This PDF file contains the front matter associated with SPIE Proceedings Volume 8545, including the Title Page, Copyright information, Table of Contents, and the Conference Committee listing.

The optical limiting behaviour of silver nanoparticles with different sizes and shapes is investigated and compared to the optical limiting performances of conventional carbon black suspension. The optical limiting behaviour is characterized by means of nonlinear transmittance and scattered intensity measurements when submitted to a nanosecond pulsed Nd:YAG laser operating at the fundamental or the second harmonic wavelength. We found that the optical limiting effect is strongly particle size dependent, the best performance achieved with the smaller particles. Moreover, it is shown that the surface plasmon resonance is not the main effect responsible for the nonlinear processes. Especially, the particle size and its implication in the backscattering performance is outlined. A stronger backscattered radiation is observed for the 60 nm sized silver particles in comparison with the 580 nm large ones. Alternatively, a stronger scattering in the forward hemisphere is subsequent to nanoparticles whose sizes are significantly greater.

This work investigates properties of surface plasmons on doped metal oxides in the 2-20 μm wavelength regime. By varying the stoichiometry in pulse laser deposited Ga and Al doped ZnO, the plasmonic properties can be controlled via a fluctuating free carrier concentration. This deterministic approach may enable one to develop the most appropriate stoichometry of ZnAlO and ZnGaO in regards to specific plasmonic applications for particular IR wavelengths. Presented are theoretical and experimental investigations pertaining to ZnAlO and ZnGaO as surface plasmon host materials. Samples are fabricated via pulsed laser deposition and characterized by infrared ellipsometry and Hall-effect measurements. Complex permittivity spectra are presented, as well as plasmon properties such as the field propagation lengths and penetration depths, in the infrared range of interest. Drude considerations are utilized to determine how the optical properties may change with doping. Finite element simulations verify these plasmonic properties. These materials not only offer potential use as IR plasmon hosts for sensor applications, but also offer new integrated device possibilities due to stoichiometric control of electrical and optical properties.

This paper, propose a novel approach to access all optical switching performance usable in telecommunications and photonic signal processing circuits by one continuous MMI coupler under a nonlinear regime to achieve the switching at smallest length of Multimode interference waveguide. In past methods, there have been MMI switch with length about a few millimeters, but in this paper an MMI is presented for switching purposes with a length less than 100μm. In this approach, the wave propagation is studied base on MPA method. The nonlinear wave equation in presence of Kerr nonlinear effect is solved as a set of multiple coupled nonlinear equations, so each equations are related to one of guided modes in Multimode waveguide. With ability of calculating the electric field at the outputs channels, we are able to optimize the Multimode waveguide in terms of length. switching is performable with a variation of input intensity or electric field, thus the output fields have been measured with 10⁵ different amounts of input electric fields for each lengths which are switching candidates, then switching operation is appeared in special length with its dependence input electric fields that each electric fields relate to switch the light to bar or cross outputs, this switch is the outstanding proposal for new all optical digital signal processing due to the compact size.

Azobenzene elastomers due to their ability to change the shape under light irradiation have a fascinating potential for technical applications serving as artificial muscles, sensors, microrobots, actuators, etc. The present study deals with the effects of the orientation liquid-crystalline (LC) interactions between the chromophores on the light-induced deformation of azobenzene elastomers. The orientation LC-interactions are taken into account in the framework of the mean-field approximation. Interaction of the chromophores with the light is described by means of an orientation potential which leads to preferable orientation of chromophores perpendicular to the light polarization direction. The statistics of network strands is described in the framework of the Gaussian approach. We consider photo-mechanical properties of azobenzene elastomers which are in the LC nematic state even at the absence of the light. It is shown that the light is able to induce a phase transition form the uniaxial to biaxial state with preferable orientation of chromophores perpendicular to the light polarization direction. The photomechanical behaviour is very sensitive to the chemical structure of network strands: an azobenzene elastomers can elongate (contract) along the polarization direction of the light, if the chromophores are oriented preferably perpendicular (parallel) to the backbones of network strands.

We have recently initiated a research project that aims at understanding how systematic variations of the number and positioning of a given Inter-System Crossing (ISC) promoter (1,4-dibromophenyl) along the Intramolecular Charge Transfer (ICT) axis of chromophores will affect the outcome of singlet oxygen production, and how this effect will be related to the nature of the ICT transition. In this communication, this strategy is discussed and we show that a clear influence of the ISC promoter’s position on the chromophore exists, which can be used both to improve the singlet oxygen generation efficiency of the sensitizer, but also its linear and nonlinear spectroscopic features.

