Real time simultaneous measurement by remote laser source of long range longitudinal displacement and small angle wobbling of a sliding target is demonstrated. The compact self-aligned laser-self-mixing interferometer achieves 0.8 µm axial resolution over 1 m linear and 17 µrad of pitch and yaw resolution over 2 mrad angular ranges, respectively.

An innovative quartz enhanced photoacoustic (QEPAS) gas sensing system operating in the THz spectral range and employing a custom quartz tuning fork (QTF) is described. The QTF dimensions are 3.3 cm × 0.4 cm × 0.8 cm, with the two prongs spaced by [similar]800 μm. To test our sensor we used a quantum cascade laser as the light source and selected a methanol rotational absorption line at 131.054 cm−1 ([similar]3.93 THz), with line-strength S = 4.28 × 10−21 cm mol−1. The sensor was operated at 10 Torr pressure on the first flexion QTF resonance frequency of 4245 Hz. The corresponding Q-factor was 74 760. Stepwise concentration measurements were performed to verify the linearity of the QEPAS signal as a function of the methanol concentration. The achieved sensitivity of the system is 7 parts per million in 4 seconds, corresponding to a QEPAS normalized noise-equivalent absorption of 2 × 10−10 W cm−1 Hz−1/2, comparable with the best result of mid-IR QEPAS systems.

Gold nanoparticles stabilized on metal oxide supports have found a wide range of applications especially in heterogeneous catalysis and gas sensing. A facile methodology for the in situ electrodecoration of gold nanoparticles on metal oxide supports is presented herein. Metal oxides such as indium oxide (In2O3) and zirconia (ZrO2) nanoparticles are first prepared via the sol-gel route. Subsequently, gold nanoparticles are electrodeposited in situ on the surface of these metal oxides using a modified sacrificial Au-anode electrolysis procedure. Both pristine as well as electrodecorated metal oxides are characterized by X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), scanning and transmission electron microscopies (SEM, TEM). SEM images of electrodecorated metal oxides reveal successful deposition of gold nanoparticles on metal oxide supports. XPS shows that nano-sized gold is significantly available on the materials' surface and it is in the elemental oxidation state. Moreover, it is found that the electrodecoration of gold nanoparticles on metal oxide surfaces proceeds as a function of the concentration of hydroxyl groups on the surface of metal oxide supports.

The recent development of ultrafast laser ablation technology in precision micromachining has dramatically increased the demand for reliable and real-time detection systems to characterize the material removal process. In particular, the laser percussion drilling of metals is lacking of non-invasive techniques able to monitor into the depth the spatial-and time-dependent evolution all through the ablation process. To understand the physical interaction between bulk material and high-energy light beam, accurate in-situ measurements of process parameters such as the penetration depth and the removal rate are crucial. We report on direct real time measurements of the ablation front displacement and the removal rate during ultrafast laser percussion drilling of metals by implementing a contactless sensing technique based on optical feedback interferometry. High aspect ratio micro-holes were drilled onto steel plates with different thermal properties (AISI 1095 and AISI 301) and Aluminum samples using 120-ps/110-kHz pulses delivered by a microchip laser fiber amplifier. Percussion drilling experiments have been performed by coaxially aligning the diode laser probe beam with the ablating laser. The displacement of the penetration front was instantaneously measured during the process with a resolution of 0.41 mu m by analyzing the sawtooth-like induced modulation of the interferometric signal out of the detector system.

Automobile exhaust gas emissions are causing serious damage to urban air quality in and around major cities of the world, which demands continuous monitoring of exhaust emissions. The chief components of automobile exhaust include carbon monoxide (CO), nitrogen oxides (NOx), and hydrocarbons. Indium zirconate (InZrOx) and gold/indium zirconate (Au/InZrOx) composite nanopowders are believed to be interesting materials to detect these substances. To this end, characterization and gas sensing properties of InZrOx and Au/InZrOx composite nanopowders are discussed. InZrOx nanoparticles with In/Zr atomic ratio of 1.00 (±0.05) are synthesized via pH-controlled co-precipitation of In and Zr salts in aqueous ammonia. Gold (Au) nanoparticles are subsequently deposited on InZrOx using an in situ sacrificial Au electrolysis procedure. The products are characterized by scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS). The gas sensing performance of Au/InZrOx composite nanopowder is studied by depositing a thick powder film on interdigitated electrode structures patterned on SiC substrate to facilitate high temperature operation. The resistivity of the Au/InZrOx layer is the sensor signal, and the sensors could be operated at 500–600 °C, which is a suitable temperature range for engine exhaust measurements. The control sensing measurements reveal that Au/InZrOx composite nanopowder exhibits higher response towards 2–20 % O2 gas as compared to pristine InZrOx nanoparticles. Further studies show that when applied to exhaust gases such as CO and nitric oxide (NO), the response of Au/InZrOx sensors is significantly higher towards NO in this temperature range. Thus, sensor performance characteristics of Au/InZrOx composite nanopowder are promising in terms of their applications in automobile exhaust emission control.

