as it requires few optical components besides the laser itself. Furthermore, the deduction of the relative position of the reflecting object is straightforward and does not require any processing of the detected signal. The proposed sensor has a theoretical sub-wavelength resolution and its performance depends on the RF linewidth of the laser and the resolution of the repetition frequency measurement. Other physical parameters that induce phase changes of the external cavity could also be quantified.

The possibility of using semiconductor laser interferometers to measure displacements at the nanometer scale was demonstrated. The creation principles of miniature digital Michelson interferometers based on semiconductor lasers were proposed. The advanced processing algorithm for the interferometer quadrature signals was designed. It enabled to reduce restrictions on speed of measured movements. A miniature semiconductor digital Michelson interferometer was developed. Designing of the precision temperature stability system for miniature low-cost semiconductor laser with 0.01ºС accuracy enabled to use it for creation of compact interferometer rather than a helium-neon one. Proper firmware and software was designed for the interferometer signals real-time processing and conversion in to respective shifts. In the result the relative displacement between 0-500 mm was measured with a resolution of better than 1 nm. Advantages and disadvantages of practical use of the compact semiconductor digital interferometer in seismometers for the measurement of shifts were shown.

Rainfall measurement is performed on regular basis to facilitate effectively the weather stations and local inhabitants. Different types of rain gauges are available with different measuring principle for rainfall measurement. In this research work, a novel optical rain sensor is designed, which precisely calculate the rainfall level according to rainfall intensity. This proposed optical rain sensor model introduced in this paper, which is basically designed for remote sensing of rainfall and it designated as R-ORMS (Remote Optical Rainfall Measurement sensor). This sensor is combination of some improved method of tipping bucket rain gauge and most of the optical hydreon rain sensor’s principle. This optical sensor can detect the starting time and ending time of rain, rain intensity and rainfall level. An infrared beam from Light Emitting Diode (LED) through powerful convex lens can accurately determines the diameter of each rain drops by total internal reflection principle. Calculations of these accumulative results determine the rain intensity and rainfall level. Accurate rainfall level is determined by internal optical LED based sensor which is embedded in bucket wall. This internal sensor is also following the total internal reflection (TIR) principle and the Fresnel’s law. This is an entirely novel design of optical sensing principle based rain sensor and also suitable for remote sensing rainfall level. The performance of this proposed sensor has been comprehensively compared with other sensors with similar attributes and it showed better and sustainable result. Future related works have been proposed at the end of this paper, to provide improved and enhanced performance of proposed novel rain sensor.

Today, document counterfeiting is a global menace because of the advanced technologies available at ever decreasing prices. Instead of eschew the paper documents; applying efficient cost effective security methodologies are the feasible solutions. This paper reports a novel cost effective and simple optical technique using micro text encrypted optical variable device (OVD) threads, ultra-violet (UV) based optical invariable device (OID) patterns and artistic fonts for secure preparation of the documents and its forensic application. Applying any one of the above technique or together can effectively enhance the level of security of the most valuable document. The genuineness of the documents can be verified using simple decryption techniques.

Among all transduction methodologies reported in the field of solid state optical chemical sensors, the attention has been focused onto the optical sensing characterization by using propagating and localized surface plasmon resonance (SPR) techniques. The research in this field is always oriented in the improvement of the sensing features in terms of sensitivity and limits of detection. To this purpose different strategies have been proposed to realize advanced materials for high sensitive plasmonic devices. In this work nanostructured silica nanowires decorated by gold nanoparticles and active magneto-plasmonic transductors are considered as new biosensing transductors useful to increase the performance of sensitive devices.

Plasmonic amplification of fluorescence signal in bioassays with microarray detection format is reported. A crossed relief diffraction grating was designed to couple an excitation laser beam to surface plasmons at the wavelength overlapping with the absorption and emission bands of fluorophore Dy647 that was used as a label. The surface of periodically corrugated sensor chip was coated with surface plasmon-supporting gold layer and a thin SU8 polymer film carrying epoxy groups. These groups were employed for the covalent immobilization of capture antibodies at arrays of spots. The plasmonic amplification of fluorescence signal on the developed microarray chip was tested by using interleukin 8 sandwich immunoassay. The readout was performed ex situ after drying the chip by using a commercial scanner with high numerical aperture collecting lens. Obtained results reveal the enhancement of fluorescence signal by a factor of 5 when compared to a regular glass chip.

We investigate selected periodic arrays of nanostructures inspired by metasurfaces originally used in metamaterial structures and evaluate their potential for surface plasmon resonance applicable in sensing. Building blocks including rectangles, cut wires, crosses, fishnets, split ring resonators were ordered on suitable substrates and their reflection (R), transmission (T), and loss energy (L) spectra were calculated. The numerical studies were performed using our efficient in-house two-dimensional rigorous coupled-wave analysis technique. Our technique incorporates all the key improvements of the method available, taking into account both proper Fourier factorization rules, adaptive spatial resolution techniques, as well as structural symmetries. Using the R, T, and L spectra, we investigated spectral sensitivity of SPR and calculated the respective SPR sensor characteristics, such as figures of merit (FOM), enabling direct comparison of various structural morphologies for potential sensing applications. Also, optimization of the structures in terms of FOM has been performed to identify the most promising candidates. Additionally, to allow for interpretation of spectral resonant features and the interplay of individual and surface lattice resonances, we were gradually changing the morphology of individual building blocks from one type of element to another one. We believe that this study will bring insight into plasmonic behavior of nanostructured metasurfaces and will further benefit research into SPR biosensors.

