PPG embedded system for blood pressure monitoring

In this work, we have designed and implemented a microcontroller-based embedded system for blood pressure monitoring through a PhotoPlethysmoGraphic (PPG) technique. In our system, it is possible to perform PPG measurements via reflectance mode. Hardware novelty of our system consists in the adoption of Silicon PhotoMultiplier detectors. The signal received from the photodetector is used to calculate the instantaneous heart rate and therefore the heart rate variability. The obtained results show that, by using our system, it is possible to easily extract both the PPG and the breath signal. These signals can be used to monitor the patients during the convalescence both in hospital and at hom…

Sorgente laser multilinea NIR-RGB in guide ottiche RPE su Nd:LiNbO3

One diode circuital model of light soaking phenomena in Dye-Sensitized Solar Cells

Abstract In this work, we report on the modelling of light soaking effect on Ruthenium-based Dye Sensitized Solar cells (DSSCs). Such a phenomenon can be detected when exposing the cells at increasing hours of illumination and produces a reversible performance increase. Starting from the results obtained through the electro-optical characterization of the cells, we applied a one-diode circuital-model. Our results show a good agreement between the experimental and the simulated data, with a mean square error in the order of 10−12 and a maximum error in current lower than 0.6%. Finally such results allowed us to infer some precise trends followed by the cells main electrical parameters and of…

Rateless codes mitigation technique in a turbulent indoor Free Space Optics link

Free Space Optics (FSO) links are affected by several impairments and, among them, optical turbulence is the most important factor that can degrade the link quality. Due to the presence of this phenomenon, the signal irradiance detected by the receiver fluctuates, thus causing erasure errors and fading events. In this work, we present an indoor Free Space Optics link, in which several turbulence conditions are generated by using two heating elements. We show that the generated turbulence causes erasure errors and packet losses during the data transmission, and we also compare the statistical distribution of the samples with the theoretical models. Moreover, we demonstrate how the applicatio…

Photoelectric valuation of highly efficient Dye-Sensitized Solar Cells

Nowadays, a growing demand for free and clean energy requires the study and the development of new low-cost solar photovoltaic (PV) cells. Among them, Dye Sensitized Solar Cells (DSSCs) based on ruthenium complexes as sensitizers are assuming a great importance. The DSSCs under study are composed placing in succession a transparent conductive glass on which is screen-printed a mesoporous TiO2 thin film sensitized by a ruthenium based dye (N719) , an electrolytic solution containing a redox couple (I-/I3-) and another conductive glass covered by a thin transparent catalyst platinum film. In this work, we have measured the main photoelectrochemical parameters of the above mentioned DSSCs at d…

Ion Plating Plasma Assisted Deposition from Thermal Sources for Decorative Coatings

P-on-N and N-on-P silicon photomultipliers: responsivity comparison in the continuous wave regime

We report the electrical and optical comparison, in continuous wave regime, of two novel classes of silicon photomultipliers (SiPMs) fabricated on silicon P-type and N-type substrate respectively. Responsivity measurements have been performed with an incident optical power from tenths of picowatts to hundreds of nanowatts and on a broad spectrum, ranging from ultraviolet to near infrared (340-820 nm). For both classes of investigated SiPMs, responsivity shows flat response versus the optical incident power, when a preset overvoltage and wavelength is applied . More in detail, this linear behavior extends up to about 10 nW for lower overvoltages, while a shrink is observed when the reverse b…

Multi-line NIR-RGB emission in Nd:LiNbO3 RPE optical waveguides

Simultaneous generation of four spectral emission lines has been achieved in Nd-doped lithium niobate reverse proton exchange optical waveguide cavities. Using a pump at 800 nm, the four lines were found and they are due to lasing at 1.3735 combined with parametric conversion at 0.687, 0.574 and 0.4 mum.

Ultraviolet quasi-phase-matched second harmonic generation in surface periodically poled lithium niobate optical waveguides

The compatibility of low concentration (alpha-phase) proton exchange channel waveguides with electric field surface periodic poling of congruent lithium niobate (SPPLN) crystals has been experimentally demonstrated. With such waveguides, we obtained ultraviolet second harmonic generation (SHG) by first order quasi-phase-matching (QPM), a result made possible by the fabrication, on Z-cut LN crystals, of periodic structures with a pitch down to 750 nm. Nonlinear copropagating QPM-SHG measurements have been carried out on such structures. The pump source was a Ti:sapphire laser with a tunability range of 700-980 nm and a 40 GHz linewidth. We have measured UV continuous wave light at 390 nm by …

A silicon photomultiplier-based analog front-end for DC component rejection and pulse wave recording in photoplethysmographic applications

The growing attention towards healthcare and the constant technological innovations in the field of semiconductor components have allowed a widespread availability of smaller devices, suitable to be worn and able to continuously acquire physiological signals. Wearable devices are, however, more prone to yield signals corrupted by artifacts caused by movement. This issue is particularly relevant in photoplethysmographic (PPG) applications where also, to exploit the whole dynamic range of the acquisition device, the DC component of the signal should be removed and the AC component amplified. In this context, we have designed and realized an analog front-end (AFE) suitable to be integrated wit…

Design of a portable (CW) fNIRS embedded system

HYDROGELS WITH ORDER POROSITY AT THE MESO-SCALE FOR SENSING

Duplicazione di frequenza e tuning non lineare in guide d’onda in niobato di litio con poling periodico superficiale

Fabrication and Characterization of Dye-Sensitized Solar Cells

Among the next-generation solar cells, a predominant role is played by Dye sensitized solar cells (DSSC) based on ruthenium complexes as sensitizers. They take advantage of a photoelectrochemical system to transform solar radiation into electric energy. In fact, DSSCs represent a cost-effective alternative to traditional silicon-based photovoltaic devices and they do not require expensive and sophisticated apparatus for their fabrication. In this work, we have produced and tested ruthenium DSSCs. In particular, we have measured the main parameters of these cells, such as the electrical and power performances and the efficiency levels, at different irradiance levels and at different incident…

Analysis of Lithium Niobate Surface Layer after Electric Field Periodic Poling and Proton Exchange

Integrated optic surface plasmon resonance measurements in a borosilicate glass substrate

The surface plasmon resonance (SPR) technique is a well-known optical method that can be used to measure the refractive index of organic nano-layers adsorbed on a thin metal film. Although there are many configurations for measuring biomolecular interactions, SPR-based techniques play a central role in many current biosensing experiments, since they are the most suited for sensitive and quantitative kinetic measurements. Here we give some results from the analysis and numerical elaboration of SPR data from integrated optics experiments in a particular borosilicate glass, chosen for its composition offering the rather low refractive index of 1.4701 at 633 nm wavelength. These data regard the…