The implementation, performance validation, and testing of a gas-leak optical sensor based on mid-IR quartz-enhanced photoacoustic (QEPAS) spectroscopic technique is reported. A QEPAS sensor was integrated in a vacuum-sealed test station for mechatronic components. The laser source for the sensor is a quantum cascade laser emitting at 10.56 µm, resonant with a strong absorption band of sulfur hexafluoride (SF₆), which was selected as a leak tracer. The minimum detectable concentration of the QEPAS sensor is 2.7 parts per billion with an integration time of 1 s, corresponding to a sensitivity of leak flows in the 10^-9 mbar∙l/s range, comparable with state-of-the-art leak detection techniques.

To monitor the density of photo-generated charge carriers on a semiconductor surface, we demonstrate a detectorless imaging system based on the analysis of the optical feedback in terahertz quantum cascade lasers. Photo-excited free electron carriers are created in high resistivity n-type silicon wafers via low power (ffi40 mW/cm2) continuous wave pump laser in the near infrared spectral range. A spatial light modulator allows to directly reconfigure and control the photo-patterned intensity and the associated free-carrier density distribution. The experimental results are in good agreement with the numerical simulations.

Biosystems integration into an organic field-effect transistor (OFET) structure is achieved by spin coating phospholipid or protein layers between the gate dielectric and the organic semiconductor. An architecture directly interfacing supported biological layers to the OFET channel is proposed and, strikingly, both the electronic properties and the biointerlayer functionality are fully retained. The platform bench tests involved OFETs integrating phospholipids and bacteriorhodopsin exposed to 1–5% anesthetic doses that reveal drug-induced changes in the lipid membrane. This result challenges the current anesthetic action model relying on the so far provided evidence that doses much higher than clinically relevant ones (2.4%) do not alter lipid bilayers’ structure significantly. Furthermore, a streptavidin embedding OFET shows label-free biotin electronic detection at 10 parts-per-trillion concentration level, reaching state-of-the-art fluorescent assay performances. These examples show how the proposed bioelectronic platform, besides resulting in extremely performing biosensors, can open insights into biologically relevant phenomena involving membrane weak interfacial modifications.

We report on a spectroscopic technique named intracavity quartz-enhanced photoacoustic spectroscopy (I-QEPAS) employed for sensitive trace-gas detection in the mid-infrared spectral region. It is based on a combination of QEPAS with a buildup optical cavity. The sensor includes a distributed feedback quantum cascade laser emitting at 4.33 lm. We achieved a laser optical power buildup factor of 500, which corresponds to an intracavity laser power of 0.75 W. CO2 has been selected as the target molecule for the I-QEPAS demonstration. We achieved a detection sensitivity of 300 parts per trillion for 4 s integration time, corresponding to a noise equivalent absorption coefficient of 1.4108 cm1 and a normalized noise-equivalent absorption of 3.21010 W cm1 Hz1/2.

We studied the laser ablation dynamics of steel in the thermal regime both experimentally and theoretically. The real-time monitoring of the process shows that the ablation rate depends on laser energy density and ambient pressure during the exposure time. We demonstrated that the ablation efficiency can be enhanced when the pressure is reduced with respect to the atmospheric pressure for a given laser fluence, reaching an upper limit despite of high-vacuum conditions. An analytical model based on the Hertz-Knudsen law reproduces all the experimental results.