Surface plasmon resonance (SPR) is one of the recent applied technologies in bio-medical detection, and it is gradually accepted by the researchers. However, it is still not adopted widely and needs more efforts to improve. In our research work, a previous developed phase interrogation SPR detection system is modified and the concept of multi-incident angles of detecting light is used for obtaining more data. Besides, using the focusing characteristic of a cylindrical elliptic reflective mirror to have more than one measuring areas, and this can provide a control reaction accompanied with the experimental reaction on the chip at the same time. The phase variation of the sample variation with different detecting incident angle can provide more data and can reduce the errors, increase the resolution, and raise the detection ability. To acquire the inference fringes images of the phase, the time-stepped quadrature phase shifting method has been introduced, which required fewer images to retrieve the phase than the five-stepped phase shifting method. The data processing time can be reduced and our system would have the potential to measure the reaction in real-time. Finally, sodium chloride-water solution and Ethanol-water solution in different concentration has been measured to verify our system is workable.

We demonstrate a refractive index (RI) detection technique based on an array of nanometer scale slot-antennas milled in a thin gold layer using a single lithographic step. Our experimental Figures of merit (FOMs) of 140-210 in the telecom wavelength range approach the fundamental limit for standard propagating SPR sensors (~250). The underlying mechanism enabling such high FOMs is the combination of a narrowband resonance of the slot-antennas with degeneracy breaking of Wood’s anomaly under slightly non-perpendicular illumination. In addition, we study the sensitivity of the thickness of the analyte layer. This concept can be easily tuned to any desired wavelength and RI range by modifying the slot dimensions and the array spacing, thus rendering it highly attractive for numerous sensing applications.

Surface plasmon resonance (SPR) is a rapid and sensitive technique used for probing the biomolecular interactions in real time. Several new approaches have been suggested to improve the sensitivity of SPR sensors over the last two decades. Most of them are based on creating or patterning nanostructures/nanomaterials in order to enhance the sensitivity. Graphene offers several advantages due to its special optical and structural properties. Herein, we propose a new angular interrogated dual wavelength based differential detection approach for graphene based SPR sensing to increase the sensitivity. Reflectivity of the p-polarized incident light has been calculated using the N-layer model for the most common Kretschmann configuration. Sensitivity of the SPR with and without graphene layers has been calculated for single and dual wavelength based approaches. Computational results show that the proposed graphene SPR sensor has (1 + 0.4 L) η times higher sensitivity than the conventional gold thin film based SPR sensors. Further, increasing the number of graphene layers, L, improves the sensitivity. Where, η represents the enhanced sensitivity due to increased binding/adsorption of biomolecules on graphene over a gold thin film. Sensitivity analysis has been carried out for a refractive index (Δn) = 0.005 with L = 1 to 10.

Bloch surface waves (BSW) propagating at the boundary of truncated photonic crystals (1D-PC) have emerged as an attractive approach for label-free sensing in plasmon-like sensor configurations. Due to the very low losses in such dielectric thin film stacks, BSW feature very low angular resonance widths compared to the surface plasmon resonance (SPR) case. Besides label-free operation, the large field enhancement and the absence of quenching allow utilizing BSW coupled fluorescence detection to additionally sense the presence of fluorescent labels. This approach can be adapted to the case of angularly resolved resonance detection, thus giving rise to a combined label-free / labelled biosensor platform. It features a parallel analysis of multiple spots arranged as a one-dimensional array inside a microfluidic channel of a disposable chip. Application of such a combined biosensing approach to the detection of the Angiopoietin-2 cancer biomarker in buffer solutions is reported.

Gelatin is a biopolymer derived from collagen that is widely used in food and pharmaceutical products. Due to some religion restrictions and health issues regarding the gelatin consumption which is extracted from certain species, it is necessary to establish a robust, reliable, sensitive and simple quantitative method to detect gelatin from different parent collagen species. To the best of our knowledge, there has not been a gelatin differentiation method based on optical sensor that could detect gelatin from different species quantitatively. Surface plasmon resonance (SPR) based biosensor is known to be a sensitive, simple and label free optical method for detecting biomaterials that is able to do quantitative detection. Therefore, we have utilized SPR-based biosensor to detect the differentiation between bovine and porcine gelatin in various concentration, from 0% to 10% (w/w). Here, we report the ability of SPR-based biosensor to detect difference between both gelatins, its sensitivity toward the gelatin concentration change, its reliability and limit of detection (LOD) and limit of quantification (LOQ) of the sensor. The sensor’s LOD and LOQ towards bovine gelatin concentration are 0.38% and 1.26% (w/w), while towards porcine gelatin concentration are 0.66% and 2.20% (w/w), respectively. The results show that SPR-based biosensor is a promising tool for detecting gelatin from different raw materials quantitatively.

Currently, a combination of technologies is typically required to identify and classify leukemia cells. These methods often lack the specificity and sensitivity necessary for early and accurate diagnosis. Here, we demonstrate the use of Raman spectroscopy to identify normal B cells, collected from healthy patients, and three ALL cell lines (RS4;11, REH and MN60 at different differentiation level, respectively). Raman markers associated with DNA and protein vibrational modes have been identified that exhibit excellent discriminating power for leukemia cell identification. Principal Component Analysis was finally used to confirm the significance of these markers for identify leukemia cells and classifying the data. The obtained results indicate a sorting accuracy of 96% between the three leukemia cell lines.

