This PDF file contains the front matter associated with SPIE Proceedings Volume 9141, including the Title Page, Copyright Information, Table of Contents, and the Conference Committee listing.

The performance of a fabricated CMOS line sensor based on the lateral drift-field photodiode (LDPD)1 concept is described. A new pixel structure was designed to decrease the charge transfer time across the photoactive area. Synopsys TCAD simulations were performed to design a proper intrinsic lateral drift-field within the pixel. The line sensor was fabricated in the 0.35 μm CMOS technology, and further characterized using a tailored photon-transfer method² and the EMVA 1288 standard³. The basic parameters such as spectral responsivity, photo-response non-uniformity and dark current were measured at fabricated sensor samples. A special attention was paid to charge transfer time characterization⁴ and the evaluation of crosstalk between neighboring pixels – two major concerns attained during the development. It is shown that the electro-optical characteristics of the developed line sensor are comparable to those delivered by CCD line sensors available on the market, which are normally superior in performance compared to their CMOS based counterparts, but offering additional features such as the possibility of time gating, non-destructive readout, and charge accumulation over several cycles: approaches used to enhance the signal-to-noise ratio (SNR) of the sensor output.

A CMOS compatible Ge photodetector (Ge-PD) fabricated on Si substrates has been shown to be suitable for near infrared (NIR) sensing; linear and avalanche detection, in both proportional and Geiger modes have been demonstrated, for photon counting at room temperature [1]. This paper focuses on implementations of the technology for the fabrication of imaging arrays of such detectors with high reproducibility and yield. The process involves selective chemical vapor deposition (CVD) of a ~ 1-μm-thick n-type Ge crystal on a Si substrate at 700°C, followed by deposition of a nm-thin Ga and B layer-stack (so-called PureGaB), all in the same deposition cycle. The PureGaB layer fulfills two functions; firstly, the Ga forms an ultrashallow p⁺n junction on the surface of Ge islands that allows highly sensitive NIR photodiode detection in the Ge itself; secondly, the B-layer forms a barrier that protects the Ge/Ga layers against oxidation when exposed to air and against spiking during metallization. A design for patterning the surrounding oxide is developed to ensure a uniform selective growth of the Ge crystalline islands so that the wafer surface remains flat over the whole array and any Ge nucleation on SiO2 surface is avoided. This design can deliver pixel sizes up to 30×30 μm2 with a Ge fill factor of up to 95 %. An Al metallization is used to contact each of the photodiodes to metal pads located outside the array area. A new process module has been developed for removing the Al metal on the Ge-islands to create an oxide-covered PureGaB-only front-entrance window without damaging the ultrashallow junction; thus the sensitivity to front-side illumination is maximized, especially at short wavelengths. The electrical I-V characteristics of each photodetector pixel are, to our knowledge, the best reported in literature with ideality factors of ~1.05 with I_on/I_off ratios of 10⁸. The uniformity is good and the yield is close to 100% over the whole array.

A switched-capacitor integrator readout circuit for FET-based terahertz (THz) detectors was fabricated in a 0.13 μm standard CMOS technology. The designed readout circuit is suitable for implementation in pixel arrays due to its compact size and power consumption. In order to find the optimum bias point of the FET detector, responsivity, noise equivalent power (NEP) and signal-to-noise ratio (SNR) curves in function of the FET gate voltage (V_G) have been measured for an arbitrary number of 10 accumulation cycles and two different operating clock frequencies. A responsivity peak of 1.8 kV/W was obtained with a clock frequency of 200 kHz, and of 1.3 kV/W at 400 kHz. A minimum NEP of 7.3 nW/√Hz was obtained with a 400 kHz clock frequency, while at 200 kHz the NEP is 8.5 nW/√Hz. The presented THz measurements with 100 accumulation cycles at 200 kHz and 400 kHz clock frequencies show a SNR improvement after each operation cycle, which means 500 and 1000 measurements per second with on-off modulation of the source, respectively. A test structure containing only a FET detector and a bowtie THz antenna was used to evaluate the impact of the readout circuit in the FET THz detection.

A 600 GHz Field Effect Transistor (FET) is implemented in 0.18 um CMOS technology as a THz detector for imaging applications. A total of 4 FET test structures were fabricated and measured for comparison purposes. Each structure is accompanied by an on-chip bow-tie antenna that directly feeds the detector with THz signal. The detectors are characterized by a THz source and a lock-in amplifier at a sensitivity of 100uV. Measurement results indicate the potential of using both these FET configurations as THz detectors in imaging applications. A normalized frequency sweep analysis shows the broadband nature of Source Driven (SD) FET over the Gate Driven (GD) counterpart. However, the GD structures are more responsive than SD structures. The measurement results also indicate that FET structures with smaller widths show higher voltage response than those with smaller widths for a given channel length.

This work describes a novel color pixel topology that converts the three chromatic components from the standard RGB space into the normalized r-g chromaticity space. This conversion is implemented with high-dynamic range and with no dc power consumption, and the auto-exposure capability of the sensor ensures to capture a high quality chromatic signal, even in presence of very bright illuminants or in the darkness. The pixel is intended to become the basic building block of a CMOS color vision sensor, targeted to ultra-low power applications for mobile devices, such as human machine interfaces, gesture recognition, face detection. The experiments show that significant improvements of the proposed pixel with respect to standard cameras in terms of energy saving and accuracy on data acquisition. An application to skin color-based description is presented.

Global shutter image sensors offer significant advantages over rolling shutter imagers but their implementation needs careful consideration. Each pixel needs a storage element on which the signal is stored after the exposure period. To cope with low read noise requirements, it is essential that the pixel can still perform correlated double sampling or CDS. This requires a second memory element in the pixel, so that the reset reference level of the sense amplifier can be read before the charge is dumped onto the sense node. An important specification is the parasitic light sensitivity or shutter efficiency of the pixel. This is a measure how insensitive the memory cell in the pixel is to light. Depending on the pixel architecture, this may be especially difficult in combination with backside illumination. Other important pixel performance parameters related to pixel architecture are read noise and dark current. In this paper we will review global shutter pixel architectures, compare their performances and discuss future developments. We discuss the issues related to global shutter pixels for high dynamic range and backside illumination, and how the most advanced CMOS image sensor process technologies can offer new approaches.

This paper presents our work on a 65k pixel single-photon avalanche diode (SPAD) based imaging sensor realized in a 0.35μm standard CMOS process. At a resolution of 512 by 128 pixels the sensor is read out in 6.4μs to deliver over 150k monochrome frames per second. The individual pixel has a size of 24μm² and contains the SPAD with a 12T quenching and gating circuitry along with a memory element. The gating signals are distributed across the chip through a balanced tree to minimize the signal skew between the pixels. The array of pixels is row-addressable and data is sent out of the chip on 128 lines in parallel at a frequency of 80MHz. The system is controlled by an FPGA which generates the gating and readout signals and can be used for arbitrary real-time computation on the frames from the sensor. The communication protocol between the camera and a conventional PC is USB2. The active area of the chip is 5% and can be significantly improved with the application of a micro-lens array. A micro-lens array, for use with collimated light, has been designed and its performance is reviewed in the paper. Among other high-speed phenomena the gating circuitry capable of generating illumination periods shorter than 5ns can be used for Fluorescence Lifetime Imaging (FLIM). In order to measure the lifetime of fluorophores excited by a picosecond laser, the sensor’s illumination period is synchronized with the excitation laser pulses. A histogram of the photon arrival times relative to the excitation is then constructed by counting the photons arriving during the sensitive time for several positions of the illumination window. The histogram for each pixel is transferred afterwards to a computer where software routines extract the lifetime at each location with an accuracy better than 100ps. We show results for fluorescence lifetime measurements using different fluorophores with lifetimes ranging from 150ps to 5ns.