Direct real-time measurements of the penetration depth during laser micromachining has been demonstrated by developing a novel ablation sensor based on laser diode feedback interferometry. Percussion drilling experiments have been performed by focusing a 120-ps pulsed fiber laser onto metallic targets with different thermal conductivity. In-situ monitoring of the material removal rate was achieved by coaxially aligning the beam probe with the ablating laser. The displacement of the ablation front was revealed with sub-micrometric resolution by analyzing the sawtooth-like induced modulation of the interferometric signal out of the detector system.

We analyze the laser self-mixing process in the Gaussian beam approximation and reformulate the expression of the feedback coefficient C in terms of the effective feedback power coupled back into the laser diode. Our model predicts a twenty-fold increase of the ratio between the maximum and the minimum measurable displacements judged against the current plane-wave model. By comparing the interaction of collimated or diverging Gaussian laser beams with a plane mirror target, we demonstrate that diverging beams tolerate larger wobbling during the target displacement and allow for measurement of off-axis target rotations up to the beam angular width. A novel method for reconstructing the phase front of the Gaussian beam by self-mixing scanning measurements is also presented.

An innovative spectroscopic system based on an external cavity quantum cascade laser (EC-QCL) coupled with a mid-infrared (mid-IR) fiber and quartz enhanced photoacoustic spectroscopy (QEPAS) is described. SF6 has been selected as a target gas in demonstration of the system for trace gas sensing. Single mode laser delivery through the prongs of the quartz tuning fork has been obtained employing a hollow waveguide fiber with inner silver–silver iodine (Ag–AgI) coatings and internal core diameter of 300 μm. A detailed design and realization of the QCL fiber coupling and output collimator system allowed almost practically all (99.4 %) of the laser beam to be transmitted through the spectrophone module. The achieved sensitivity of the system is 50 parts per trillion in 1 s, corresponding to a record for QEPAS normalized noise-equivalent absorption of 2.7 × 10−10 W cm−1 Hz−1/2.

We will report here on the design and realization of an optoacoustic sensor for trace gas detection. The sensor consists of a commercial quantum cascade laser and a resonant photoacoustic cell. Two different cell configurations have been investigated: a “standard” H-cell and an innovative T-cell. We will describe the results obtained in the detection of different gases, such as nitric oxide, which plays an important role in environmental pollution and in medical diagnostics, and formaldehyde, a gas of great interest for indoor and outdoor air pollution.

A detailed review on the development of quartz-enhanced photoacoustic sensors (QEPAS) for the sensitive and selective quantification of molecular trace gas species with resolved spectroscopic features is reported. The basis of the QEPAS technique, the technology available to support this field in terms of key components, such as light sources and quartz-tuning forks and the recent developments in detection methods and performance limitations will be discussed. Furthermore, different experimental QEPAS methods such as: on-beam and off-beam QEPAS, quartz-enhanced evanescent wave photoacoustic detection, modulation-cancellation approach and mid-IR single mode fiber-coupled sensor systems will be reviewed and analysed. A QEPAS sensor operating in the THz range, employing a custom-made quartz-tuning fork and a THz quantum cascade laser will be also described. Finally, we evaluated data reported during the past decade and draw relevant and useful conclusions from this analysis.

We report on the instantaneous detection of the ablation rate as a function of depth during ultrafast microdrilling of metal targets. The displacement of the ablation front has been measured with a sub-wavelength resolution using an all-optical sensor based on the laser diode self-mixing interferometry. The time dependence of the laser ablation process within the depth of aluminum and stainless steel targets has been investigated to study the evolution of the material removal rate in high aspect-ratio micromachined holes. (C)2011 Optical Society of America

A general model is proposed for a Vertical Cavity Surface Emitting Laser (VCSEL) with medium aspect ratio whose field profile can be described by a limited set of Gauss-Laguerre modes. The model is adapted to self-mixing schemes by supposing that the output beam is reinjected into the laser cavity by an external target mirror. We show that the self-mixing interferometric signal exhibits features peculiar of the spatial distribution of the emitted field and the target-reflected field and we suggest an applicative scheme that could be exploited for experimental displacement measurements. In particular, regimes of transverse mode-locking are found, where we propose an operational scheme for a sensor that can be used to simultaneously measure independent components of the target displacement like target translations along the optical axis (longitudinal axis) and target rotations in a plane orthogonal to the optical axis (transverse plane). (C) 2012 Optical Society of America