Spectroelectrochemistry provides improved selectivity for sensors by electrochemically modulating the optical signal associated with the analyte. The sensor consists of an optically transparent electrode (OTE) coated with a film that preconcentrates the target analyte. The OTE functions as an optical waveguide for attenuated total reflectance (ATR) spectroscopy, which detects the analyte by absorption. Alternatively, the OTE can serve as the excitation light for fluorescence detection, which is generally more sensitive than absorption. The analyte partitions into the film, undergoes an electrochemical redox reaction at the OTE surface, and absorbs or emits light in its oxidized or reduced state. The change in the optical response associated with electrochemical oxidation or reduction at the OTE is used to quantify the analyte. Absorption sensors for metal ion complexes such as [Fe(CN)₆]^4- and [Ru(bpy)₃]²⁺ and fluorescence sensors for [Ru(bpy)3]²⁺ and the polycyclic aromatic hydrocarbon 1-hydroxypyrene have been developed. The sensor concept has been extended to binding assays for a protein using avidin–biotin and 17β-estradiol–anti-estradiol antibodies. The sensor has been demonstrated to measure metal complexes in complex samples such as nuclear waste and natural water. This sensor has qualities needed for security and defense applications that require a high level of selectivity and good detection limits for target analytes in complex samples. Quickly monitoring and designating intent of a nuclear program by measuring the Ru/Tc fission product ratio is such an application.

The EU FP7 project CUSTOM (Drugs and Precursor Sensing by Complementing Low Cost Multiple Techniques) aims at developing a new sensing system for the detection of drug precursors in gaseous samples, which includes an External Cavity-Quantum Cascade Laser Photo-Acoustic Sensor (EC-QCLPAS) that is in the final step of realisation. Thus, a simulation based on FT-IR literature spectra has been accomplished, where the development of a proper strategy for the design of the composition of the environment, as much as possible realistic and representative of different scenarios, is of key importance. To this aim, an approach based on the combination of signal processing and experimental design techniques has been developed. The gaseous mixtures were built by adding the considered 4 drug precursor (target) species to the gases typically found in atmosphere, taking also into account possible interfering species. These last chemicals were selected considering custom environments (20 interfering chemical species), whose concentrations have been inferred from literature data. The spectra were first denoised by means of a Fast Wavelet Transform-based algorithm; then, a procedure based on a sigmoidal transfer function was developed to multiply the pure components spectra by the respective concentration values, in a way to correctly preserve background intensity and shape, and to operate only on the absorption bands. The noise structure of the EC-QCLPAS was studied using sample spectra measured with a prototype instrument, and added to the simulated mixtures. Finally a matrix containing 5000 simulated spectra of gaseous mixtures was built up.

The requirements in chemical and biochemical sensing with respect to recognition elements, avoiding non-specific interactions, and high loading of the surface for detection of low concentrations as well as optimized detection systems are discussed. Among the many detection principles the optical techniques are classified. Methods using labeled compounds like Total Internal Reflection Fluorescence (TIRF) and direct optical methods like micro reflectometry or refractometry are discussed in comparison. Reflectometric Interference Spectroscopy (RIfS) is presented as a robust simple method for biosensing. As applications, trace analysis of endocrine disruptors in water, hormones in food, detection of viruses and bacteria in food and clinical diagnostics are discussed.

A large number of techniques for drug precursors chemical sensing has been developed in the latest decades. These techniques are able to screen and identify specific molecules even at very low concentration in lab environment, nevertheless the objective to build up a system which proves to be easy to use, compact, able to provide screening over a large number of compounds and discriminate them with low false alarm rate (FA) and high probability of detection (POD) is still an open issue. The project CUSTOM, funded by the European Commission within the FP7, deals with stand alone portable sensing apparatus based on multiple techniques, integrated in a complex system with a complimentary approach. The objective of the project is to achieve an optimum trade-off between opposite requirements: compactness, simplicity, low cost, sensitivity, low false alarm rate and selectivity. The final goal is the realization of an optical sensing platform able to detect traces of drug precursors compounds, such as ephedrine, safrole, acetic anhydride and the Benzyl Methyl Keton (BMK). This is reached by implementing two main sensing techniques: the fluorescence enhanced by the use of specially developed Organic macro-molecules, and a spectroscopic technique in Mid-IR optical range. The fluorescence is highly selectivewith respect to the target compounds, because it is based on properly engineered fluorescent proteins which are able to bind the target analytes, as it happens in an 'immune-type' reaction. The spectroscopic technique is based on the Photo-Acoustic effect, enhanced by the use of a widely Tunable Quantum Cascade Laser. Finally, the sensing platform is equipped with an air sampling system including a pre-concentrator module based on a sorption desorption cycles of a syndiotactic polystyrene polymer.