The characterization of two Single-Photon Avalanche Diodes (SPADs) structures fabricated in CMOS 150nm technology is reported in this paper. The structures are based on a pwell/n-iso junction and differ only for the presence of a polysilicon layer above the guard ring. Each structure is implemented in two different shapes (circular and square) and four sizes (5,10,15 and 20μm). Measurement results show that both average breakdown voltage and non-uniformity decrease with SPAD sizes. The statistical variation of Photon Detection Efficiency (PDE) and its dependence on device size are also reported and discussed. For all the considered device sizes, a PDE non-uniformity lower than 0.5% was measured.

Polymers have become an important material group in fabricating discrete photonic components and integrated optical devices. This is due to their good properties: high optical transmittance, versatile processability at relative low temperatures and potential for low-cost production. Recently, nanoimprinting or nanoimprint lithography (NIL) has obtained a plenty of research interest. In NIL, a mould is pressed against a substrate coated with a moldable material. After deformation of the material, the mold is separated and a replica of the mold is formed. Compared with conventional lithographic methods, imprinting is simple to carry out, requires less-complicated equipment and can provide high-resolution with high throughput. Nanoimprint lithography has shown potential to become a method for low-cost and high-throughput fabrication of nanostructures. We show the development process of nano-structured, large-area multi-parameter sensors using Photonic Crystal (PC) and Surface Enhanced Raman Scattering (SERS) methodologies for environmental and pharmaceutical applications. We address these challenges by developing roll-to-roll (R2R) UV-nanoimprint fabrication methods. Our development steps are the following: Firstly, the proof of concept structures are fabricated by the use of wafer-level processes in Si-based materials. Secondly, the master molds of successful designs are fabricated, and they are used to transfer the nanophotonic structures into polymer materials using sheet-level UV-nanoimprinting. Thirdly, the sheet-level nanoimprinting processes are transferred to roll-to-roll fabrication. In order to enhance roll-to-roll manufacturing capabilities, silicone-based polymer material development was carried out. In the different development phases, Photonic Crystal and SERS sensor structures with increasing complexities were fabricated using polymer materials in order to enhance sheet-level and roll-to-roll manufacturing processes. In addition, chemical and molecular imprint (MIP) functionalization methods were applied in the sensor demonstrators. In this paper, the process flow in fabricating large-area nanophotonic structures by the use of sheet-level and roll-to-roll UV- nanoimprinting is reported.

Optical sensors exploiting Bloch surface waves at the truncation edge of one dimensional photonic crystals are used here as a valid alternative to surface plasmon resonance operating in the Kretschmann-Raether configuration, and commonly adopted for label-free optical biosensing. In order to reduce the Bloch surface waves resonance width and increase the resolution it is desirable to work with one dimensional photonic crystals with as small losses as possible. However this makes that the resonances observed in a single polarization reflection scheme are shallow and difficult to track in a sensing experiment. Here we report on the practical implementation of an angularly resolved ellipsometric optical sensing scheme based on Bloch surface waves sustained by tantalia/silica multilayers. The angular resolution is obtained by a focused illumination at fixed wavelength and detecting the angular reflectance spectrum by means of a CMOS array detector. The experimental results, obtained by using one tantalia/silica multilayer with a defined structure, show that the limit of detection can be pushed below 2.1x10^-7RIU/Hz^1/2.

This paper describes experimental measurement results for photonic crystal sensor devices which have been functionalized for gas sensing applications. The sensor consists of a two dimensional photonic crystal etched into a slab waveguide having a refractive index of 1.7-1.9. Test devices were fabricated from SiON material on silicon / silicon dioxide platform, and also in polymer materials on silicon platform. The inorganic photonic crystals were made using direct write electron-beam lithography and reactive ion etching. The polymeric devices were made by nano-imprint lithography using the SiON structure as the imprint master. The high refractive index polymer was composed of a TiO₂ - UV resin nanocomposite having a nanoparticle fraction between 50 and 60 wt%. This resulted in a tunable refractive index between 1.7 and 1.85. Devices were functionalized for gas sensing applications by coating the surface with a chemical receptor. This responsive layer reacts with the target gas and changes its refractive index. This change causes the angle of out-coupling to change slightly. In this paper we report successful detection of formaldehyde in air at sub ppm levels, and discuss details of chemical functionalization of the PC sensor.

To engineer a cheap, portable and low-power optical gas sensor, incandescent sources are more suitable than expensive quantum cascade lasers and low-efficiency light-emitting diodes. Such sources of radiation have already been realized, using standard MEMS technology, consisting in free standing circular micro-hotplates. This paper deals with the design of such membranes in order to maximize their wall-plug efficiency. Specification constraints are taken into account, including available energy per measurement and maximum power delivered by the electrical supply source. The main drawback of these membranes is known to be the power lost through conduction to the substrate, thus not converted in (useful) radiated power. If the membrane temperature is capped by technological requirements, radiative flux can be favored by increasing the membrane radius. However, given a finite amount of energy, the larger the membrane and its heat capacity, the shorter the time it can be turned on. This clearly suggests that an efficiency optimum has to be found. Using simulations based on a spatio-temporal radial profile, we demonstrate how to optimally design such membrane systems, and provide an insight into the thermo-optical mechanisms governing this kind of devices, resulting in a nontrivial design with a substantial benefit over existing systems. To further improve the source, we also consider tailoring the membrane stack spectral emissivity to promote the infrared signal to be sensed as well as to maximize energy efficiency.

We present in this paper measurements made by quartz enhanced photoacoustic spectroscopy (QEPAS) technique with antimonide laser diodes emitting at 2.3 μm and 3.3 μm. These measurements dedicated to environmental purposes allow us sensitive detection of ethylene and methane. Two experimental setups are reported: a laboratory and brand new compact benches. The detection limits are mentioned.

For absorbing media the concentration may be calculated directly from the optical transmission following the logarithmic dependence given in the Lambert-Beer law. Due to multiple scattering events in oil-water emulsions (e.g. milk, cream, etc.), these exhibit a nonlinear relationship between the attenuation and the oil concentration. We demonstrate that for increasing oil content in oil-water emulsions the attenuation first increases, then levels out, and finally even decreases for a fat content of 60%. Single-wavelength optical transmission measurements are found to be well suited for the in-line monitoring of oil-water emulsions of fat contents below 20%, e.g., for the in-line fat content monitoring of milk. Using experiments and ray-tracing simulations we evaluate system optimization.