Surgery on tumours commonly involves a lumpectomy method, where a section of tissue containing the tumour is removed, to improve cosmetic outcomes and quality of life. Following surgery, the margins of the removed section are checked by pathology tests to ensure that the entire tumour has been removed. Unfortunately, approximately 15-20% of margins show incomplete removal and require a subsequent operation to remove the remaining tumour. Tumour detection during surgery could allow the removed section to be enlarged appropriately, reducing the likelihood of requiring subsequent surgery. A change in the extracellular pH in the vicinity of a tumour, when compared to normal tissue, has been shown previously in literature. We have fabricated an optical fibre tip pH sensor by embedding a fluorophore within a photopolymerised acrylamide polymer on the tip of a 200 micron diameter silica fibre. Preliminary measurements of human melanoma samples have shown a significant difference in the measured pH values between tumour and normal tissue. This demonstration paves to way to highly accurate margin detection during surgery.

Acidity of an environment expressed as pH is one of the key biological parameters. An optical sensing scheme together with the use of optical fiber probes can bring advantages to the pH monitoring such as fine spatial resolution, less interference with biological material or immunity to the electromagnetic field. An optical pH-sensor with fine spatial resolution suitable for measurement of pH in near-neutral range is presented and the influence of sensing probe preparation process onto the sensor performance is discussed in the paper. The sensor is based on an ion pair of 8- hydroxypyrrene-1,3,6-pyrene trisulfonic acid trisodium salt (HPTS) and hexadecyltrimethylammonium bromide (CTAB) immobilized by a sol-gel method on the tip of tapered-fiber probes. It was found that the sensor performance is affected significantly by the shape of the sensing layer.

So as to covalently graft a chemical on a substrate, the GraftFast^TM process can be used; the only requirement is that the chemical has at least one aromatic primary amine. In this work, this simple and fast process is presently used to graft dyes that are pH sensitive on an optical fiber, thus creating a pH sensor called optode. The major asset of this grafting process is that the dye is covalently grafted on the fiber, resolving stability issues encountered with other techniques – like physical entrapment or electrostatic interactions. Two different dyes have been successfully grafted on gold lamellas (which are the reference substrates for the GraftFast^TM process), and an innovative experimental method to increase the thickness of the dye layer has been developed.

The production of reactive oxygen species (ROS) is known to affect the developmental competence of embryos. Hydrogen peroxide (H₂O₂) an important reactive oxygen species, is also known to causes DNA damage and defective sperm function. Current techniques require incubating a developing embryo with an organic fluorophore which is potentially hazardous for the embryo. What we need is a localised ROS sensor which does not require fluorophores in solution and hence will allow continuous monitoring of H₂O₂ production without adversely affect the development of the embryo. Here we report studies on such a fibre-based sensor for the detection of H₂O₂ that uses a surface-bound aryl boronate fluorophore carboxyperoxyfluor-1(CPF1). Optical fibres present a unique platform due to desirable characteristics as dip sensors in biological solutions. Attempts to functionalise the fibre tips using polyelectrolyte layers and (3-aminopropyl)triethoxysilane (APTES) coatings resulted in a limited signal and poor fluorescent response to H₂O₂ due to a low tip surface density of the fluorophore. To increase the surface density, CPF1 was integrated into a polymer matrix formed on the fibre tip by a UV-catalysed polymerisation process of acrylamide onto a methacrylate silane layer. The polyacrylamide containing CPF1 gave a much higher surface density than previous surface attachment methods and the sensor was found to effectively detect H₂O₂. Using this method, biologically relevant concentrations of H₂O₂ were detected, enabling remote sensing studies into ROS releases from embryos throughout early development.

To unravel cell complexity, living-cell chips have been developed that allow delivery of experimental stimuli but also measurement of the resulting cellular responses. We have been developing a new concept for multiplexed detection of biomolecules secreted by different cancer cells. In the present report, we are making the proof of concept of cell small populations (from 1 to 100 cells) spotting, culture and secretion detection on a gold surface. For that purpose, antibodies and different cell lines were spotted using a piezoelectric spotter. In order to keep the cells in a hydrated environment during the robotized micropipetting and to address different cell lines on a single chip, a biocompatible alginate polymer was used. This approach enables the encapsulation of the cell in a very small volume (30 nL), directly on the substrate and permits a precise control of the number of cells in each alginate bead. After 24h of culture, the adherent cells are ready for surface plasmon resonance imaging (SPRi) experimentation. To enable the detection of secreted proteins, various antibodies are immobilized in an organized manner on a SPRi sensor and permitted the multiplex detection of different proteins secreted by the different cultured cell lines. Evidence of the real-time detection will be presented for Prostate Specific Antigen (PSA) and β-2-microglobulin (B2M) secreted by prostate cancer cells following induction by dihydrotestosterone (DHT). Different kinetics for the two secreted proteins were then demonstrated and precisely determined using the chip. There is no doubt that our chip will, in a near future, be applied to more multiplexed and complex biological secretion systems for which kinetic data are at the moment not reachable using standard cellular biology tools.

Recently, optical micro-bubble resonators (OMBRs) have gained an increasing interest in many fields of photonics thanks to their particular properties. These hollow microstructures can be suitable for the realization of label – free optical biosensors by combining the whispering gallery mode (WGM) resonator properties with the intrinsic capability of integrated microfluidics. In fact, the WGMs are morphology-dependent modes: any change on the OMBR inner surface (due to chemical and/or biochemical binding) causes a shift of the resonance position and reduces the Q factor value of the cavity. By measuring this shift, it is possible to obtain information on the concentration of the analyte to be detected. A crucial step for the development of an OMBR-based biosensor is constituted by the functionalization of its inner surface. In this work we report on the development of a physical and chemical process able to guarantee a good homogeneity of the deposed bio-layer and, contemporary, to preserve a high quality factor Q of the cavity. The OMBR capability of working as bioassay was proved by different optical techniques, such as the real time measurement of the resonance broadening after each functionalization step and fluorescence microscopy.