Surface Plasmon Resonance Optical Biosensors for Mannoproteins Detection

Surface periodic poling in congruent lithium tantalate

Fabrication and electro-optical characterization of Ruthenium-based Dye-Sensitized Solar Cells

In this paper, we measure the main photoelectrical parameters of Dye Sensitized Solar Cells (DSSCs) based on ruthenium complexes at different irradiance levels, incident wavelengths, temperatures and hours of light soaking

CulnSe2/Zn(S,O,OH) junction on Mo foil by electrochemical and chemical route for photovoltaic applications

Electrodeposition is a convenient technique for the development of low cost materials for photovoltaic (PV) device processing. Using a single step electrodeposition route, several groups have fabricated CIS (CuInSe) and CIGS (CuInGaSe) films [1]. One of the most important requirements for successful application of one-step electrodeposition film formation, is the ability to control composition of the deposited films and to develop polycrystalline microstructures with a low surface roughness and high sintered density. In this preliminary work, CIS films were produced by single bath electrodeposition finding the optimal conditions in order to achieve a dense film with high crystallinity and u…

Responsivity measurements of SiC photodiodes

We investigated the technical features of three novel classes of 4H-SiC vertical Schottky UV photodiodes (henceforth, named SiC8, SiC10, SiC20) employing Ni2Si interdigitated strips whose pitch size is 8, 10 and 20 µm respectively [1] and based on the pinch-off surface effect.

Integrated optic Surface Plasmon Resonance Measurements in Glass substrates

The surface plasmon resonance (SPR) technique is an optical method that can be used to measure the refractive index of organic nano-layers adsorbed on a thin metal film. Although there are many techniques for measuring biomolecular interactions, SPR-based techniques play a central role in many current biosensing experiments, since they are most suited to sensitive and quantitative kinetic measurements. Here we give some results from the analysis and numerical elaboration of SPR data regarding the flow of different solutions with refractive indexes in the range of interest (1-1.4). After a brief discussion of the principles of SPR and of waveguide fabrication technique, we give a description…

Characterization of Ruthenium-based Dye-Sensitized solar cells

In this paper, we measure the main photoelectrical parameters of Dye Sensitized Solar Cells (DSSCs) based on ruthenium complexes at different irradiance levels, incident wavelengths, temperatures and hours of light soaking.

Non-uniform doping concentration CIGS absorber profile for highefficiency solar cells

The quaternary chalcopyrite semiconductor alloy Cu(In,Ga)Se2 (CIGS) is nowadays commonly considered one of the most suitable materials to fabricate cost-effective and high-efficiency photovoltaic cells. Thanks to the optical and structural properties of the absorber layer and to the tunable bandgap, thin-film CIGS cells have reached efficiencies around 20%, not far from the maximum values of traditional crystalline silicon cells. This high efficiency, together with the conceivable low fabrication costs, makes CIGS cells a promising alternative to silicon technology for large-scale production. In order to further improve the cells performance, in a previous work we have already proposed a si…

Fabrication and Characterisation of Reverse Proton Exchange Optical Waveguides in Neodymium Doped Lithium Niobate Crystals

In this work, the complete fabrication process which combines Proton Exchange (PE) and Reverse Proton Exchange (RPE) in Neodymium doped LiNbO3 channel waveguides is reported. To produce the PE-RPE channel waveguides the fabrication of dielectric SiO2 masks had to be implemented. For this propose, we adopted a technique based on the Ion Plating Plasma Assisted Deposition of SiO2 followed by the standard ultraviolet photolithographic patterning. On the other hand, we determined the main optical and spectroscopic properties of Nd3+ ions in the channel waveguides including the study of the lifetime as function as the polarisation.

A portable multisensor system to assess cardiorespiratory interactions through photoplethysmography

Nowadays, the ever-growing interest to health and quality of life of individuals and the advancements in electronic devices technology are pushing the development of portable and wearable biomedical devices able to pursue a minimally invasive monitoring of physiological parameters in daily-life conditions. Such devices can now carry out a real-time assessment of the subjects’ overall health status and possibly even detect ongoing diseases. In this context, we have designed and implemented a multisensor portable system able to perform synchronous real-time acquisitions of electrocardiographic (ECG), photoplethysmographic (PPG) and airflow breathing signals. We investigated cardiorespiratory …

Numerical analysis of light soaking phenomenon in Ruthenium based Dye Sensitized Solar Cells

Dye Sensitized Solar Cells (DSSCs) are widely considered one of the most promising third generation photovoltaic devices, especially thanks to their relatively low cost if compared to conventional solar cells. An interesting phenomenon affecting such devices is the so-called light soaking effect, consisting in the increase of cell main electrical parameters after the exposition to solar light. In this work, starting from the experimental characterization carried out on Ruthenium-based DSSCs, we report on a series of numerical analysis performed to better describe the above-mentioned light soaking effect in order to show the relationship between such phenomenon and the main physical paramete…

MATCHING THIN LAYER FOR SURFACE PLASMON RESONANCE TUNING ON LITHIUM NIOBATE WAVEGUIDES

New Cost Effective Titanium Based Protective and Decorative Coatings by Ion Plating Plasma Assisted IPPA

The activity aiming to replace galvanic treatments by vacuum processes is based on the effort to reduce the production costs and to set-up new decorative effects impossible to be galvanically realised because the use of dielectric materials. This work describes cost effective metal-oxide and oxide-metal-oxide decorative coatings based on the use of titanium as basic material deposited by Ion Plating Plasma Assisted from Reactive Magnetron Sputtering source. A new multilayer protective and decorative structure, based on the use of titanium and titanium oxides is also presented. The protective effect against aggressive environment is obtained by alternating layers of metal and metal-oxide mix…

Experimental Investigation on the Performances of Innovative PV Vertical Structures

The sustainable development of our planet is considerably related to a relevant reduction of CO2 global emissions, with building consumption contributing more than 40%. In this scenario, new technological conceptions, such as building-integrated photovoltaic technology, emerged in order to satisfy the requirements of sustainability imposed by the European Union. Therefore, the aim of this work is to provide a technical and economical comparison of the performances of different vertical-mounted innovative photovoltaic systems, potentially integrated on a building instead of on traditional windows or glass walls. The proposed investigation was carried out by means of experimental tests on thr…

Analytical Model for wideband THz sources and detectors based on Optical Rectification and Electro-Optic Sampling

An analytical model describing a laser based set-up for wideband THz generation and detection is presented. Particular attention is focused on the main broadband phenomena, which occur when THz radiations have to be handled.