Formaldehyde is a volatile organic compound that exists as a gas at room temperature. It is hazardous to human health causing irritation of the eyes, nose and throat, headaches, limited pulmonary function and is a potential human carcinogen. Sources include incomplete combustion, numerous modern building materials and vehicle fumes. Here we describe a simple method for detecting formaldehyde using low resolution non-dispersive UV absorption spectroscopy for the first time. A two channel system has been developed, making use of a strong absorption peak at 339nm and a neighbouring region of negligible absorption at 336nm as a reference. Using a modulated UV LED as a light source and narrowband filters to select the desired spectral bands, a simple detection system was constructed that was specifically targeted at formaldehyde. A minimum detectable absorbance of 4.5 × 10^-5 AU was estimated (as ΔI/I₀), corresponding to a limit of detection of approximately 6.6 ppm for a 195mm gas cell, with a response time of 20s. However, thermally-induced drift in the LED spectral output caused this to deteriorate over longer time periods to around 30 ppm or 2 × 10^-4 AU.

Lead (Pb²⁺) and copper (Cu²⁺) ions are very common pollutants in water which have dangerous potential causing serious disease and health problems to human. The aim of this paper is to determine lead and copper ions in aqueous solution using direct UV detection without chemical reagent waste. This technique allow the determination of lead and copper ions from range 0.2 mg/L to 10 mg/L using UV wavelength from 205 nm to 225 nm. The method was successfully applied to synthetic sample with high performance.

Optical fiber refractometers coated by a nano-scale gold layer constitute a miniaturized counterpart to the Kretschmann prism and enable the exploitation of surface Plasmon resonance (SPR) for accurate (bio)chemical sensing purposes. In this paper, we analyze the impact of the gold coating and the optical fiber cladding thickness on the cladding modes distribution. We focus more particularly on the SPR mode and its subsequent refractometric sensitivity. We clearly demonstrate that the optimum gold thickness for SPR generation lies in the range between 30 and 70 nm. We also report that a decrease of the cladding diameter from 125 μm to 80 μm enhances the refractometric sensitivity by ~20 %. Theoretical investigations obtained with a finite-difference complex mode solver in cylindrical coordinates are corroborated by experimental data. We make use of tilted fiber Bragg gratings (TFBGs) photowritten in the core of a standard singlemode silica fiber to individually interrogate the cladding modes. TFBGs couple light to the fiber cladding in reflection and present a comb-like amplitude transmitted spectrum composed of the core mode resonance (so-called Bragg resonance) and several tens of cladding mode resonances. The Bragg resonance provides temperature-insensitivity while each cladding mode resonance finely probes a given range of surrounding refractive index values. TFBGs were coated with gold using a standard sputtering process. Experiments conducted on gold-coated TFBGs immersed in calibrated liquids finally show that their ultimate refractometric sensitivity is of the order of 550 nm/RIU (refractive index unit).

Bloch surface waves (BSW) propagating at the surface of truncated, one-dimensional crystals are valid candidates to improve sensors based on surface plasmon polaritons, usually referred to as surface plasmon resonance (SPR). The low losses introduced by the dielectric BSW stacks enable to achieve resonance widths much below the ones of SPR, thus proposing improved sensing results. A simplified, bi-linear model of the resonance intensity distribution is applied to estimate the effect of the resonance properties onto the measurement noise. This yields a limit of detection (LoD) that is used to optimize a BSW supporting thin film stack and to quantitatively compare SPR and BSW sensors. The results indicate that an order of magnitude reduction of the LoD is within reach when sufficient sampling of narrow BSW resonances is achieved.

Constantly refined technology of manufacturing increasingly complex photonic crystal fibers (PCF) leads to new optical fiber sensor concepts. The ways of enhancing the influence of external factors (such as hydrostatic pressure, temperature, acceleration) on the fiber propagating conditions are commonly investigated in literature. On the other hand longitudinal strain analysis, due to the calculation difficulties caused by the three dimensional computation, are somehow neglected. In this paper we show results of such a 3D numerical simulation and report methods of tuning the fiber strain sensitivity by changing the fiber microstructure and core doping level. Furthermore our approach allows to control whether the modes’ effective refractive index is increasing or decreasing with strain, with the possibility of achieving zero strain sensitivity with specific fiber geometries. The presented numerical analysis is compared with experimental results of the fabricated fibers characterization. Basing on the aforementioned methodology we propose a novel dual-core fiber design with significantly increased sensitivity to longitudinal strain for optical fiber sensor applications. Furthermore the reported fiber satisfies all conditions necessary for commercial applications like good mode matching with standard single-mode fiber, low confinement loss and ease of manufacturing with the stack-and-draw technique. Such fiber may serve as an integrated Mach-Zehnder interferometer when highly coherent source is used. With the optimization of single mode transmission to 850 nm, we propose a VCSEL source to be used in order to achieve a low-cost, reliable and compact strain sensing transducer.

Fiber optic sensors outperform traditional sensor technologies in fields such as structural health monitoring, vibration and seismic activity monitoring, intrusion detection, and many other applications. Their key advantages include electromagnetic interference immunity, lightweight, small size, multiplexing capabilities, low power consumption, corrosion and high temperature resistance. To meet the demand of more and more challenging optical sensors a new generation of optical fibers, the so-called microstructured optical fibers (MOFs), has appeared. These fibers are composed of a structure of holes surrounding a solid core, which offers a unique design flexibility to optimize their waveguide properties for specific applications. In particular, the design can be optimized to strongly reduce the cross-sensitivity of a sensor to parasitic physical parameters like temperature variations, as is the case for the sensor presented here. Our sensor is based on a Bragg grating inside a temperature independent highly birefringent MOF with a high transverse strain sensitivity, to evaluate vibrations by a polarimetric measurement of the reflection spectrum. This technique takes advantage of the stress-induced phase shift between the two orthogonally polarized fiber eigenmodes. It consists in coupling linearly polarized light through one arm of an optical coupler (50:50) in the sensing optical fiber in which a highly reflective fiber Bragg grating is inscribed. The reflected signal is analysed through a linear polarizer. The optical fiber is crushed by a mechanical transducer designed to transform the vibration into a mechanical stress transversal to the fiber’s axis. The vibration therefore induces a change of the phase modal birefringence that varies in time at the vibration frequency. In this study we show that using standard single-mode fibers to realize the sensor do not provide stable measurements and that using conventional polarization-maintaining fibers lead to a significant cross-sensitivity to temperature. We then show that the use of a specific type of highly birefringent microstructured optical fiber allows temperature independent (up to 120°C) and repeatable vibration measurements.

In this work, our main achievement was to improve the sensitivity of a biosensor - evanescent mode type; hence contributing to the design of a bacteria sensor in water by choosing an appropriate microstructure of Photonic crystal fiber (PCF) and polymer materials.

A photonic crystal fiber (PCF) surface plasmon resonance (SPR) based sensor is proposed and analysed. The proposed sensor consists of microuidic slots enclosing a dodecagonal layer of air holes cladding and a central air hole. The sensor can perform analyte detection using both HE^x ₁₁ and HE^y ₁₁ modes with a relatively high sensitivities up to 4000 nm=RIU and 3000 nm=RIU and resolutions of 2.5×10^-5 RIU^-1 and 3.33×10^-5 RIU^-1 with HE^x₁₁ and HE^y₁₁, respectively, with regards to spectral interrogation which to our knowledge are higher than those reported in the literature. Moreover, the structure of the suggested sensor is simple with no fabrication complexities which makes it easy to fabricate with standard PCF fabrication technologies.