Monitoring the quality of high refractive index edible oils is of great importance for the human health. Uncooked edible oils in general are healthy foodstuff, olive oil in particular, however, they are frequently used for baking and cooking. High quality edible oils are made from seeds, nuts or fruits by mechanical processes. Nevertheless, once the mechanical extraction is complete, up to 15% of the oil remains in oil pomace and in the mill wastewater, which can be extracted using organic solvents, often hexane. Optical fiber sensors based on long period fiber gratings (LPFG) have very low wavelength sensitivity when the surround refractive index is higher than the refractive index of the cladding. Titanium dioxide (TiO2) coated LPFG could lead to the realization of high sensitivity chemical sensor for the food industry. In this work LPFG coated with a TiO2 thin film were successfully used for to detect small levels of hexane diluted in edible oils and for real time monitoring the thermal deterioration of edible oils. For a TiO2 coating of 30 nm a wavelength sensitivity of 1361.7 nm/RIU (or 0.97 nm / % V/V) in the 1.4610-1.4670 refractive index range was achieved, corresponding to 0 to 12 % V/V of hexane in olive oil. A sensitivity higher than 638 nm/RIU at 225 ºC was calculated, in the 1.4670-1.4735 refractive index range with a detection limit of thermal deterioration of about 1 minute.

In this paper we discuss a new method to detect low-order aberration with large peak-valley value. This method also depends on wavefront slope measurements but only need measurements of 6 spots, which means that only 6 pieces of lens are used in detective process, and the mathematical algorithm involved in the calculation process is different from zonal or modal estimation used in Shack–Hartmann Wavefront Sensor. To evaluate the accuracy of this method we simulate this optical measurement process by using the Zemax simulation software and Matlab calculation software. Simulation results show that the reconstructed errors of Zernike aberration coefficients are higher for a larger peakvalley (PV) value of wavefront distortions. The maximal errors of aberration coefficients can be keep lower than 1% for aberrations with different combinations of defocus, astigmatism at 0° ,astigmatism at 45° and some high-order terms.. The new measurement method can be used to direct measure low-order aberrations for laser beam with large transverse area and do not need beam contracting system.

The concept of a tunable surface-plasmon resonance system able to switch between imaging and Kretschmann angular resolved systems by exploiting a tunable optical module is presented. This scheme allows to perform complementary measurements (SPR angular resolve and SPR imaging) on the same setup with no moving parts. Furthermore, this switching capability can be used to calibrate the imaging with the angular resolved measurements, to enhance the quality of the image and SPR curve and to change/optimize the penetration depth of the evanescent wave probe at the interface metal/target.

We describe new technologies for a fabrication of microfluidics and micro-optics components for lab-on-a-chip applications based on polydimethylsiloxane. We use combination of direct laser writing (DLW) lithography for channel patterning in photoresist layer with PDMS imprinting process. Unique imprinting and optical properties favors PDMS for fabrication of different microchannels and microlens arrays. This technology allows the fabrication of different PDMS channel structures. Also PDMS based microlens arrays were patterned in photoresist layer by DLW process and also by interference lithography and imprinted in PDMS layer. Spontaneous microlens array based on polystyrene microspheres was also prepared by spin-coating of dispersed microspheres in photoresist and for organized microlens array we used predefined two-dimensional grid prepared by interference lithography. Final structures were investigated by confocal and optical microscope. The prepared PDMS and polystyrene based microdevices can be used in lab-on-a-chip applications in sensing and biological measurements.

The objective of this research is the construction of a structural health monitoring system that uses fiber Bragg grating (FBG) to determine the health of structures. We develop fast FBG interrogator for real-time measurement of the reflected wavelength of a multipoint FBG to monitor the broadband vibration of a structure. This FBG interrogator, which combines a wavelength-swept laser and a real-time measurement system is capable of measuring wavelength within a standard deviation of 2×10^-3 nm or less. We have demonstrated that the FBG interrogator is able to measure vibration that has a resonance frequency of 440 Hz at intervals of 0.1 ms with a multipoint FBG.

We describe a fundamental study on the plasmonic properties and advanced biosensing mechanisms of functionalized graphene. We discuss a specific design using modified carboxyl groups, which can modulate surface plasmon (SP) coupling and provide an advantage for their binding to the sensing layer with high-performance affinity in an immunological reaction. The functionalized graphene-based surface plasmon resonance (SPR) biosensors have three advantages: high performance, high sensitivity, and excellent molecular kinetic response. In the future, functionalized graphene sheets will make a unique contribution to photonic and SPR diagnosis devices. We wish to highlight the essential characteristics of functionalized graphene-based SPR biosensors to assist researchers in developing and advancing suitable biosensors for unique applications.

Spectral interferomeric methods utilizing the interference of polarization modes in a highly birefringent fiber to measure temperature are analyzed experimentally and theoretically. First, we consider an experimental setup comprising a white-light source, a polarizer, a sensing birefringent fiber, an analyzer and a spectrometer. Temperature sensing by this method is based on the wavelength interrogation, that is the position of a chosen spectral interference fringe in a channeled spectrum is measured as a function of temperature. Employing the setup, we carried out temperature sensing in the range from 300 to 370 K when a part of the sensing fiber is exposed to temperature changes. A wavelength shift of a selected spectral interference fringe is measured and the temperature sensitivity reaches −0.11 nm/K. Second, we consider a setup with another interferometer (represented by a polarizer, a birefringent quartz crystal and an analyzer) to increase the sensitivity of the temperature sensing. In this setup, the resultant channeled spectrum is with envelope which shifts with temperature. We analyze the new sensor theoretically and show that temperature sensing is once again possible by using the wavelength interrogation and the temperature sensitivity to be reached is 0.68 nm/K.