Surface Plasmon Resonance Measurement of Neutravidin Layer on Gold Thin Film

Signal to noise ratio measurements of silicon photomultipliers in the continuous wave regime

We report on our signal to noise ratio (SNR) measurements carried out, in the continuous wave regime, on a novel class of silicon photomultipliers (SiPMs) fabricated in planar technology on silicon p-type substrate.

Nanopatterned ferroelectric crystals for parametric generation

We report on recent results by surface periodic poling on lithium niobate and lithium tantalate. Such approach allows periodic inversion of the second order susceptibility with nanoscale features using insulating masks. We achieved a world-best 200 nm feature size, as well as good compatibility with alpha-phase proton exchanged channel waveguides in lithium niobate. Preliminary results of surface periodic poling in lithium tantalate also show similar characteristics. Surface poling is best suited for integrated optics devices in technologically-demanding configurations such as backward second harmonic generation and counter propagating optical parametric amplification

Cost Effective Treatments to Replace Galvanic Processes

Some of the most severe problems in the replacement of galvanic treatment with PVD coatings reside, first of all, in the higher costs of vacuum processes and in the difficulty to coat many 3D small samples. This work describes the results obtained by using energetic deposition vacuum processes, of the family of Ion Plating Plasma Assisted (IPPA), using both thermal and sputtering sources, able to reduce dramatically the duration of deposition process and to eliminate the substrate heating and their pre-cleaning. Regarding the small 3D samples, an innovative structure, named "Ionic Rotarybarrel" is presented. The realised treatments are in the fields of decorative, protective and tribologica…

Generazione di seconda armonica nel vicino infrarosso per quasi-accordo di fase in guide a scambio protonico in niobato di litio con polarizzazione periodica superficiale

Ethanol vapor optical sensors based on polystyrene opals infiltrated with hydrogel

Graded Carrier Concentration Absorber Profile for High Efficiency CIGS Solar Cells

We demonstrate an innovative CIGS-based solar cells model with a graded doping concentration absorber profile, capable of achieving high efficiency values. In detail, we start with an in-depth discussion concerning the parametrical study of conventional CIGS solar cells structures. We have used the wxAMPS software in order to numerically simulate cell electrical behaviour. By means of simulations, we have studied the variation of relevant physical and chemical parameters-characteristic of such devices-with changing energy gap and doping density of the absorber layer. Our results show that, in uniform CIGS cell, the efficiency, the open circuit voltage, and short circuit current heavily depe…

Electrochemical and chemical synthesis of CIS/Zn(S,O,OH) for thin film solar cells

In this work, we are reporting results on the electrodeposition of the CuInSe2 thin films on molybdenum thin foil substrates. We have used an aqueous non-buffered electrolyte and a careful choice of deposition parameters to ensure a good quality and composition of the deposited films. In addition, CdS was replaced in the buffer layer with a wider bandgap Zn(S,O,OH) film obtained by chemical bath deposition. The deposited films were annealed in inert atmosphere at different temperatures. The influence of annealing temperature on the properties of the films is briefly discussed. Films were also characterized by photoelectrochemical and I-V measurements. Structural characterization was carried…

PPG/ECG Multisite Combo System Based on SiPM Technology

Two versions of a PPG/ECG combined system have been realized and tested. In a first version a multisite system has been equipped by integrating 3 PPG optodes and 3 ECG leads, whereas in another setup a portable version has been carried out. Both versions have been realized by equipping the optical probes with SiPM detectors. SiPM technology is expected to bring relevant advantages in PPG systems and overcome the limitations of physiological information extracted by state of the art PPG, such as poor sensitivity of detectors used for backscattered light detection and motion artifacts seriously affecting the measurements repeatability and pulse waveform stability. This contribution presents t…

Advanced piezoresistive sensor achieved by amphiphilic nanointerfaces of graphene oxide and biodegradable polymer blends

This work focuses on the preparation of a piezoresistive sensor device, by exploiting an amphiphilic sample of graphene oxide (GO) as a compatibilizer for poly (lactic acid) (PLA)-Poly (ethylene-glycol) (PEG) blends. The presence of GO determined a high stiffening and strengthening effect, without affecting toughness, and allowed a good stability of mechanical properties up to 40 days. Moreover, GO endowed the materials with electrical properties highly sensitive to pressure and strain variations: the biodegradable pressure sensor showed a responsivity of 35 μA/MPa from 0.6 to 8.5 MPa, a responsivity around 19 μA/MPa from 8.5 to 25 MPa. For lower pressure values (around 0.16–0.45 MPa), inst…

Second harmonic generation in coupled LiNbO3 waveguides by reverse-proton exchange

We demonstrate second harmonic generation of a near-infrared pump in a nonlinearly coupled system formed by longitudinally uniform proton- and reverse-proton-exchanged LiNbO/sub 3/ planar waveguides. Phase- and mode-matched transverse electric (TE/sub 0/) frequency doubling into transverse magnetic higher order guided modes is achieved through temperature control, in agreement with the model.

N-on-P and P-on-N Silicon Photomultipliers: Responsivity comparison in the continuous wave regime

We report on the electrical and optical comparison, in continuous wave regime, of two novel classes of silicon photomultipliers fabricated in planar technology on silicon P-type and Ntype substrate respectively. A physical explanation of the experimental results is provided.

Signal to noise ratio measurements of silicon photomultipliers

We report on our signal to noise ratio (SNR) measurements carried out, in the continuous wave regime, on a novel class of silicon photomultipliers (SiPMs) fabricated in planar technology on silicon p-type substrate. SiPMs are large area detectors consisting of a parallel array of Geiger Mode APDs with individual integrated quenching resistors. Each photodiode is an independent photon counting microcell and is connected to a common analog output to produce a summation signal proportional to the number of detected photons [1], [2]. SNR of SiPMs is expressed by the ratio of the SiPM average signal current and the RMS deviation of the overall current (i.e., the overall shot noise current). The …

Responsivity measurements of SiC Schottky photodiodes

We investigated the technical features of three novel classes of 4H-SiC vertical Schottky UV detectors employing Ni2Si interdigitated strips whose pitch size is 8, 10 and 20 µm, respectively, based on the pinch-off surface effect.