Today fiber Bragg gratings are commonly used in sensing technology as well as in telecommunications. Numerous requirements must be satisfied for their application as a sensor such as the number of sensors per system, the measurement resolution and repeatability, the sensor reusability as well as the sensor costs. In addition current challenges need to be met in the near future for sensing fibers to keep and extend their marketability such as the suitability for sterilization, hydrogen darkening or the separation of strain and temperature (or pressure and temperature). In this contribution we will give an outlook about trends and future of the fiber Bragg gratings in sensing technologies. Specifically, we will discuss how the use of draw tower grating technology enables the production of tailored Bragg grating sensing fibers, and we will present a method of separating strain and temperature by the use of a single Bragg grating only, avoiding the need for additional sensors to realize the commonly applied temperature compensation.

Fiber Bragg grating sensing principle is based on the exact tracking of the peak wavelength location. Several peak detection techniques have already been proposed in literature. Among these, conventional peak detection (CPD) methods such as the maximum detection algorithm (MDA), do not achieve very high precision and accuracy, especially when the Signal to Noise Ratio (SNR) and the wavelength resolution are poor. On the other hand, recently proposed algorithms, like the cross-correlation demodulation algorithm (CCA), are more precise and accurate but require higher computational effort. To overcome these limitations, we developed a novel fast phase correlation algorithm (FPC) which performs as well as the CCA, being at the same time considerably faster. This paper presents the FPC technique and analyzes its performances for different SNR and wavelength resolutions. Using simulations and experiments, we compared the FPC with the MDA and CCA algorithms. The FPC detection capabilities were as precise and accurate as those of the CCA and considerably better than those of the CPD. The FPC computational time was up to 50 times lower than CCA, making the FPC a valid candidate for future implementation in real-time systems.

The use of microwave radiation for curing carbon-fiber reinforced polymer materials (CFRP) can solve the nonhomogeneous heating problems when using conventional techniques based on the use of catalysts and can reduce the processing times. Optical fiber sensors have well-known advantages for Fiber Reinforced Composites (FRC) monitoring. In this paper fiber Bragg gratings (FBGs) are used for online monitoring of the residual stress and distortions produced during the microwave curing process. The CFRP samples are composed by layers of unidirectional carbon fibers and epoxy resin. The results show a very different behavior between the direction of carbon fibers and the perpendicular direction. Results are compared with the conventional processing technique.

This work presents the comparison between the fiber Bragg grating technology and a vibration-measurement technique based on the detection of polarization rotation (polarimetric sensor) in a standard optical fiber, applied to the dynamic structural monitoring of carbon reinforced composites for the automotive industry. A carbon reinforced composite test plate in a 4-layer configuration was equipped with fiber Bragg gratings and polarimetric fiber sensors, then it was mechanically stressed by static and dynamic loads while monitoring the sensors response. The fiber Bragg grating setup exhibited 1.15±0.0016 pm/kg static load response and reproduced dynamic excitation with 0.1% frequency uncertainty, while the polarimetric sensing system exhibited a sensitivity of 1.74±0.001 mV/kg and reproduced the dynamic excitation with 0.5% frequency uncertainty. It is shown that the polarimetric sensor technology represents a cheap yet efficient alternative to the fiber Bragg grating sensors in the case of vibration-monitoring of small structures at high frequency.

Due to their high mechanical and corrosion resistance and their small dimensions, optical fibre sensors and more particularly fibre Bragg gratings have demonstrated their high potential in the composite material field for monitoring purpose when there are placed under constrain, vibration or temperature variation. In this paper, we evaluate the capability of an Optical Backscatter Reflectometer (OBR) to address two configurations of sensors. The first one is with FBGs of different wavelengths distributed along a unique optical fibre. The second one consists in a high number of identical Fibre Bragg Grating (FBG) sensors cascaded in a single optical fibre and embedded in fibre reinforced polymer composites. In this last case, the optical fibre was placed in such a way that the set of FBGs yields a mapping of the flexural strain applied on the composite sample. For this, the Bragg wavelength evolution of the different FBGs subject to flexion (three and four-points bending) is computed from the OBR trace. This equipment being used in these two special FBGs sensors distribution, we compare them and we present advantages and drawbacks of each others.

The in-situ detection of temperature or stresses produced by the thermal spraying process is important for both the optimization of the elaboration conditions and the subsequent service monitoring of these systems. Optical fiber sensors are excellent candidates for this area of application since they can be embedded into the layers of several dissimilar materials of smart structures. This work relates mainly to the process of embedding optical fibers into ceramic coatings and to the characteristics of the embedded fiber. Firstly, thermal flame spraying is chosen as the elaboration process. Next, a thermal model is proposed in order to evaluate the thermal strain variation with the temperature during the elaboration process in the structure. Finally, a microscopic observation of the embedded optical fiber in the ceramic coating is reported, the mechanical adhesion strength of the embedded fiber is evaluated and the results of the optical attenuation change during the elaboration process are given. They show that no significant fluctuation of the optical power transmitted in the fiber is observed.

A PMMA based plastic optical fibre sensor for use in real time radiotherapy dosimetry is presented. The optical fibre tip is coated with a scintillation material, terbium-doped gadolinium oxysulfide (Gd2O2S:Tb), which fluoresces when exposed to ionising radiation (X-Ray). The emitted visible light signal penetrates the sensor optical fibre and propagates along the transmitting fibre at the end of which it is remotely monitored using a fluorescence spectrometer. The results demonstrate good repeatability, with a maximum percentage error of 0.5% and the response is independent of dose rate.

This contribution deals with a feasibility analysis for the development of radiation tolerant fiber optic humidity sensors based on long period grating (LPG) technology to be applied in high-energy physics (HEP) experiments currently running at the European Organization for Nuclear Research (CERN). In particular, here we propose a high-sensitivity LPG sensor coated with a finely tuned titanium dioxide (TiO₂) thin layer (~100 nm thick) through the sol gel deposition method. The sensor characterization in the relative humidity (RH) range [0-75] % at four different temperatures (in the range -10°C - 25°C) was carried out to assess sensor performances in real operative conditions required in typical experiments running at CERN. Experimental results demonstrate the very high RH sensitivities of the proposed device (up to 1.4 nm/%RH in correspondence of very low humidity levels), which turned out to be from one to three orders of magnitudes higher than those exhibited by fiber Bragg grating (FBG) sensors coated with micrometer thin polyimide overlays. The radiation tolerance capability of the TiO₂-coated LPG sensor is also investigated by comparing the sensing performances before and after its exposure to 1Mrad dose of γ-ionizing radiation. Collected results demonstrate the strong potentialities of the proposed technology in light of its future exploitation in HEP applications as robust and valid alternative to currently used commercial hygrometers.

We describe a measurement method to determine the radial distribution of the photoelastic coefficient C in a step-index optical glass fiber. This method is based on the measurement of the retardance profile of a transversally illuminated fiber for increasing tensile load. The radial profile C(r) is obtained from the inverse Abel transform of this retardance profile. We measured three step-index glass fibers with three different core radii. The results suggest that C may be constant across the fiber section and that the mean absolute value of C is slightly larger for glass fibers than for fused silica. Additionally, the shape of the actual refractive index profile can be derived from the retardance measurements.