Geopolymer matrices represent one of the main sustainable alternatives to ordinary Portland cement (OPC) and other clinker-based blended cements. Real scale applications are limited and a relevant amount of data is still needed to assess the early age and long-term behavior of these systems. Particularly, the early-age monitoring of geopolymers represent a key parameter for mix design optimization. Most of the available methods for the measurement of temperature evolution due to polycondensation kinetics and early age deformations are related to laboratory activities. The upscaling to in situ techniques represents a crucial step toward technological assessment. To this aim, authors propose to use Fiber Bragg Gratings (FBGs) embedded in the geopolymer matrices. Starting from a case study by authors related to the design of externally bonded fiber reinforced geopolymers for strengthening of existing structures, the matrix was optimized in terms of quartz filler content. The measurements carried out by means of FBG sensors allowed to reduce filler content respect to the abovementioned work. Particularly, quartz content can be reduced by 50%. The temperature associated to polycondensation was slightly below 65°C for the three studied systems, limiting the use of designed metakaolin geopolymer to non-massive structures, since thermal cracking could occur, unless further research will be able to assess the viability of retardants. The experimental results confirm that FBG represent an accurate method for simultaneous shrinkage and temperature measurements for geopolymers and the application in real scale structures for remote sensing could help to create database on inner temperatures and early age deformations.

This article demonstrates use of a fiber Bragg grating (FBG) sensor for in situ monitoring of vacuum process with high sensitivity. The sensor head consists of a commercial syringe barrel with plunger, metal spring, pressure chamber, FBG and safeguarding outer tube. The sensor is configured by firmly fixing the FBG between the plunger and the rigid support provided to the safeguarding tube. Under vacuum process the metal spring facilitates the FBG to get strained in axial direction which results in shift of Bragg wavelength of FBG. The Bragg wavelength shift of FBG is found to be linear with respect to vacuum pressure with a linear coefficient of 0.9988. Pressure sensitivity of the sensor is found to be 27 pm/cm Hg. The sensor design is simple, low-cost and has the advantage of all fiber optic sensors.

In this work authors propose to calculate the deflection of planar panels from the longitudinal surface strain measurements by means of FBG (Fiber Bragg Grating) sensors arrays properly bonded to (or embedded in) panels. To this aim a simple post processing analysis of FBG strain measurements is proposed and discussed. The relationship between the longitudinal strain and the vertical deflection is derived by classical beam theory. Indeed, a second derivative relationship exists between the displacement orthogonal to the surface and the strain component parallel to it. In order to know the strain components, FBG sensors have to be applied on both surface of the panel. The usefulness of the proposed technique can find important application in deflection monitoring of a novel detector, micromegas (MM), based on a micro mesh gaseous structure will be installed as a tracking detector in the ATLAS experiment at LHC (Large Hadron Collider) at CERN (European Organization for Nuclear Research) by the end of 2018, during a major upgrade of the experiment. Thus, in order to validate the proposed methodology, measurements of the surface strain and then of the deflection of a relatively miniaturized MM panel prototype have been carried out . Furthermore, preliminar experimental results of the indirect deflection measurements on a full size MM panel (with trapezoidal shape) have been carried out showing that deflection measurements with resolution of few tens of microns can be successfully achieved.

In this work an optical fiber laser with loop configuration was developed for magnetic field measurement. The transducer element is an FBG written in a HiBi fiber whose wavelength is modified using a magnetostrictive material that applies deformation in the presence of the magnetic field. The laser has a bandwidth of 450 MHz and operates in single polarization. A shift of 258.5 pm was observed in the laser operating wavelength for a magnetic field of 17.85 mT. Moreover, a maximum sensitivity of 14.72 pm/mT in the linear regime operation was achieved when increasing the magnetic field. The system provides a narrow emission line that is dependent on the magnetic field magnitude enabling high resolution interferometric measurement schemes. The laser response to AC magnetic fields was also characterized using a passive interferometer with higher sensitivity in the range of 8.32 to 17.93 mT_RMS.

The article is devoted a ring multibeam interferometer. The last few decades such an interferometer is considered as the most promising sensitive element of inertial microoptical angular velocity sensors. All approaches to microoptical angular velocity sensors design are using only amplitude characteristics of interferometer for determining the angular velocity. Our results indicate that one can use the phase characteristics for the same goal. The method measurement of angular velocity with use of the phase and amplitude characteristics of ring interferometer was developed. The paper considers the advantages of using phase characteristic of ring multibeam interferometer.

Blooming of algae and more generally phytoplankton in water ponds or marine environments can lead to hyper eutrophication and lethal consequences on other organisms. The selective recognition of invading species is investigated by automatic recognition algorithms of optical and fluorescence imaging. On one hand, morphological characteristics of algae of microscopic imaging are treated. The image processing lead to the identification the genus of aquatic organisms and compared to a morphologic data base. On the other hand, fluorescence images allow an automatic recognition based on multispectral data that identify locally the ratio of different photosynthetic pigments and gives a unique finger print of algae. It is shown that the combination of both methods are useful in the recognition of aquatic organisms.