Signal to Noise Ratio of Silicon Photomultipliers measured in the Continuous Wave Regime

We performed a Signal to Noise Ratio characterization, in the continuous wave regime, at different bias voltages, frequencies and temperatures, on a novel class of silicon photomultipliers fabricated in planar technology on silicon p-type substrate. Signal to Noise Ratio has been measured as the ratio of the photogenerated current, filtered and averaged by a lock-in amplifier, and the Root Mean Square deviation of the overall current flowing to the device. The measured noise takes into account the shot noise, resulting from the photocurrent and the dark current. We have also performed a comparison between our SiPMs and a photomultiplier tube in terms of Signal to Noise Ratio, as a function …

Statistical analysis of RaptorQ failure probability applied to a data recovery software

In this work, we have implemented a data recovery software integrating the most recent rateless codes, i.e., RaptorQ codes. Thanks to the above-mentioned software, it is possible to recover data loss occurring on several kinds of network conditions. We have performed a statistical analysis of failure probabilities at several configurations of RaptorQ parameters. We have found a good agreement with the theoretical values of a random linear fountain code over Galois Field GF(256). Moreover, we have shown that the probability of having a certain number of failed decoded source blocks - when sending a fixed size file - follows a Poisson distribution.

UV Generation in Surface Periodically Poled Lithium nimbate Proton Exchanged Optical Waveguides

Packet loss recovery in an indoor Free Space Optics link using rateless codes

Free Space Optics (FSO) systems present some important advantages if compared to Radio Frequency links, but they can be affected by several impairments that degrade the link quality and availability. In particular, due to temporary interruptions of the line-of-sight condition between the transmitter and the receiver, packet loss can occur during data transmission. In this work, we present an indoor Free Space Optics link, in which we have systematically generated interruptions of the beam. We demonstrate how the application of the most recent rateless codes, i.e., RaptorQ codes, can strongly improve the link quality by reducing packet loss. In particular, results show that the Packet Error …

Wideband THz time domain spectroscopy based on optical rectification and electro-optic sampling

We present an analytical model describing the full electromagnetic propagation in a THz time-domain spectroscopy (THz-TDS) system, from the THz pulses via Optical Rectification to the detection via Electro Optic-Sampling. While several investigations deal singularly with the many elements that constitute a THz-TDS, in our work we pay particular attention to the modelling of the time-frequency behaviour of all the stages which compose the experimental set-up. Therefore, our model considers the following main aspects: (i) pump beam focusing into the generation crystal; (ii) phase-matching inside both the generation and detection crystals; (iii) chromatic dispersion and absorption inside the c…

Responsivity measurements of silicon carbide Schottky photodiodes in the UV range

We report on the design and the electro-optical characterization of new classes of 4H-SiC Schottky UV detectors, fabricated employing Ni 2 Si interdigitated strips. We have measured, in dark conditions, the forward and reverse I-V characteristics as a function of temperature and C-V characteristics. Responsivity measurements of the devices, as function of wavelength in the UV range, of package temperature and of applied reverse bias are reported. We also compared devices featuring different strip pitch sizes, discussing their performances, and found the device exhibiting best results.

Design and development of a continuous wave functional near infrared spectroscopy system

Functional Near InfraRed Spectroscopy uses light sources and optical detectors for human brain monitoring. In this paper, a portable, low cost, battery-operated, multi-channel, continuous wave fNIRS embedded system, hosting up to 64 LED sources and 128 Silicon PhotoMultiplier optical detectors, is reported on. The designed system is based on a scalable architecture, in which each probe consists of 8 modular and flexible stands, able to host 4 bi-color LEDs as light sources, 16 silicon photomultipliers as photodetectors and a temperature sensor. The hardware structure allows to easily set up several relevant parameters: the timing of the LEDs, the optical power emitted by the LEDs; the acqui…

Optical turbulence measurements and channel modeling of an indoor Free Space Optics link (Abstract)

CIGS PV Module Characteristic Curves Under Chemical Composition and Thickness Variations

This paper analyzes how the electrical characteristics of a CIGS photovoltaic module are affected by the chemical composition and by the thickness variations of the CIGS absorber. The electrical characteristics here considered are the short circuit current, the open circuit voltage, the efficiency and the power peak. The chemical composition is varied by tuning the ratio between gallium and indium. This analysis has been performed by means of the wxAMPS software, developed by the University of Illinois. The above variations have been taken into account on a PV module made of 72 cells. This analysis has been carried out employing a PV module mathematical model developed and implemented by th…

Design and realization of a portable multichannel continuous wave fNIRS

A design and implementation of a portable functional Near InfraRed Spectroscopy embedded system prototype is described. In this theoretical and experimental work, we present an embedded system hosting 64 LED sources and 128 Silicon PhotoMultiplier detectors (SiPM). The elementary part of the structure is a flexible probe “leaf” consisting of 16 SiPMs, 4 couples of LEDs, each operating at two wavelengths, and a temperature sensor. The hardware system is based on an ARM main microcontroller that allows to perform both the switching time of LEDs and the acquisition of the SiPM outputs. The performed preliminary experimental tests achieved very promising results, thus demonstrating the effectiv…

Design and development of a fNIRS system prototype based on SiPM detectors

Functional Near Infrared Spectroscopy (fNIRS) uses near infrared sources and detectors to measure changes in absorption due to neurovascular dynamics in response to brain activation. The use of Silicon Photomultipliers (SiPMs) in a fNIRS system has been estimated potentially able to increase the spatial resolution. Dedicated SiPM sensors have been designed and fabricated by using an optimized process. Electrical and optical characterizations are presented. The design and implementation of a portable fNIRS embedded system, hosting up to 64 IR-LED sources and 128 SiPM sensors, has been carried out. The system has been based on a scalable architecture whose elementary leaf is a flexible board …

Design and implementation of a portable fNIRS embedded system

We report on the design, development and operation of a portable, low cost, battery-operated, multi-channel, functional Near Infrared Spectroscopy embedded system, hosting up to 64 optical sources and 128 Silicon PhotoMultiplier optical detectors. The system is realized as a scalable architecture, whose elementary leaf consists of a probe board provided with 16 SiPMs, 4 couples of bi-color LED, and a temperature sensor, built on a flexible stand. The hardware structure is very versatile because it is possible to handle both the switching time of the LED and the acquisition of the photodetectors, via an ARM based microcontroller.