A novel approach for extrinsic Fabry-Perot interferometer baseline measurement has been developed. The principles of frequency-scanning interferometry are utilized for registration of the interferometer spectral function, from which the baseline is demodulated. The proposed approach enables one to capture the absolute baseline variations at frequencies much higher than the spectral acquisition rate. Despite the conventional approaches, associating a single baseline indication to the registered spectrum, in the proposed method a modified frequency detection procedure is applied to the spectrum. This provides an ability to capture the baseline variations which took place during the spectrum acquisition. The limitations on the parameters of the possibly registered baseline variations are formulated. The experimental verification of the proposed approach for different perturbations has been performed.

Organic light-emitting diodes (OLEDs) are most frequently used for display purposes and while they have also been utilized in sensing applications, their innate compliance has not previously been exploited for these applications. However, in this manuscript it is shown that OLEDs are compatible with microfabrication methods used in the production of micro mechanical devices. In particular it is shown that the compliance of OLEDs can be utilized in, and not limited to, a new generation of opto-mechanical pressure sensors. A fabrication process for a light-modulating pressure sensor is described. Prototypes were fabricated and tested and the response compared to an analytical theory developed by the authors. It is shown with simple circuitry, a resolution of 11.4 Pa up to 350 kPa is attainable using this technology.

The frequency-lock (FL) accuracy of a passive ring resonator optic gyro (PROG), which is closely related to the frequency bias, determines the ultimate measurement precision of the gyro system; therefore it is particularly important to choose a proper frequency bias for the PROG to achieve excellent performance. The best performance of the PROG comes from the optimal signal-noise ratio (SNR), rather than the highest sensitivity. The relations among the SNR affected by the photon shot noise of the photodetector, sensitivity and the frequency bias of the PROG are analyzed in detail for both transmission-type and reflection-type PROGs under Lorentz function approximation in this paper, and the optimal FL frequency bias ranges are discussed. This work provides explicit theoretical guidance for the systematic optimization of the PROG.

The paper considers the possibility to organize the phase measurements of the rotation speed in the ring-shaped single mode passive cavity, supplied by lone power divider (directed coupler).

The evanescent tail of the guided modes can efficiently excite Raman active molecules located in the cladding of a waveguide. Similarly, a significant fraction of the total emitted Stokes power is evanescently coupled to the same mode. Further, the enhancement effects inherent to the waveguide, alongside with the long interaction length, lead to an increased light-matter interaction, resulting in a higher sensitivity as required by spectroscopic applications, especially in the context of Raman spectroscopy. We calculate the spontaneous Raman scattering efficiency as a function of silicon-nitride strip waveguide dimensions and show that under typical conditions, the overall efficiency is approximately two orders of magnitude higher than in confocal configuration in the free space. We also report the experimental demonstration of the use of silicon-nitride based photonic waveguides in a lab-on-a-chip context for Raman spectroscopy. To the best of our knowledge, this is the first demonstration of Raman spectroscopy using photonic waveguides.

When restoring decorative mortar layers on historic façades, professionals need to determine the colour of these finishes in order to select an appropriate repair mortar. Currently, the appearance of these renders is only assessed from a subjective point of view. To match with the aesthetic aspects of the façade, contractors must constantly adjust their repair mortar composition to avoid a patchwork of different colours, which is detrimental for heritage. This time-consuming (trial-and-error) methodology can be excluded by evaluating ‘colour’ with an objective numerical approach. The challenge of the research was to define and evaluate optimal material dependent boundary conditions for measuring the colour of nonhomogeneous mortars. Four samples with different scale of heterogeneity were measured by two spectrocolorimeters, both with a diffuse illumination geometry. The results were plotted in CIE-L*a*b* colour space. By calculating the colour difference (ΔE*), the influence of measuring with or without specular component was evaluated. We discovered the minimal number of measuring points depends on the scale of heterogeneity and the aperture area. The less homogeneous the mortar sample is and the smaller the aperture area, the more unique measuring points are required. Therefore, it is recommended to choose an aperture head of 25 mm or more to reduce the number of measurements, making your work time-efficient. However, in order to obtain accurate measurements on site, a portable optical spectrum analyser can be used with a 6 mm-diameter aperture, a viewing angle of 10°, SCI mode, illumination source D65, considering a minimum of 15 unique measuring points.

This paper describes the processing algorithm methodology and preliminary results from a novel optical-based system for the assessment of chemical and mechanical deterioration of artworks. The FP7 Syddarta Project prototype is composed of two optical channels: 1) a 3D imaging channel which acquires 3D surface data and multiband information in the visible spectral range; 2) an infrared hyperspectral imaging channel in the spectral range 900 to 2500 nm. The processing algorithms developed perform the system calibration, damage detection and chemical deterioration analysis. Both photometric and geometric calibrations have been implemented. The photometric calibration is based on a white reference and intensity map and compensates for variation in light intensities. The geometric calibration is based on planar homographies to determine the interior and exterior orientation of the projector and the two cameras. This is used to map the acquired data of the different sensors into a single reference frame. To acquire 3D data, a set of phase-shifted fringe patterns is projected on the object which are processed by Fourier transform. To identify mechanical deterioration, the acquired 3D cloud of points is meshed and differences in surface normals for a given radius are computed. To analyse the chemical deterioration of the pigments a supervised classification method has been implemented. First of all, spectral data is normalized with the Extended Multiplicative Scatter Correction algorithm. Then, data dimensionality is reduced by applying Principal Component Analysis and classification is done with Support Vector Machine. Results are presented showing the performance of the described algorithms.

Microscopic imaging techniques are usually applied for the inspection of microstructured surfaces. These techniques require clean measurement conditions. Soilings, e.g. dust or splashing liquids, can disturb the measurement process or even damage instruments. Since these soilings occur in the majority of manufacturing processes, microscopic inspection usually must be carried out in a separate laboratory. We present a measurement system which allows for a microscopic inspection and a 3D reconstruction of microstructured surfaces in harsh industrial conditions. The measurement system also enables precise positioning, e.g. of a grinding wheel, with an accuracy of 5 μm. The main component of the measurement system is a CCD camera with a high-magnification telecentric lens. By means of this camera it is even possible to measure structures with dimensions in the range of 30 to 50 μm. The camera and the lens are integrated into a waterproof and dustproof enclosure. The inspection window of the enclosure has an air curtain which serves as a splash guard. The workpiece illumination is crucial in order to obtain good measurement results. The measuring system includes high-power LEDs which are integrated in a waterproof enclosure. The measurement system also includes a laser with a specially designed lens system to form an extremely narrow light section on the workpiece surface. It is possible to obtain a line width of 25 μm. This line and the camera with the high-magnification telecentric lens are used to perform a laser triangulation of the microstructured surface. This paper describes the system as well as the development and evaluation of the software for the automatic positioning of the workpiece and the automatic three-dimensional surface analysis.