Organic field-effect transistors including a functional bio-recognition interlayer, sandwiched between the dielectric and the organic semiconductor layers, have been recently proposed as ultrasensitive label-free biosensors capable to detect target molecule in the low pM concentration range. The morphology and the structure of the stacked bilayer formed by the protein bio-interlayer and the overlying organic semiconductor is here investigated for different protein deposition methods. X-ray scattering techniques and scanning electron microscopy allow to gather key relevant information on the interface structure and to assess target analyte molecules capability to percolate through the semiconducting layer reaching the protein deposit lying underneath. Correlations between the structural and morphological data and the device analytical performances are established allowing to gather relevant details on the sensing mechanism and further improving sensor performances, in particular in terms of sensitivity and selectivity.

The control of pollutants emission from internal combustion engines is a worldwide issue, in the automotive field. The roadmap for the reduction of vehicle emission limits is driving the academic and industrial interest towards the development of innovative systems integrating novel detection elements and fast feedback circuits and actuators. Based on a tighter control over emissions, and starting from 2014, Euro 6 standards are expected to improve the environmental compatibility of a new generation of vehicles in Europe. This scenario calls for a significant improvement of the sensors technologies for the detection of the main pollutants related to the automotive field, including nitrogen oxides (NOx). In this work, we report on the synthesis and analytical characterization of hybrid nanocomposites containing gold nanoparticles (Au-NPs) and metal oxide nanostructures (MO-NPs, such as zirconium oxide, indium oxide, oxide mixtures, etc.). These species are promising for real-time detection of low levels of NOx species, owing to their low cost, high sensitivity and availability under a variety of stoichiometric and mixing ratios, showing different gas sensing characteristics [1- 2]. Different MO-NPs and mixed MO-NP systems were prepared using a simple but efficient sol-gel method. Subsequently, the nano-oxides were electrodecorated by Au-NPs. Since Au nanophases exhibit pronounced selectivity toward NOx gases [3], the resulting hybrid nanocomposites are expected to improve the nanomaterial sensing performance. All the nanomaterials were characterized using FTIR, XPS, XRD, TEM, and SEM techniques. Experimental evidences support further application of these NPs as active elements in novel NOx sensors.

We report on a quartz-enhanced photoacoustic (QEPAS) gas sensing system for hydrogen sulphide (H₂S) detection. The system architecture is based on a custom quartz tuning fork (QTF) optoacoustic transducer with a novel geometry and a quantum cascade laser (QCL) emitting 1.1 mW at a frequency of 2.913 THz. The QTF operated on the first flexion resonance frequency of 2871 Hz, with a quality factor Q = 17,900 at 20 Torr. The tuning range of the available QCL allowed the excitation of a H₂S rotational absorption line with a line-strength as small as S = 1.13·10⁻²² cm/mol. The measured detection sensitivity is 30 ppm in 3 seconds and 13 ppm for a 30 seconds integration time, which corresponds to a minimum detectable absorption coefficient α(min) = 2.3·10⁻⁷ cm⁻¹ and a normalized noise-equivalent absorption NNEA = 4.4·10⁻¹⁰ W·cm⁻¹·Hz(-1/2), several times lower than the values previously reported for near-IR and mid-IR H₂S QEPAS sensors.

A simple and time-saving wet method to endow the surface of organic semiconductor films with carboxyl functional groups is presented. A thin layer of poly(acrylic acid) (pAA) is spin-coated directly on the electronic channel of an electrolyte-gated organic FET (EGOFET) device and cross-linked by UV exposure without the need for any photo-initiator. The carboxyl functionalities are used to anchor phospholipid bilayers through the reaction with the amino-groups of phosphatidyl-ethanolamine (PE). By loading the membranes with phospholipids carrying specific functionalities, such a platform can be easily implemented with recognition elements. Here the case of biotinylated phospholipids that allow selective streptavidin electronic detection is described. The surface morphology and chemical composition are monitored using SEM and XPS, respectively, during the whole process of bio-functionalization. The electronic and sensing performance level of the EGOFET biosensing platform is also evaluated. Selective analyte (streptavidin) detection in the low pM range is achieved, this being orders of magnitude lower than the performance level obtained by the well assessed surface plasmon resonance assay reaching the nM level, at most.