Progettazione e realizzazione di un sistema Continuous Wave fNIRS basato su tecnologia SiPM

Design of a Multichannel Continuous Wave fNIRS System implemented with SiPM

Performance Investigation of Fountaine Codes on a Simulated Terrestrial Free Space Optical Channel

Analysis of Lithium Niobate Surface after Electric Field Periodic Poling and Proton Exchange

Phosphate ions detection by using an electrochemical sensor based on laser-scribed graphene oxide on paper

In this work, electrodes based on laser-scribed reduced graphene oxide were fabricated using filter paper as the substrate. To fabricate the electrodes, a water suspension of graphene oxide was filtered to produce a continuous and uniform film of graphene oxide on the filter paper surface. Subsequently, a CO2 laser was used to "write" the working, counter and reference eelctroes by reducing graphene oxide in specific areas to define complete sensors. Referecnce electrodes were then coated with a commercial Ag/AgCl conductive paste to produce a quasi Ag/AgCl reference. As fabricated devices were employed as electrochemical sensors for detection of phosphate ions in water by employing the mol…

Low-invasive multisensor real-time acquisition system for the assessment of cardiorespiratory and skin conductance parameters

In recent years, the attention to the health and comfort of the individual, together with the electronic miniaturization progress, have led to an increased interest in the development of biomedical devices that are able to acquire a multitude of biomedical signals. Such devices should be wearable and comfortable during daily use, to be thus suitable for continuously monitoring psychophysical health states. In this context, we have designed and realized a portable biomedical device capable of real-time acquisition of electrocardiographic (ECG), photoplethysmographic (PPG), breathing and galvanic skin response (GSR) signals, for a noninvasive monitoring of multiple physiological parameters. T…

Surface Periodic Poling in Lithium Niobate and Lithium Tantalate

Periodic Poling of Lithium Niobate crystals (PPLN) by means of electric field has revealed the best technique for finely tailoring PPLN structures and parameters, which play a central role in many current researches in the field of nonlinear integrated optics. Besides the most studied technique of bulk poling, recently a novel technique where domain inversion occurs just in a surface layer using photoresist or silica masks has been devised and studied. This surface periodic poling (SPP) approach is best suited when light is confined in a thin surface guiding layer or stripe, as in the case of optical waveguide devices. Also, we found that SPP respect to bulk poling offers two orders of magn…

Low invasive multisensor acquisition system for real-time monitoring of cardiovascular and respiratory parameters

The recent advances in multiparametric monitoring of biosignals and management of big data prompt for the development of devices and techniques for the extraction of indicators with physiological relevance. In this context, we have designed and realized a portable electronic system, equipped with simple biomedical sensors, able to synchronously record multiple electrocardiographic (ECG), photoplethysmographic (PPG) and breathing signals, for carrying out a non-invasive monitoring of several cardiovascular parameters. In this work, we show the results of preliminary measurements performed following a specific physiological protocol (i.e., deep breathing with 10 s per cycle). The system allow…

Responsivity measurements of 4H-SiC Schottky photodiodes for UV light monitoring

We report on the design and the electro-optical characterization of a novel class of 4H-SiC vertical Schottky UV detectors, based on the pinch-off surface effect and obtained employing Ni2Si interdigitated strips. We have measured, in dark conditions, the forward and reverse I–V characteristics as a function of the temperature and the C–V characteristics. Responsivity measurements of the devices, as a function of the wavelength (in the 200 – 400 nm range), of the package temperature and of the applied reverse bias are reported. We compared devices featured by different strip pitch size, and found that the 10 μm device pitch exhibits the best results, being the best compromise in terms of fu…

Comparison on the use of PV systems in the vertical walls

In this article the preliminary evaluation of the performance of a photovoltaic window is presented. The aim is to trace the behavior of next-generation systems, which favor architectonical integration. Three different systems have been taken into account: a dye sensitized solar cell (DSSC), blue and grey caved silicon panels. The systems can be placed behind a window or behind a wall of glass blocks.

Generazione di seconda armonica per quasi accordo di fase in guide a canale su LiNbO3 periodicamente polato in superficie.

Opals infiltrated with a stimuli-responsive hydrogel for ethanol vapor sensing

We report on a novel class of optical materials for ethanol vapor sensing, based on polystyrene opals infiltrated with an innovative stimuli responsive hydrogel. We describe the fabrication process of the bare polystyrene opals and their subsequent infiltration. The optical characterization of the photonic crystal templates was performed to prove the good quality of the samples. Measurements on the infiltrated opals showed that the transmission spectra in the visible range strongly change at varying concentrations of ethanol vapor. The fabricated structures show a linear optical response in the visible range, for high values of ethanol concentration.

Characterization of Thin Film CIG(S,Se)2 submodules using Laser Beam Induced Current Technique

Nowadays, an important class of thin film solar cells consists of CuInGa(S,Se)2 (CIGSSe) solar cells, i.e., composed of Copper, Indium, Gallium, Sulfur and Selenide. Thanks to their electrical and optical properties and to the technological development, thin film integrated photovoltaic modules have nowadays obtained relatively good values of efficiency. In this work, we have performed the electrical and optical characterization of a CIGSSe sub-module by using both a solar simulator equipment and the Laser Beam Induced Current (LBIC) technique.

5th EOS Topical Meeting on Optical Microsystems, Poster OμS13_1569798553: Analytical Model for wideband THz sources and detectors based on Optical Rectification and Electro-Optic Sampling

Brain Monitoring Via an Innovative CW-FNIRS System

Functional Near InfraRed Spectroscopy (fNIRS) is an imaging technique mainly devoted to human brain monitoring. It is used as a non-invasive technique, in medical field, in order to measure the oxygen concentration of blood. This because the relatively good transparency of biological materials in the near infrared allows sufficient photon transmission through tissues. Within the so-called fNIRS range (650-900 nm), the main absorbers are blood chromophores, in particular the oxygenated and deoxygenated haemoglobin (HbO2 and Hb, respectively). When two or more wavelengths are used, changes of such chromophores can be computed by employing the modified Beer-Lambert law, thus providing importan…

Electrical characterization of highefficiency bifacial silicon solar cells

This work presents a preliminary study on the electrical characterization of high efficiency bifacial solar cells. An opening discussion on the state-of-the-art of such advanced technology is initially proposed and the experimental characterization of some prototypes is described. From this analysis, it can be stated that the bifacial silicon solar cells can be a very promising technology with high electrical performances and efficiency.