This paper investigates the principal idea of a method using two identical laser vibrometers to eliminate pseudo vibrations, occurring as structured noise in laser-vibrometer measurements of angular velocity of a rotating object. The two vibrometers monitor the same surface path on the rotating object, but are separated by a well specified angle. Thus, they are aligned in such a way that they observe the same speckle patterns, but with a relatively time lag given by the angular separation of the vibrometers and the angular velocity of the object. However, any physical variations in angular velocity of the object occur simultaneously at the two vibrometers. Knowing the angular separation between the vibrometers, simple trigonometry can be used to eliminate the pseudo vibrations. These vibrometers are based on cameras, therefore the experiments demonstrate the principle of the method only, and no real time measurements are obtained here.

To the best of our knowledge, proposed is a novel variable depth of field smart imager design using intelligent laser targeting for high productivity multiple barcodes reading applications. System smartness comes via the use of an Electronically Controlled Variable Focal-Length Lens (ECVFL) to provide an agile pixel (and/or pixel set) within the laser transmitter and optical imaging receiver. The ECVFL in the receiver gives a flexible depth of field that allows clear image capture over a range of barcode locations. Imaging of a 660 nm wavelength laser line illuminated 95-bit one dimensional barcode is experimentally demonstrated via the smart imager for barcode target distances ranging from 10 cm to 54 cm. The smart system captured barcode images are evaluated using a proposed barcode reading algorithm. Experimental results after computer-based post-processing show a nine-fold increase in barcode target distance variation range (i.e., range variation increased from 2.5 cm to 24.5 cm) when compared to a conventional fixed lens imager. Applications for the smart imager include industrial multiple product tracking, marking, and inspection systems.

An electrooptic transduction is here used to perform a low invasive characterization of the magnetic field in the context of magnetic resonance imaging. A resonant coil is coupled to a passive electrooptic crystal and the electromotive force of the magnetic field sensor is converted into a polarization state modulation of a laser probe beam. The optical conversion is demonstrated and lead to a fiber remote measurement of the magnetic field. The setup sensitivity and dynamics are finally dramatically enhanced using a LiNbO3 integrated waveguide. The minimum detectable field is as low as 60 fT.Hz^-1/2 and the dynamics exceeds 100 dB.

Triangulation-based laser line profile sensing is a widely used technique for precise and fast 3D measurement in industrial applications. More recently, it is used for applications in the area of outdoor agricultural sensing as well. However, in many agricultural applications high resolution range data by itself is insufficient. There is also a strong need for local spectral intensity information. As a consequence the combination of image-based range scanners with spectral imaging is often necessary. Under varying environmental conditions this is a tedious and error-prone problem, though. In contrast, the novel approach shown here allows capturing range data along with spectral laser reflectance and pixel-wise backscattering information at multiple, selectable wavelengths using a single sensor system. The system consists of multiple continuous wave (CW) line lasers simultaneously captured by a single monochrome imager. A system ready to capture 3 line lasers at 100 Hz was set up. Line lasers at different wavelengths in the visible and NIR range can be combined in accordance with the requirements of a specific application. Consecutively captured images are matched using sum of absolute differences (SAD) in order for tracking relative movement between the sensor system and the analyzed object. This allows normalizing images before the evaluation of reflectance and scattering. Furthermore, the SAD-based matching is used for accurate assembly of range and reflectance information gathered from different laser lines. It results in 3D point clouds with spectral laser reflectance and backscattering information at multiple, selectable wavelengths available for each point.

Fluorescence LIght Detection And Ranging (LIDAR) systems have been proven powerful for detecting and recognizing underwater objects in several applications. Such Fluorescence systems have been employed mainly for detecting and recognizing oil spill and chemicals dissolved in the sea and to identify phytoplankton species. This work focuses on the use of Fluorescence LIDAR systems in underwater object recognition applications. In fact, the fluorescence spectra induced over object and materials may be exploited to derive chemical-physical information about object nature useful to recognition. Specifically, a model for fluorescence LIDAR transmission in the water medium, both in the presence and absence, of an underwater object is proposed. The developed model describes the interaction of the transmitted laser beam with underwater objects, bottom, and water molecules. Specifically, the fluorescence return signals are modeled involving the inelastic backscattering contributions due to the Raman scattering by water molecules and fluorescence by water constituents, bottom, and objects. A range of simulations have been performed modeling the immersion of an object at different depths within the water column for a variety of system characteristics and water environmental conditions. Simulation results show the model flexibility for reproducing the signals acquired in different operational scenarios on the basis of various system parameters, acquisition geometries, and water environments. The transmission model may be useful to predict the performance of a given fluorescence LIDAR in specific underwater object detection and recognition applications.

Nowadays larger horizontal axis wind turbines (HAWT) are setup in difficult to access locations adding an overhead to the production cost as well as the Operation & Maintenance (O&M) costs. In order to cover those overhead cost, Lidar assisted preview control of wind turbine blade pitch system is prosperous both on research and industry applications. However, there are not a lot of choices to remote sense the wind field inflow. Doppler wind Lidar systems have been proved to be advantageous on such applications. However due to the economical consideration, the state-of-the-art wind Lidar systems are only limited on research. Therefore, developing a cost efficient wind Lidar to support the pitch control of HAWT to reduce the material requirement, lower the O&M cost and decrease the cost of energy (COE) in the long term is our motivation. Our current main focusing of investigations has been laid on the optical design of emitting and receiving system, and the evaluation of the low cost laser system instead of using a high cost fiber laser as a transmitter. The short coherence length lasers brings a higher phase noise into the detection, normally it is not used for the coherent Lidars system. However, such a laser can achieve a higher output power with a low cost which is very important for the market. In order to bring such kind of laser into the application, different sending, receiving, and detection design is simulated and tested. Those testing results are presented in this paper.

In this paper, the sugar content prediction determination system in optical non-contact type based on the near infrared light emitting diode (NIR-LED) lamp is proposed. As the result NIR-LED lamp reduced 86% of the energy consumption compared to the case of Halogen lamp in the same process of sugar content determination. And the result of prediction of sugar content by NIR-LED lamp is shown to as near the same level of Halogen lamp system.

The time-stretch dispersive Fourier transform enables high-throughput acquisition of optical spectra in single-shot measurements by performing an analog Fourier transform and stretching the signal to facilitate capture with high-speed electronics. The coherent time-stretch transform adds complex-field detection so that spectral amplitude and phase can be measured in the temporal near field, i.e., without a strict dispersion requirement. Full-field spectra are recovered via temporal interferometry on waveforms dispersed in the temporal near field. Real-time absorption spectra including both amplitude and phase information are acquired at 37 MHz.

A simple seismic vibration sensor is designed using fiber Bragg grating (FBG) with aid of an inverted spring-mass system. An inertial mass is attached to the spring enables to oscillate in axial direction only when it is subjected to seismic vibration (P-wave). The spring mass system facilitates free motion only in one direction that is parallel to the base. An interrogation system is developed using Single mode-Multimode- Single mode (SMS) configuration to monitor the Bragg wavelength shift of FBG into its equivalent optical intensity modulation corresponding to the seismic vibration. The experimental results show that proposed sensor is capable of measuring the vibrations of frequency over the range of 2-20Hz. Further, it is evident from the results that the sensor is highly sensitive at 7.5Hz represents the resonance frequency of the designed sensor system. The range of the frequency measurement can be optimized by changing the spring parameters or overhead weight (mass) and also the position of the FBG attached between the spring and support. Thus designed sensor head enables low-cost measurement and fast response in real time applications.