The detection of explosives and explosive related compounds is a subject of importance in several areas including environmental health, de-mining efforts (land and sea) and security and defence against terrorist activity. The use of electrochemical methods is particularly attractive as many common explosives contain suitable chemical groups to be detected using electrochemical methods. The electrochemical detection of explosives and related compounds in solution using a virtual metal electrode array and differential pulse voltammetry was achieved. The multiple sets of voltammetric data were integrated using multivariate analysis and matched with known substances present in explosives. Seven explosive substances: 2,4-initrotoluene, 2,6-dinitrotoluene, 3,4-dinitrotoluene, 2-nitrotoluene , octogen (HMX), pentaerithrytol tetranitrate (PETN), trinitrotoluene (TNT) and cyclonite (RDX) and a taggant agent 2,3‐dimethyl‐2,3‐dinitrobutane (DMNB) were subjected to analysis using four solid electrodes, namely glassy carbon, silver, gold and platinum in saline aqueous solutions to mimic an aquatic environment. The results obtained in Differential Pulse Voltammetry (DPV) from the different experiments with each electrode were combined to produce a single voltammogram, which was subjected to chemometric analysis using Partial Least Squares (PLS) and Principle Component Analysis Non-Iterative Partial Least Squares (PCA-NIPALS). A combination of the electrochemical signals obtained together with the use of chemometric analysis made it possible to discriminate between explosives and their mixtures and also to quantitate their concentration in saline solutions. These combinations created a mathematical array, which clearly separates the explosives, even if the electrochemical information is buried or mixed with the electrode background noise.

Chemical control is a crucial element for controlling the manufacturing and distribution of illegal narcotics and synthetic substances. This work is focusing on the vapor phase point detection methodology due to its applicability in customs, airport and harbor check point scenarios where inspection of trucks, cars, containers, as well as people and baggage is required. There are several techniques available that are able to screen and identify specific molecules even at very low concentration at laboratory or in controlled environment. However, a portable system which would be simple to use, sensitive, compact, and capable of providing screening over a large number of compounds and discriminate them with low probability of false alarms with short response time scale is still demanded. Our solution is to combine cantilever enhanced photoacoustic spectroscopy with external cavity quantum cascade laser (EC-QCL), which is capable of measuring infrared gas phase spectra of the analyte substances. High sensitivity in a wide dynamic range is achieved with a silicon MEMS cantilever sensor coupled with an optical readout system and high power laser source, which is operating at the fundamental vibrational absorption wavelengths. High selectivity is achieved by measuring the infrared spectra of the sample gas utilizing widely tunable EC-QCL technology and novel signal processing methods. Measurements with the breadboard demonstrator of the described system and detection limit estimation were performed to a selected drug precursor target molecules. The measurement results indicate low ppb-level gas phase sensitivity to selected drug precursor substances also in the presence of typical interfering molecules.

Development of PCB-integrateable microsensors for monitoring chemical species is a goal in areas such as lab-on-a-chip analytical devices, diagnostics medicine and electronics for hand-held instruments where the device size is a major issue. Cellular phones have pervaded the world inhabitants and their usefulness has dramatically increased with the introduction of smartphones due to a combination of amazing processing power in a confined space, geolocalization and manifold telecommunication features. Therefore, a number of physical and chemical sensors that add value to the terminal for health monitoring, personal safety (at home, at work) and, eventually, national security have started to be developed, capitalizing also on the huge number of circulating cell phones. The chemical sensor-enabled “super” smartphone provides a unique (bio)sensing platform for monitoring airborne or waterborne hazardous chemicals or microorganisms for both single user and crowdsourcing security applications. Some of the latest ones are illustrated by a few examples. Moreover, we have recently achieved for the first time (covalent) functionalization of p- and n-GaN semiconductor surfaces with tuneable luminescent indicator dyes of the Ru-polypyridyl family, as a key step in the development of innovative microsensors for smartphone applications. Chemical “sensoring” of GaN-based blue LED chips with those indicators has also been achieved by plasma treatment of their surface, and the micrometer-sized devices have been tested to monitor O2 in the gas phase to show their full functionality. Novel strategies to enhance the sensor sensitivity such as changing the length and nature of the siloxane buffer layer are discussed in this paper.