Parametrical study of multilayer structures for CIGS solar cells

In this paper, a numerical analysis of relevant electrical parameters of multilayer structures for CIGS-based solar cells was carried out, employing the simulation software wxAMPS. In particular, we have focused on thin film cells having a ZnO:Al/ZnO/CdS/CIGS structure with a Molybdenum back contact. The aim of this work is to establish good theoretical reference values for an ongoing experimental activity, where our technology of choice is the single-step electrodeposition. In detail, we have analyzed how the main electrical properties change with the bang gap and the thickness of the absorber layer, for such a type of solar cell structure. Our results show that both efficiency and fill fa…

Responsivity measurements of N-on-P and P-on-N silicon photomultipliers in the continuous wave regime

We report the electrical and optical comparison, in continuous wave regime, of two novel classes of silicon photomultipliers (SiPMs) fabricated in planar technology on silicon P-type and N-type substrate respectively. Responsivity measurements have been performed with an incident optical power from tenths of picowatts to hundreds of nanowatts and on a broad spectrum, ranging from ultraviolet to near infrared (340-820 nm). For both classes of investigated SiPMs, responsivity shows flat response versus the optical incident power, when a preset overvoltage and wavelength is applied . More in detail, this linear behavior extends up to about 10 nW for lower overvoltages, while a shrink is observ…

Anomalous electrical parameters improvement in Ruthenium DSSC

. In this work, we present a series of measurements carried out on Ruthenium-based Dye Sensitized Solar Cells (DSSCs) after the application of different external electrical field values. Such measurements have been performed both in the dark and by illuminating the sample with sunlight emitted by a solar simulator (AM1.5G spectrum with a power irradiance of 1000 W/m2). Our results demonstrate that the initial electrical bias field modifies in both cases the behavior of the cell in terms of an anomalous improvement of the main electrical parameters.

Experimental characterization of Ruthenium-based Dye Sensitized Solar Cells and study of light-soaking effect impact on performance

In this paper, we present an experimental investigation on the performance of Ruthenium-based Dye Sensitized Solar Cells (DSSCs) at different irradiance levels, incident wavelengths and hours of illumination. In particular, the measurements have been aimed at studying the performance variation due to light soaking effect since this phenomenon has noteworthy practical implications, such as stability tests of DSSCs. Our results show that the short circuit current density, the open circuit voltage and the conversion efficiency η increase with the hours of light soaking. Finally, the observed phenomenon is reversible, and thus the performance decreases again when the cell is kept in the dark.

Hydrogel films engineered in a mesoscopically ordered structure and responsive to ethanol vapors

Abstract Responsive hydrogels filling the interstitial spaces of photonic crystals can form mesoscopically structured materials, which exhibit reversible shifts in the Bragg diffracted light as a response of environmental changes. These materials can be used to generate chemical or biochemical sensors. The present work reports on the synthesis and characterization of ethanol responsive hydrogels that can be used in the design of novel breathalyzers. The dynamic mechanical behavior of the macroscopic hydrogels and their swelling features in the presence of different liquids or vapors have been investigated to orientate the choice of the best responsive material and curing process. The swelli…

Electro-Optical characterization of Silicon Carbide Schottky photodiodes

Surface Periodic Domain Engineering in Congruent Lithium Tantalate Crystals

First experiments with the novel electric field Surface Periodic Poling technique have been carried out on Lithium Tantalate. Optimal poling parameters gave 50:50 mark-to-space ratio in the micron scale with good uniformity and high repeatability.

Error mitigation using RaptorQ codes in an experimental indoor free space optical link under the influence of turbulence

In free space optical (FSO) communications, several factors can strongly affect the link quality. Among them, one of the most important impairments that can degrade the FSO link quality and its reliability even under the clear sky conditions consists of optical turbulence. In this work, the authors investigate the generation of both weak and moderate turbulence regimes in an indoor environment to assess the FSO link quality. In particular, they show that, due to the presence of the turbulence, the link experiences both erasure errors and packet losses during transmission, and also compare the experimental statistical distribution of samples with the predicted Gamma Gamma model. Furthermore,…

Ultraviolet quasi-phase-matched second harmonic generation in surface periodically poled Lithium Niobate optical waveguides

Characterization of thin film CIG(S,SE)2 submodules using solar simulator and laser beam induced current techniques (Versione estesa)

In this work, the electrical and optical characterization of CIG(S, Se)2 sub-modules using both a solar simulator equipment and the Laser Beam Induced Current (LBIC) technique is presented. By using the solar simulator and a proper set-up, the electrical parameters of the modules at varying irradiance and temperatures are determined. In addition, the LBIC measurements are carried out to analyze the 2D photocurrent uniformity of the modules at two different wavelengths. Dispersion values of extracted parameters can be very useful for practically tuning the modelling stage at device/module level.

TOTAL INTERNAL REFLECTION ELLIPSOMETRY FOR THE SPECTROSCOPIC INVESTIGATION OF ULTRATHIN SILVER/OXIDE FILMS

Nanotechnology in lithium niobate for integrated optic frequency conversion in the UV

In the domain of Earth Explorer satellites nanoengineered nonlinear crystals can optimize UV tunable solid-state laser converters. Lightweight sources can be based on Lithium Niobate (LN) domain engineering by electric field poling and guided wave interactions. In this Communication we report the preliminary experimental results and the very first demonstration of UltraViolet second-harmonic generation by first-order quasi-phase-matching in a surface-periodically-poled proton-exchanged LN waveguide. The pump source was a Ti-Sapphire laser with a tunability range of 700- 980 nm and a 40 GHz linewidth. We have measured UV continuous-wave light at 390 nm by means of a lock-in amplifier and of …

Nanotecnologie in Niobato di Litio per la conversione di frequenza in ottica integrata nel campo UV.

Optical sensors for ethanol vapor based on polystyrene opals infiltrated with hydrogel

This paper deals with a novel class of optical sensors for ethanol vapor, based on polystyrene opals infiltrated with a hydrogel sensitive to ethanol. Optical characterization of such opals has been performed, proving their effectiveness as sensors

Guided-wave frequency doubling in surface periodically poled lithium niobate: competing effects

We carried out second-harmonic generation in quasi-phase-matched ? -phase lithium niobate channel waveguides realized by proton exchange and surface periodic poling. Owing to a limited ferroelectric domain depth, we could observe the interplay between second-harmonic generation and self-phase modulation due to cascading and cubic effects, resulting in a nonlinear resonance shift. Data reduction allowed us to evaluate both the quadratic nonlinearity in the near infrared as well as the depth of the uninverted domains. © 2007 Optical

A portable electronic system for non-invasive real-time acquisition of multiple physiological signals