This paper introduces an all-optical, fiber-optics vacuum sensor, which takes advantage of the thermo-optic effect within vanadium-co-doped fiber. This sensor utilizes a 980 nm pump-diode and a short section of highly absorbing vanadiumco- doped fiber produced by the flash vaporization process. The 980 nm source operates in pulse mode therefore the vanadium-co-doped fiber is periodically heated and self-cooled. The 980 nm pump-light is fully absorbed within the codoped fiber’s core and relaxed as a heat, which changes the fiber’s core refractive index. The heat-transfer between the heated fiber and surrounding gas depends on the gas pressure. Further, the doped-fiber is inserted into a Fabry-Perot interferometer which forms, in combination with a DFB laser diode at 1550 nm, a high coherence interferometer for optical path-length measurement. The time constant and absolute modulated optical path of the step response can be directly correlated with the gas pressure. The time constant is independent of the pump-diode’s optical power, while the absolute modulated optical path also depends on the pump-diode’s output of optical power and should thus be compensated. The vacuum sensor allows for a remote and fully dielectric measurement of the gas pressure and can be used in various industrial applications.

Luminescent optical fibers doped with silver molecular clusters or cadmium chalcogenide quantum dots were synthesized and investigated. The fibers have a wide spectral sensitivity range required for detection of UV and shortwave visible radiation and high efficiency of waveguide modes excitation. They also can be used as electric arc and spark detectors and for temperature measurement.

A simple and low-cost optical setup can be used for monitoring online the condition of lubricant oil in big machineries, as an action of preventive maintenance. The total acid number and the water content, as indicators of the lubricant oil quality, can be assessed by means of an integrating sphere for achieving scattering-free absorption measurements. For each indicator, spectroscopy showed that a peculiar wavelength is enough for predicting with good accuracy the value of the indicator.

The determination of the physical state of the lubricant materials in complex mechanical systems is highly critical from different points of view: operative, economical, environmental, etc. Furthermore, there are several parameters that a lubricant oil must meet for a proper performance inside a machine. The monitoring of these lubricants can represent a serious issue depending on the analytical approach applied. The molecular change of aging lubricant oils have been analyzed using an all-standard-components and self-designed FT-Raman spectrometer. This analytical tool allows the direct and clean study of the vibrational changes in the molecular structure of the oils without having direct contact with the samples and without extracting the sample from the machine in operation. The FT-Raman spectrometer prototype used in the analysis of the oil samples consist of a Michelson interferometer and a self-designed photon counter cooled down on a Peltier element arrangement. The light coupling has been accomplished by using a conventional 62.5/125μm multi-mode fiber coupler. The FT-Raman arrangement has been able to extract high resolution and frequency precise Raman spectra, comparable to those obtained with commercial FT-Raman systems, from the lubricant oil samples analyzed. The spectral information has helped to determine certain molecular changes in the initial phases of wearing of the oil samples. The proposed instrument prototype has no additional complex hardware components or costly software modules. The mechanical and thermal irregularities influencing the FT-Raman spectrometer have been removed mathematically by accurately evaluating the optical path difference of the Michelson interferometer. This has been achieved by producing an additional interference pattern signal with a λ= 632.8 nm helium-neon laser, which differs from the conventional zero-crossing sampling (also known as Connes advantage) commonly used by FT-devices. It enables the FT-Raman system to perform reliable and clean spectral measurements from the analyzed oil samples.

Laser sensing can serve as a highly effective method of searching and monitoring of radioactive contamination. The first method is essence consists in definition the Sr⁹⁰ and Сs¹³⁷ concentration by excitation and registration of fluorescence at wavelength of λ = 0.347÷7.0 μm at laser sounding. The second method experiments were carried out under the Raman-scattering circuit. Preliminary results of investigation show the real possibility to register of leakage of a radionuclide with concentration at level of 10⁸÷10⁹ сm^-3 on a safe distance from the infected object.

Role of nitrogen oxide in ambient air is described and analyzed. New method of nitrogen oxide concentration measurement in gas phase is suggested based on ozone concentration measurement with titration by nitrogen oxide. Research of chemiluminescent sensor composition is carried out on experimental stand. The sensor produced on the base of solid state non-activated chemiluminescent composition is applied as ozone sensor. Composition is put on the surface of polymer matrix with developed surface. Sensor compositions includes gallic acid with addition of rodamine-6G. Model of interaction process between sensor composition and ozone has been developed, main products appeared during reaction are identified. The product determining the speed of luminescense appearance is found. This product belongs to quinone class. Then new structure of chemiluminescent composition was suggested, with absence of activation period and with high stability of operation. Experimental model of gas analyzer was constructed and operation algorithm was developed. It was demonstrated that developed NO measuring instrument would be applied for monitoring purposes of ambient air. This work was partially financially supported by Government of Russian Federation, Grant 074-U01

Research on sensors has experienced a noticeable development over the last decades especially in label free optical biosensors. However, compact sensors without markers for rapid, reliable and inexpensive detection of various substances induce a significant research of new technological solutions. The context of this work is the development of a sensor based on easily integrated and inexpensive micro-resonator (MR) component in integrated optics, highly sensitive and selective mainly in the areas of health and food. In this work, we take advantage of our previous studies on filters based on micro-resonators (MR) to experiment a new couple of polymers in the objective to use MR as a sensing function. MRs have been fabricated by processing SU8 polymer as core and PMATRIFE polymer as cladding layer of the waveguide. The refractive index contrast reaches 0.16 @ 1550 nm. Sub-micronic ring waveguides gaps from 0.5 to 1 μm have been successfully achieved with UV (i-line) photolithography. This work confirms our forecasts, published earlier, about the resolution that can be achieved. First results show a good extinction coefficient of ~17 dB, a quality factor around 10⁴ and a finesse of 12. These results are in concordance with the theoretical study and they allow us to validate our technology with this couple of polymers. Work is going on with others lower cladding materials that will be used to further increase refractive index contrast for sensing applications.

The improved autocollimation sensors for measuring angular deformations of the large constructions as elevation axle and the azimuth columns of the radio telescopes are analyzed. Two new types of the reflector for autocollimation sensors are researched. The first type of the reflector is the composition of the anamorphic prism and ordinary cube-corner retroreflector. This reflector generates the narrow beam, as result the work distance and the range of measurement of the sensor increases. The second type of the reflectors is the tetrahedral reflector with flat reflecting sides and invariant axis. For this reflector the small value of the conversion coefficient is the realization of the measurements on the large work distances. The technical characteristics of the experimental setups of new reflectors are presented. The features of the anamorphic prism and tetrahedral reflector as the reflectors for autocollimation angular sensors are discussed.

Knowing a thermal expansion coefficient and measured exact thermal expansion, it is possible to design a very sensitive sensor measuring temperature differential. A Michelson interferometer is used to determine temperature changes. It measures linear expansion on a metal object, e.g. a copper rod, as a change in length in response to a change in temperature. Based on the obtained interferograms and knowing the value of thermal expansion coefficient, temperature differential can be calculated. The accuracy of the procedure can be determined by using the exact differential method based on the measurement errors for linear expansion, and initial length. The contribution of this paper is the employment of Michelson interferometer to design a very sensitive differential thermometer measuring with the accuracy of one thousandth degree Celsius. It results from the achieved precision of measuring the optical path length changes in the range of hundreds nanometers. The advantage of this sensor is its precision and noncontact procedure.