In this work we considered Gold and Aluminum thin films coated with additional dielectric layers as sensing platforms. Operation of these sensors is based on measuring shift in the position of the reflectivity dip in angular reflectivity spectrum of the sample. Shift can be caused by changes in the refraction index of either liquid that interacts with sensors surface (refractometric measurements) or thin adjacent biolayer on top of the sensor due to immobilization of the target molecules (biosensing). Calculations based on Fresnel equations and transfer matrix formalism allowed us to make comprehensive analysis of the angular sensitivity, shape of the reflectivity dip and dynamic range of the sensors with different dielectric coatings. Calculations were performed for both cases of bio and refractometric sensing. Results showed different dependence of the sensitivity of Au an Al based sensors upon refraction index of the dielectric coating. For Au-based surface Plasmon resonance sensor up to two times increased sensitivity can be achieved using dielectric coating with high refraction index 2.3 of proper thickness. For sensors based on aluminum we were able to achieve 50% increased angular sensitivity. At the same time width of the reflectivity dip increased proportionally to the optical thickness of the dielectric coating. For estimating sensors quality we analyzed ratio of the angular sensitivity to the width of the reflectivity dip. This ratio decreased with increase in optical thickness of the dielectric, however angular sensitivity of the sensor increased significantly. Deposition of the additional dielectric layer with high refraction index such as Niobium Oxide can also improve chemical and mechanical stability of the sensor.

In the present paper an optical technique is described to measure non-invasively the diameter and refractive index of a transparent (glass or polymer) fiber that possess a circular cross-section. The method is based on an inverse analysis of the rainbow, which is formed by light scattering of low temporal coherency. This enables to achieve unambiguous mathematical relationships between fringe structure of the rainbow and the fiber.

Porous silicon (PSi) non-symmetric multilayers are modified by organic molecular beam deposition of an organic semiconductor, namely the N,N’-1H,1H-perfluorobutyldicyanoperylene-carboxydi-imide (PDIF-CN₂). Joule evaporation of PDIF-CN₂ into the PSi sponge-like matrix not only improves but also adds transducing skills, making this solid-state device a dual (optical and electrical) signal sensor for biochemical monitoring. PDIF-CN₂ modified PSi optical microcavities show an increase of about 5 orders of magnitude in electric current with respect to the same bare device. This feature can be used to sense volatile substances.

An experimental setup for the CO₂ concentration measurement operating at 2.05 μm in pulsed mode and its characterization are presented. The system consists of a light source, which is a tunable laser diode operating in pulse mode. The initial radiation from the diode laser is divided into two parts: the first part of the beam is directed to a retro reflector, and the second part is used for diode output power monitoring. The receiving system consists of a focusing optic and a photodiode. The absorption is determined by comparing the intensities of the detected light on wavelengths absorbed and not absorbed by CO₂ molecules. The prospects of the system change to a differential absorption lidar (DIAL) with a parametric generator as a light source that increases precision and range of generated wavelengths up to 10 μm are outlined.

Sensitive and accurate detection of cancer cells plays a crucial role in diagnosis of cancer and minimal residual disease, so being one of the most hopeful approaches to reduce cancer death rates. In this paper, a strategy for highly selective and sensitive detection of lymphoma cells on planar silicon-based biosensor has been evaluated. In this setting an Idiotype peptide, able to specifically bind the B-cell receptor (BCR) of A20 cells in mice engrafted with A20 lymphoma, has been covalently linked to the sensor active surface and used as molecular probe. The biochip here presented showed a coverage efficiency of 85% with a detection efficiency of 8.5×10^-3 cells/μm². The results obtained suggested an efficient way for specific label-free cell detection by using a silicon-based peptide biosensor. In addition, the present recognition strategy, besides being useful for the development of sensing devices capable of monitoring minimal residual disease, could be used to find and characterize new specific receptor-ligand interactions through the screening of a recombinant phage library.

Traditional stereo imaging technology is not working for dynamical translucent media, because there are no obvious characteristic patterns on it and it’s not allowed using multi-cameras in most cases, while phase space optics can solve the problem, extracting depth information directly from “space-spatial frequency” distribution of the target obtained by plenoptic sensor with single lens. This paper discussed the presentation of depth information in phase space data, and calculating algorithms with different transparency. A 3D imaging example of waterfall was given at last.

The experimental results obtained with two different Plastic Optical Fiber (POF) geometries, tapered and not-tapered, for a sensor based on Surface Plasmon Resonance (SPR) are presented. SPR is used for determining the refractive index variations at the interface between a gold layer and a dielectric medium (aqueous medium). In this work SPR sensors in POF configurations, useful for bio-sensing applications, have been realized for the optimization of the sensitivity and experimentally tested. The results show as the sensitivity increases with the tapered POF configuration, when the refractive index of aqueous medium increases.

The non-reciprocity of magneto-optical reflection response by surface plasmon excitation in the planar Au/Fe/Au/glass nano-systems with prism coupling is studied. These structures are intended as magnetic field sensor units combining magneto-optical (MO) and surface-plasmon-resonance (SPR) effects. The ability of MO-SPR systems to magnetic field sensing is analysed using incidence-angle-depending response function (R_pp ⁽⁺⁾ – R_pp ^(-))/(R_pp ⁽⁺⁾ + R_pp ^(-)), where R_pp denotes the reflectance of p-polarized beam; and, the sign in upper index relates to the orientation of external magnetic field. The proposed sensitivity criteria F and K (the magnitude and inflexed tangent of the response function oscillation) are applied in transverse MO configuration. Mathematical model based on the own matrix algorithm is applied to simulate the diffraction response to varying external magnetic field at the wavelength 632.8 nm. Obtained theoretical results are compared with experiments realized using the measuring device Multiskop (Optrel GbR, Germany).