In this work, we have designed and realised a portable and compact electronic system for the synchronous acquisition of multiple physiological signals. The system employs a Texas Instruments ADS1298 front-end with 24-bit resolution for data acquisition and supports up to 8 channels and 4 kHz sampling rate. The front-end communicates via SPI with a STM32 microcontroller which pre-processes the data and sends them through USB or Bluetooth to a suitable PC application. The system has been realized for the simultaneous acquisition of electrocardiographic (ECG) and photoplethysmographic (PPG) signals, but it can also be employed for acquiring other typologies of signals, e.g. breathing or electr…

Silicon Photomultipliers Signal-to-Noise Ratio in the Continuous Wave Regime

 Abstract— We report on Signal-to-Noise Ratio measurements carried out, in the continuous wave regime, at different bias voltages, frequencies and temperatures, on a class of silicon photomultipliers fabricated in planar technology on silicon p- type substrate. Signal-to-Noise Ratio has been measured as the ratio of the photogenerated current, filtered and averaged by a lock-in amplifier, and the Root Mean Square deviation of the same current. The measured noise takes into account the shot noise, resulting from the photocurrent and the dark current. We have also performed a comparison between our SiPMs and a photomultiplier tube in terms of Signal-to-Noise Ratio, as a function of the tempe…

Measurements of Silicon Photomultipliers Responsivity in Continuous Wave Regime

We report on the electrical and optical characterization, in continuous wave regime, of a novel class of silicon photomultipliers fabricated in standard planar technology on a silicon p-type substrate. Responsivity measurements, performed with an incident optical power down to tenths of picowatts, at different reverse bias voltages and on a broad (340–820 nm) spectrum, will be shown and discussed. The device temperature was monitored, allowing us to give a physical interpretation of the measurements. The obtained results demonstrate that such novel silicon photomultipliers are suitable as sensitive power meters for low photon fluxes.

Electro-optical characterization of new classes of Silicon Carbide UV photodetectors

In this paper, we present the fabrication process steps and the characterization of 4H-SiC vertical Schottky UV detectors, where interdigitated strips, acting as top metal contacts, have been realized in $\hbox{Ni}_{2}\hbox{Si}$ . These devices exploit the pinch-off surface effect. $I$ – $V$ and $C$ – $V$ characteristics, as functions of temperature, were measured in dark conditions. In addition, we have carried out responsivity measurements, for wavelengths ranging from 200 to 400 nm, at varying package temperature and applied reverse bias. A comparison among devices having different strip pitch sizes has been performed, thus finding out that the 10- $\mu\hbox{m}$ pitch class demonstrates …

Indoor free space optics link under the weak turbulence regime: Measurements and model validation

In this study, the authors present the measurements performed on a free space optics (FSO) communications link using an indoor atmospheric chamber. In particular, the authors have generated several different optical turbulence conditions, demonstrating how even the weak turbulence regime can strongly affect the FSO link performance. The authors have carried out an in-depth analysis of the data collected during the measurements, and calculated the turbulence strength (i.e. scintillation index and Rytov variance) and the important performance metrics (i.e. the Q-factor and bit error rate) to evaluate the FSO link quality. Moreover, the authors have tested, for the first time, an appositely de…

Donor/Acceptor Heterojunction Organic Solar Cells

The operation and the design of organic solar cells with donor/acceptor heterojunction structure and exciton blocking layer is outlined and results of their initial development and assessment are reported. Under halogen lamp illumination with 100 mW/cm2 incident optical power density, the devices exhibits an open circuit voltage VOC = 0.45 V, a short circuit current density JSC between 2 and 2.5 mA/cm2 with a fill factor FF &asymp

Periodically nanostructured hydrogels for ethanol vapors sensing

Chemical sensing using optics has been under extensive research all over the world during last decades and many optical chemical sensors are nowadays finding increasing applications in industry, environmental monitoring, medicine, biomedicine and chemical analysis. These optical sensors can be based on various optical principles, such as absorbance, reflectance or transmittance, luminescence and fluorescence, covering different regions of the spectrum (UV, visible, IR, NIR). Optical chemical sensors have several advantages over conventional electricity-based sensors, in terms of selectivity, immunity to electromagnetic interference, higher sensitivity, and they are also relatively inexpensi…

Moderate-to-Strong Turbulence Generation in a Laboratory Indoor Free Space Optics Link and Error Mitigation via RaptorQ Codes

Free Space Optics (FSO) is rapidly gaining interest as a line-of sight communication technology that offers capabilities similar - in terms of bandwidth and transfer rates - to optical fibre, also possessing several advantages compared with traditional radio frequency links. However, FSO link quality can be strongly affected by unfavourable weather conditions and also by the phenomenon of optical turbulence, even in clear sky. In this work, we have implemented an indoor FSO link and generated moderate-to-strong turbulence conditions along the optical path by using heaters and a mechanical ventilation system. In this way, we have been able to investigate the effects of the generated turbulen…

Electro-optical characterization of highly efficient Dye-Sensitized solar cells

Nowadays, a growing demand for free and clean energy requires the study and the development of new low-cost solar photovoltaic (PV) cells. Among them, Dye Sensitized Solar Cells (DSSCs) based on ruthenium complexes as sensitizers are assuming a great importance. The DSSCs under study are composed placing in succession a transparent conductive glass on which is screen-printed a mesoporous TiO2 thin film sensitized by a ruthenium based dye (N719), an electrolytic solution containing a redox couple (I-/I3-) and another conductive glass covered by a thin transparent catalyst platinum film. In this work, we have measured the main photoelectrochemical parameters of the above mentioned DSSCs at di…

Role of nonlinear absorption during frequency doubling in lithium niobate waveguides.

Progettazione e realizzazione di biosensori a risonanza plasmonica superficiale in ottica integrata.

Cardiovascular parameters detection using a Photoplethismographic system

We propose an innovative, cost-effective and easy to employ photoplethysmographic (PPG) system using Silicon Photomultipliers (SiPMs) sensors to measure cardiovascular parameters that can potentially represent markers for arterial stiffness

Anomalous performance enhancement effects in Ruthenium-based Dye Sensitized Solar Cells

Dye Sensitized Solar Cells (DSSCs) are nowadays more and more employed since they present lower production costs than traditional silicon photovoltaic devices. An interesting phenomenon affecting such devices consists in the fact that current density-voltage (J-V) characteristic can depend on the history of the cell prior to the measurement, which often can be assimilated to an anomalous hysteresis effect. In this work, we study such phenomenon on Ruthenium-based DSSCs through a series of measurements performed after applying different values of external electrical field to the cell. The measurements have been carried out both under simulated sunlight (AM1.5G - 1000 W/m2) and in the dark. W…

Proton exchange channel waveguides compatible with surface domain engineering in Lithium Niobate crystals

First experiments of proton exchange channel waveguides compatible with electric field surface periodic poling of congruent lithium niobate crystals are addressed. Picosecond nonlinear copropagating QPM-SHG measurements have been carried out on such structures.