We developed a Raman lidar with ultraspectral resolution for automatic airborne monitoring of pipeline leaks and for oil and gas exploration. Test flights indicate that a sensitivity of 6 ppm for methane and 2 ppm for hydrogen sulfide has been reached for leakage detection.

For today the mineral resources of our planet, especially mineral raw deposits are depleted continuously. Therefore the traditional technologies of extraction and enrichment of mineral raw materials are often unable to provide the profitability of development of mentioned mineral deposits. Thus, the mining industry needs in improving of the existing systems for mineral raw materials separation. The well-known optical sorting method is the most promising in terms of improving of structure and characteristics of devices that realize this method. There are a lot of types of color sorters, but they have a number of shortcomings relating to both schemes of lighting and registration of mineral objects as well as used algorithms of images processing. Often color sorters are unable to divide low-contrast small size mineral objects. This problem can be solved by using of optoelectronic complex for separation of moving small size mineral objects developed by the employees of the chair of optical-electronic devices and systems of University ITMO in Russia. The paper presents the description of structure organization and operating principles of proposed experimental model of optoelectronic complex for separation of moving small size mineral objects.

The feature size of the CMOS processes decreased during the past few years and problems such as reduced dynamic range have become more significant in voltage-mode pixels, even though the integration of more functionality inside the pixel has become easier. This work makes a contribution on both sides: the possibility of a high signal excursion range using current-mode circuits together with functionality addition by making signal amplification inside the pixel. The classic 3T pixel architecture was rebuild with small modifications to integrate a transconductance amplifier providing a current as an output. The matrix with these new pixels will operate as a whole large transistor outsourcing an amplified current that will be used for signal processing. This current is controlled by the intensity of the light received by the matrix, modulated pixel by pixel. The output current can be controlled by the biasing circuits to achieve a very large range of output signal levels. It can also be controlled with the matrix size and this permits a very high degree of freedom on the signal level, observing the current densities inside the integrated circuit. In addition, the matrix can operate at very small integration times. Its applications would be those in which fast imaging processing, high signal amplification are required and low resolution is not a major problem, such as UV image sensors. Simulation results will be presented to support: operation, control, design, signal excursion levels and linearity for a matrix of pixels that was conceived using this new concept of sensor.

Modern astronomic telescopes take advantage of multi-conjugate adaptive optics, in which wavefront sensors play a key role. A single sensor capable of measuring wavefront phases at any angle of observation would be helpful when improving atmospheric tomographic reconstruction. A new sensor combining both geometric and plenoptic arrangements is proposed, and a simulation demonstrating its working principle is also shown. Results show that this sensor is feasible, and also that single extended objects can be used to perform tomography of atmospheric turbulence.

The digital holographic interferometry methods that are used in this work nowadays is widely applied to research of temporal dynamics of objects transformation in different processes [1, 2]. Authors use developed stand and software that are used for detecting and controlling of phase changes of transparent objects with time resolution not less than 100 ms for a long time. Samples of recording polymer material for volume holography «Difphen», solid solution of organic dye phenanthrenequinone (PQ) in polymethylmethacrylate (PMMA), were used as an object of research. Samples were prepared in the shape of plane-parallel disks, 40 mm in diameter and thickness (2÷4) mm [3]. The using radiation with wavelength λ=473 nm is located in the region of absorption of PQ and presents by itself a beam of radiation of solid state DPSS laser which is (2.5÷3.0) mm in diameter and its power is of about 50 mWt. The part of the sample that was exposed by the radiation, absorbing energy, is bleaching and heating up. The bleaching process takes place just in localized area (exposed area), while increase of temperature from exposed area to unexposed areas of the sample is spread by heat transfer. For observation of the process of transfer of heat in the quality of probe radiation we use radiation with wavelength λ = 532 nm in spectral area of light-insensitivity the sample. The probe area was 20x20 mm, which allowed us to evaluate thermal effects in object’s area, located out of reach of laser beam 473nm.

Supersonic gas jets can be used as a profile monitor for charged particle beams, as well as a cold target for collision experiments. For the optimisation of these experiments, it is important to know the velocity and density distribution of the jet. In these applications, gas jet velocities can be up to 2000 m/s. A diode laser velocimeter based on laser self-mixing method is currently being developed as an easy to build and compact alternative measurement technique. The technique seems a promising way for a complete characterisation of the gas jet parameters. It should be pointed out, however, that laser self-mixing is usually used for measurement of low velocities and vibrations. In this contribution, the heterodyne principle and design of the laser diode velocimeter are first discussed. The laser velocimeter is a self-aligning device, based on the self-mixing method where the laser is both, transmitter and receiver of the signal. The here presented theoretical analysis shows the possibility to extend measurement capabilities also to high velocities by altering the design. Experimental results from measurements with different targets are presented. The set-up for testing the sensor allows investigations into the limitation of the method to be made as well as the amount of feedback which is required for a detailed study of a gas jet.

In this paper, compact three trenched channel plasmonic microring resonator sensor (TTCP-MRRS) on a silicon-oninsulator substrate is proposed and analyzed. The three trenched waveguide is composed of three metal-gaps-silicon structure, where the optical energy is greatly enhanced in the narrow gaps. The full vectorial finite element method is used to numerically analyze the device optical characteristics as a biochemical sensor. As the optical field in the proposed structure has a large overlap with the upper-cladding sensing medium, the sensitivity is very high compared to other dielectric microring resonator sensors. The sensitivity is the ratio between the resonance wavelength shift and the cladding refractive index change, which is a key parameter to describe the sensor performance. The detection limit (DL), which is defined as the minimum refractive index change in the sensing medium that can be detected by the sensor system, is proportional to the resonance line width Δλ or inversely proportional to the resonance Q-factor. So, in order to properly evaluate the sensing performance of the proposed channel plasmonic microring resonator sensor, a figure of merit (FOM) can be defined as the number of resonance line width shift in response to a unit cladding refractive index change. The proposed (TTCP-MRRS) has a compact size and high sensitivity and can be integrated in an array form on a chip for highly-efficient lab-on-chip biochemical sensing applications.

A temperature independent high sensitive pressure sensing system using fiber Bragg grating (FBG) and ‘C’ shaped Bourdon tube (CBT) is demonstrated. The sensor is configured by firmly fixing the FBG (FBG1) between free and fixed ends of the CBT. Additional FBG (FBG2) in line to the FBG1 is introduced which is shielded from the external pressure, tend to measure only the ambient temperature fluctuations. The CBT has an elliptical cross section where its free end is sealed and the fixed end is open for subjecting the liquid or gas pressure to be measured. With the application of pressure, the free end of CBT tends to straighten out results in an axial strain in FBG1 causes red shift in Bragg wavelength. The pressure can be determined by measuring the shift of the Bragg wavelength. The experimental pressure sensitivity is found to be 66.9 pm/psi over a range of 0 to 100 psi. The test results show that the Bragg wavelength shift is linear corresponds to change in applied pressure and well agreed with the simulated results. This simple and high sensitive design is capable of measuring static/dynamic pressure and temperature simultaneously which suits for industrial applications.