In the frame of the EU project CUSTOM, a new sensor system for the detection of drug precursors in gaseous samples is being developed, which also includes an External Cavity-Quantum Cascade Laser Photo Acoustic Sensor (ECQCLPAS). In order to define the characteristics of the laser source, the optimal wavenumbers within the most effective 200 cm^-1 range in the mid-infrared region must be identified, in order to lead to optimal detection of the drug precursor molecules in presence of interfering species and of variable composition of the surrounding atmosphere. To this aim, based on simulations made with FT-IR spectra taken from literature, a complex multivariate analysis strategy has been developed to select the optimal wavenumbers. Firstly, the synergistic use of Experimental Design and of Signal Processing techniques led to a dataset of 5000 simulated spectra of mixtures of 33 different gases (including the 4 target molecules). After a preselection, devoted to disregard noisy regions due to small interfering molecules, the simulated mixtures were then used to select the optimal wavenumber range, by maximizing the classification efficiency, as estimated by Partial Least Squares – Discriminant Analysis. A moving window 200 cm^-1 wide was used for this purpose. Finally, the optimal wavenumber values were identified within the selected range, using a feature selection approach based on Genetic Algorithms and on resampling. The work made will be relatively easily turned to the spectra actually recorded with the newly developed EC-QCLPAS instrument. Furthermore, the proposed approach allows progressive adaptation of the spectral dataset to real situations, even accounting for specific, different environments.

In this paper we report a series of side-chain polymers bearing a push-pull azo-moiety, from pseudo-stylbene type molecules. The azobenzene monomer is chemically incorporated through radical copolymerization in: poly(methacrylate), poly(styrene); and poly(oxazoline) matrices. The different classes of azo-polymers are discussed comparatively to one another from the point of view of: solubility, molecular weights, glass transition temperatures and thermal stability, chromophore contents, and as well as from the point of view of their spectral features.

DLC coating by a high transmittance in the infrared region is applied to the IR Optical System window. In order to apply to the window, durability is needed. Depending on the surrounding environment, the coating can come off. In particular, ambient temperature, humidity, may occur because of chemical contamination. If you encounter a problem, the product is not reliable. Existing environment test is insufficient to assess the durability of DLC coating. We have devised an enhanced environment tests, test results could be evaluated DLC coating durability.

Dimensional machining realized by laser beam and/or another concentrated energy sources in metallic targets, is based on melting, vaporisation and expulsion of some quantities of metal as a function of radiation parameters and material nature. In some cases as: drawing plates used for the synthetic wires, fine fuel filters or fuel injectors, for the internal surface of the hole, is prefered more roughness in comparison of the holes, realized by classic piercing. For instance, to realize some textures of simple synthetic fibres or in combination with natural fibres we want to have not a smooth surface, but a rough one because in this way, the texture will be more resistant in the places exposed at different efforts. Concerning the fuel injectors we prefere the same: a rough surface, in order to ensure a better pulverized jet of the fuel. In the same time, when the hole is machined with a concentrated energy: L.B.M., E.B.M. a.s.o. the injector has a longer life. It is not very easy to study the roughness resulted by L.B.M. in a less than 0.2 mm diameter hole. To avoid errors of investigation, authors have experienced on pieces of carbide and alloyed steel which were bored on separate adjacent plans, and in this way, the bored surfaces were not affected by a cutting operation after boring, for such small diameters.

The biopolymer deoxyribonucleic acid (DNA) was first functionalized with the surfactant cetyltrimethylammonium (CTMA) surfactant and then with the Rhodamine 610 dye at its different concentrations. The obtained complexes are well soluble in a number of organic solvents. Regular thin films were obtained by spin coating on glass substrates and their spectroscopic as well as nonlinear optical properties were studied as function of dye concentration. The THG susceptibility increases, within the experimental accuracy, with rhodamine concentration. The measured its relatively large value is due to the two photon contribution. The concentration dependence of χ ⁽³⁾ (−3ω;ω,ω,ω) can be well fitted, within experimental accuracy, by a linear function.