The interest in graphene–like materials involves many research areas, including the development of biosensors devices. We have recently studied the use of graphene/metal bilayer for surface plasmon resonance (SPR) equipment devoted to detection of chemical processes and biomolecules recognition. The dual role of graphene is to protect the metal layer underneath and to enhance the bioaffinity by adsorbing biomolecules with carbon–based ring structures. Depending on the application, it may be necessary laser and chemical treatments of graphene to improve the performances of the whole device. The processing effects will be investigated by near edge X-ray absorption fine structure (NEXAFS) spectroscopy. The use of synchrotron light is mandatory for NEXAFS analysis since a continuous EUV source of selected polarization is required. The ideas, the analysis and the results are the subjects of this work.

Nanostructured photoluminescent materials are optimal transducers for optical biosensors due to their capacity to convert molecular interactions in light signals without contamination or deterioration of the samples. In recent years, nanostructured biosensors with low cost and readily available properties have been developed for such applications as therapeutics, diagnostic and environmental. Zinc oxide nanowires (ZnO NWs) is material with unique properties and due to these they were widely studied in many fields as electronics, optics, and photonics. ZnO NWs can be either grown independently or deposited on solid support, such as glass, gold substrates and crystalline silicon. Vertical aligned ZnO forest on a substrate shows specific advantages in photonic device fabrication. ZnO NWs are typically synthesized by such techniques classified as vapour phase and solution phase synthesis. In particular, hydrothermal methods have received a lot of attention and have been widely used for synthesis of ZnO NWs. This technique shows more crystalline defects than others due to oxygen vacancies, so as the material shows intense photoluminescence emission under laser irradiation. ZnO NWs surface is highly hydrolysed, so it is covered by OH reactive groups, and standard biomodification chemistry can be used in order to bind bioprobes on the surface. In this work, we present our newest results on synthetic nanostructured materials characterization for optical biosensors applications. In particular, we characterize the ZnO NWs structure grown on crystalline silicon by SEM images and the biomodification by photoluminesce technique, fluorescence microscopy, water contact angle and FT-IR measurements.

Molecular condensation nuclei (MCN) detector is a specialized optical sensor which provides for monitoring of various chemicals impurity in the environment and diagnosis of diseases in human exhaled air ("electronic nose" biosensor). Structurally MCN detector is included in the highly sensitive gas analyzers based on MCN method. The article describes the fundamental principles, specific features and application fields of the advanced highly sensitive MCN method. The MCN method is based on the application of various physico-chemical processes to the flow of a gas containing impurities. As a result of these processes aerosol particle that are about 10⁶ times larger than the original molecule of the impurity are produced. The ability of the aerosol particle to scatter incident light also increases ~10¹⁴÷10¹⁶ times compared with the original molecule and the aerosol particle with the molecule of the impurity in the center is easily detected by light scattering inside a photometer. By measuring of the light scattering intensity is determined concentration of chemical impurities in the air. Aerosol particles in the MCN detector are formed in the condensing devices through overgrowth of the molecule detectable impurity by molecules so-called «developer» substance. At the final stage of the analysis in the MCN detector is measured light scattering by aerosol particles which is proportional to the concentration of determined impurities in the environment. For calculations of the scattered radiation is applicable Mie’s theory considering the scattering of light by spherical particles whose size is comparable to the wavelength of light. We have determined that the light scattering by aerosol particles is interferometric and is comparable within an order of magnitude with light scattering by the air inside a photometer. The detection threshold for the target component of the gas analyzer is attained at the spontaneous ionization background level and not at the limiting sensitivity level of the photodetector.

Extensive attention has been paid to optical fiber microphone because of its especial merits, such as anti-electromagnetic interference, corrosion resistance, high sensitivity, safety and reliability. In the present study, a kind of optical fiber microphone array based on Sagnac interferometer using a broadband source is proposed. On the basis of the high sound quality and wide bandwidth of optical fiber microphones, the acoustic source localization theory is tested and verified in practice. The results prove the possibility of determine the location of acoustic source in a wide range of frequencies accurately. Besides its feasibility, the scientific value and application prospect, such as in battlefield and ultrasonic detection field, are great.

New inversion scheme for gas temperature distribution retrieval utilized CO₂ spectrum between 2350 cm^-1 and 2400 cm^-1 is proposed. Inversion model is build base on neural networks. Considered spectral remote sensing method is commonly used for industrial and environmental monitoring. It is a passive single-ended sensor technique in which radiation intensity emerging from a studied object is analyzed. Quantitative investigation of heated gas radiation emission to determine temperature and gas mixture by infrared spectroscopy requires two components apart from optical radiation sensor. First appropriate spectral database and second efficient inversion techniques. In this study calculation of one-dimensional radiative transfer equation have been used for simulation of spectral radiation intensity. To increase quality of retrieval a spectrum preprocessing and feature extraction method is applied. Simulated spectra were parameterized and expressed as ratios of intensities of multiple rotational lines. Each neural network estimates temperature (NN response) at one point on studied path basing on given spectrum (NN input).

The non-uniform response of the sensors are increasingly prominent with infrared focal plane arrays (IRFPAs) being more and more used in infrared measuring systems, which gives uncorrected images and measurement error. The merits and faults of several non-uniformity correction algorithms attracting broad attention in recent years, including two-point correction, multipoint correction, temporal high pass filter correction (THPFC), artificial neural network correction (ANNC), were analyzed and discussed in this paper. In addition, the algorithm validation has been respectively carried out on these methods, using existing infrared images sequences and the possibility of application of scene-based non-uniformity correction techniques for infrared measuring systems, is discussed by preliminary research and exploration.