The detailed action mechanism of volatile general anesthetics is still unknown despite their effect has been clinically exploited for more than a century. Long ago it was also assessed that the potency of an anesthetic molecule well correlates with its lipophilicity and phospholipids were eventually identified as mediators. As yet,the direct effect of volatile anesthetics at physiological relevant concentrations on membranes is still under scrutiny. Organic field-effect transistors(OFETs)integrating a phospholipid (PL) functional biointer-layer(FBI)are here proposed for the electronic detection of archetypal volatile anesthetic molecules such as diethylether and halothane. This technology allows to directly interface a PL layer to an electronic transistor channel,and directly probe subtle changes occurring in the bio-layer. Repeatable responses of PLFBI-OFET to anesthetics are produced in a concentration range that reaches few percent,namely the clinically relevant regime. The PLFBI-OFET is also shown to deliver a comparably weaker response to a non-anesthetic volatile molecule such as acetone

Un sistema misura la tensione di un oggetto. Il sistema include una sorgente laser per generare una radiazione di uscita, una fibra ottica deformabile avente prima e seconda sfaccettatura e mezzi per calcolare una misura di una deformazione della fibra ottica. La prima faccetta è accoppiata alla sorgente laser per ricevere la radiazione di uscita e per trasmettere da essa una radiazione guidata sulla fibra ottica verso la seconda faccetta. La seconda faccetta è atta a ricevere la radiazione guidata e a riflettere una corrispondente radiazione riflessa verso la prima faccetta. La sorgente laser è un tipo di auto-miscelazione atto a ricevere almeno parte della radiazione riflessa e a miscelare la radiazione di uscita con la radiazione ricevuta. ; I mezzi di calcolo calcolano la misura della deformazione della fibra ottica attraverso lo spostamento lineare della seconda sezione misurata dall'effetto di auto-miscelazione nella sorgente laser.

L'invenzione consiste in un transistore “electrolyte gated” che integra uno strato di elementi biologici di riconoscimento in grado di rivelare selettivamente il loro ligando di affinità presente ad una concentrazione nel range dello zepto-molare (10-12 M).

La struttura del dispositivo proposta nella domanda di brevetto no. EP 16207596.4 è stata migliorata per rendere il dispostivo piu’ stabile.

Si tratta di un sensore a transistore, cos’ come del suo array, capace di rivelare, in modo affidabile, selettivo e label-free fino ad una singola molecola di DNA così come di anticorpi e peptidi. noltre il semiconduttore usato è un composito nanostrutturato a base di un polimero semiconduttore, facile da preparare, scalabile ed economico, è anche particolarmente stabile quando impiegato in diretto contatto con l’acqua.

Laser system and method for measuring in real time the variation of the laser ablation depth by means of self-mixing interferometry characterized by a reflecting surface subjected to ablation, a laser diode with an integrated photodiode for the self-mixing signal detecting, a lens for sending a portion of the radiation emitted by the laser diode on the surface subjected to ablation and for sending in the cavity of the laser diode a portion of the radiation emitted by the laser diode and back-reflected by the surface subjected to ablation.

Transistor comprising at least one conductive layer (4), at least one gate dielectric layer (3) and at least one semiconducting film (1) deposited on top of a receptor molecule layer (2) previously deposited or covalently linked to the surface of the gate dielectric (3). Said layer of biological material is constituted by single or double layers of phospholipids, layers made of proteins such as receptors, antibodies, ionic channels and enzymes, single or double layers of phospholipids with inclusion or anchoring of proteins such as: receptors, antibodies, ionic channels and enzymes, layers made of oligonucleotide (DNA, RNA, PNA) probes, layers made of cells or viruses, layers made of synthetic receptors for example molecules or macromolecules similar to biological receptors for properties, reactivity or steric aspects.

Transistor comprising at least one conductive layer, at least one dielectric layer and at least one thin organic semiconductor film and characterized by at least one layer of biological material deposited directly on the surface of the dielectric. Said layer of biological material is constituted by single or double layers of phospholipids, layers made of proteins such as receptors, antibodies, ionic channels and enzymes, single or double layers of phospholipids with inclusion or anchoring of proteins such as: receptors, antibodies, ionic channels and enzymes, layers made of oligonucleotide (DNA, RNA, PNA) probes, layers made of cells or viruses, layers made of synthetic receptors for example molecules or macromolecules similar to biological receptors for properties, reactivity or steric aspects.