Actually during construction of the high building actively are used objects of various nonlinear surface, for example, sinuous (parabolic or hyperbolic) roofs of the sport complexes that require automatic deformation control [1]. This type of deformation has character of deflection that is impossible to monitor objectively with just one optoelectronic sensor (which is fixed on this surface). In this article is described structure of remote optoelectronic sensor, which is part of the optoelectronic monitoring system of nonlinear surface, and mathematical transformation of exterior orientation sensor elements in the coordinates of control points.

This paper presents the method of bending force and temperature measurement. For this purpose, a station with a thermal chamber has been designed and a bracket used in further measurements on which Bragg gratings have been mounted. The performance of simultaneous measurements of force and temperature was possible through the use of an appropriate layout of the sensor. The method of indirect measurements was used, using information deriving from the spectrum of the uniform Bragg gratings, placed on the cantilevers. The measuring system scheme was proposed for measuring sizes measured in the form of bending force, acting in two directions, perpendicular to the grating axis. The increase in the sensitivity of the change on the force is obtained in relation to the system, in which only information on the width of the spectrum of one of the gratings would be used. A change in the spectral width value was observed along with the increase in bending forces from 0 to 10N for two cantilever beams schemes. The head of the sensor can reach larger physical sizes, in exchange enabling a measurement of force and temperature in many places, thus determine the distribution of force and temperature.

Temperature effects on the spectral lines of two Fabry-Perot GaN-based blue laser diodes obtained from Toptica and Roithner Laser Tech are experimentally investigated over the temperature range 5 °C to 60 °C in steps of 0.5 °C. A high resolution monochromator SPEX 1403 with a nominal resolution of 0.003 nm is used in this study. A detailed comparison on the number of modes, mode spacing, emission range and change of emission wavelength per degree Celsius will be presented in this paper. The results of this comparison are used to investigate the suitability of the employment of these laser diodes in open-path detection of NO₂ gas pollution.

High resolution spectral lines study is performed on the emissions of a blue laser diode as a function of applied current. The range of applied current used is between the threshold current of 20 mA and 100 mA with a 0.2 mA increment. With this range of current, the observed emission spectra are between 446 and 448 nm. Typically, 21 longitudinal modes are observed with a mode spacing of 0.05 nm. This mode spacing is found to be in good agreement with the predicted values calculated using the GaN index of refraction and the length of laser cavity. The peak location of each longitudinal mode is measured to shift uniformly with a rate of 0.0045 nm/mA. The intensity and wavelength of each longitudinal mode are observed to be stable over extended period of time. Selected longitudinal modes will be employed to detect traces of pollution gases.

Availability of high intensity light emitting diodes in the blue region offer excellent opportunity for using them in active Differential Optical Absorption Spectroscopy (DOAS) to detect air pollution. Their smooth and relatively broad spectral emissions as well as their long life make them almost ideal light sources for active DOAS. In this study, we report the usage of a blue light emitting diode in an active DOAS setup to measure traces of NO2 gas and achieving few parts per billion detection limit for a path length of 300 m. Details of the setup will be presented along with the effects on measurement accuracy due to shifts in the measured spectra calibration and due to using theoretical instrument Gaussian function instead of the measured instrument function.

Sensor holograms utilize the diffraction principle of transmitting volume holographic grating (VHG) recorded within a photopolymer appositely functionalized to detect a specific stimulus or analyte. A change in the swelling or shrinking state or cross-linking density of the polymer can be caused by the hologram interaction with an analyte. This leads to a change in the recorded hologram sensor and thus, considering an incident monochromatic light and the VHG angular selectivity, to an angle shift of the diffracted maximum intensity. In this work, two new photopolymers based on a sol-gel matrix opportunely functionalized to be sensitive to transition metals or heavy metals were used as sensitive material to record VHGs. An interferometric set up with a laser source at 532nm was used to record VHGs and gratings of 1000 lines/mm were realized. When exposed to a solution of water and lead, an angle shift of about 3° of the first order diffraction of the grating was measured, demonstrating its capability to reveal the presence of heavy metal in water.

We propose and experimentally demonstrate a cable television monitoring system based on a linear-cavity fiber laser and fiber Bragg grating (FBG) sensors. The linear-cavity fiber laser comprises a hybrid amplifier with an erbium-doped fiber amplifier and a semiconductor optical amplifier, a fiber loop mirror with a polarization controller and an optical coupler as a cavity mirror, and the FBG sensors acting as another cavity mirrors. Experimental results showed the feasibility of the monitoring system with sufficient of signal-to-noise ratio over 30 dB and stable output power, and the link of cable television signals on fiber link can monitored in real time. Excellent performances of carrier-to-noise ratio after long-distance transmission are obtained for cable television applications.

In this paper, we propose a novel „gold on gold‟ biosensing scheme for absorbance based fiber-optic biosensor. First, a self-assembled monolayer of gold nanoparticles is formed at the sensing region of the fiber-optic probe by incubating an amino-silanized probe in a colloidal gold solution. Thereafter, the receptor moieties, i.e. Human immunoglobulin G (HIgG) were immobilized by using standard alkanethiol and classic carbodiimide coupling chemistry. Finally, biosensing experiments were performed with different concentrations of gold nanoparticle-tagged analyte, i.e. Goat anti- Human immunoglobulin G (Nanogold-GaHIgG). The sensor response was observed to be more than five-fold compared to the control bioassay, in which the sensor matrix was devoid of gold nanoparticle film. Also, the response was found to be ~10 times higher compared to the FITC-tagged scheme and ~14.5 times better compared to untagged scheme. This novel scheme also demonstrated the potential in improving the limit of detection for the fiber-optic biosensors.