Generazione di luce UV per interazione QPM/SHG in guida ottica di niobato di litio congruente

Surface periodic poling in congruent lithium tantalate

The first demonstration of surface periodic poling of lithium tantalate at high voltages is reported. Periodic domain inversion with mark-to-space ratios close to the optimum 50:50 was successfully achieved down to micrometre periods with good uniformity and repeatability.

Nanotecnologie SPPLN con maschere in silica e fotoresist

CIGS THIN FILM BY ONE-STEP ELECTRODEPOSITION FOR SOLAR CELLS

In this work, we present a cost-effective technique to produce CIGS thin films for solar cells by means of a single-step electrodeposition. In fact, electrodeposition is known as an easy technique for building low cost materials for photovoltaic device processing. Morphological, structural and optical characterization of these films has been performed.

Variazione della pressione sistolica e diastolica con la respirazione

L’attività di ricerca in corso riguarda la possibilità di ricavare dati clinicamente significativi dai segnali ottici PPG (PhotoPletysmoGraphy). Il segnale PPG viene utilizzato per ricavare informazioni sul volume e sulla saturazione del sangue che interessa il distretto illuminato dalla luce IR (infrarosso) usata per l’analisi. Il volume di sangue contenuto nel segmento di arteria esaminato dipende dalla pressione e dal ciclo cardiaco, attraverso la rigidità dell’arteria.

A prototypal PCB board for the EMI characterization of SiC-based innovative switching devices

In this paper, a preliminary PCB board for the electromagnetic interference (EMI) characterization of innovative silicon-carbide (SiC) based switching devices is presented. Packaging technological issues can determine hurdles in the high-frequency switching and high power regime where wide band gap semiconductors are intended today for Electric Vehicle (EV) applications. In particular, the parasitic inductances that emerge in such devices, must be assessed, by using e.g. EMI techniques. In this specific case, the EMI characterization is supposed to be carried out in a semi-anechoic chamber, available at the University of Palermo (UNIPA), to assess the electromagnetic disturbances according …

Electrical characterization of low power CIGSSe photovoltaic modules

This paper presents the electrical characterization of low power CIGSSe photovoltaic (PV) modules. Such investigation is achieved to perform a comparison of their performances with conventional silicon PV modules. For this purpose, a test bench, suitable for the characterization of both traditional and innovative low power modules, has been set-up and experimental results are accurately described and discussed.

Electro-optical characterization of ruthenium-based dye sensitized solar cells: A study of light soaking, ageing and temperature effects

Abstract In this work, we report on the electro-optical characterization of Dye Sensitized Solar Cells (DSSCs) which use ruthenium complexes as sensitizers. In particular, several kinds of measurements have been performed to study the electrical performances and the efficiency levels of the cells at different operating conditions. In detail, the measurements have been conducted at varying temperatures and hours of light soaking. Our results show that the short circuit current density J SC , the open circuit voltage V OC and the conversion efficiency η increase with the hours of light soaking, while they decrease with temperature. A thorough investigation on the light soaking process at the …

Characterization of Thin Film Cig(S,Se)2 Submodules Using Solar Simulator and Laser Beam Induced Current Techniques

In this work, the electrical and optical characterization of CIG(S,Se)2 sub-modules using both a solar simulator equipment and the Laser Beam Induced Current (LBIC) technique is presented. By using the solar simulator and a proper set-up, the electrical parameters of the modules at varying irradiance and temperatures are determined. In addition, the LBIC measurements are carried out to analyze the 2D photocurrent uniformity of the modules at two different wavelengths. Dispersion values of extracted parameters can be very useful for practically tuning the modelling stage at device/module level.

PV systems in the vertical walls: A comparison of innovative structures

This paper presents the performance comparison of PV windows with the purpose of tracing the behavior of next-generation systems, which could favor architectonical integration. More in detail, a dye sensitized solar cell (DSSC) and blue and grey thin film silicon panels have been analyzed. The systems can be placed behind a window or behind a wall of glass blocks. The three generation systems are then compared in terms of both efficiency and Fill Factor.

Thin Film CIGS Solar Cells, Photovoltaic Modules, and the Problems of Modeling

Starting from the results regarding a nonvacuum technique to fabricate CIGS thin films for solar cells by means of single-step electrodeposition, we focus on the methodological problems of modeling at cell structure and photovoltaic module levels. As a matter of fact, electrodeposition is known as a practical alternative to costly vacuum-based technologies for semiconductor processing in the photovoltaic device sector, but it can lead to quite different structural and electrical properties. For this reason, a greater effort is required to ensure that the perspectives of the electrical engineer and the material scientist are given an opportunity for a closer comparison and a common language.…

Adaptive scheduling of acceleration and gyroscope for motion artifact cancelation in photoplethysmography

Background and objective: Recently, various algorithms have been introduced using wrist-worn photo-plethysmography (PPG) to provide high accuracy of instantaneous heart rate (HR) estimation, including during high-intensity exercise. Most studies focus on using acceleration and/or gyroscope signals for the motion artifact (MA) reference, which attenuates or cancels out noise from the MA-corrupted PPG signals. We aim to open and pave the path to find an appropriate MA reference selection for MA cancelation in PPG.Methods: We investigated how the acceleration and gyroscope reference signals correlate with the MAs of the distorted PPG signals and derived both mathematically and experimentally a…

Light Soaking measurements on Ruthenium-based Dye Sensitized Solar Cells

An interesting phenomenon occurring in Dye Sensitized Solar Cells (DSSCs) when exposed to an uninterrupted period of illumination is the so-called light soaking effect, which consists in the increase of the main electrical parameters of the cell, such as the photocurrent and the efficiency. Studying such an effect has noteworthy practical implications, ranging from the optimization of the manufacturing process to stability tests of DSSCs. In this paper, we present an experimental investigation on the performance variation, due to light soaking, of Ruthenium-based DSSCs.

Continuous Wave fNIRS with Silicon Photomultiplier

This work is focused on the development of a Continuous Wave (CW) NIRS integrated system with multi-wavelength LED sources between 700 and 950 nm and a Silicon Photomultiplier detector (SiPM) developed by STMicroelectronics. The Signal Noise Rate (SNR), measured placing the LEDs and an SiPM in a direct contact with the surface of a plastic phantom mimicking a real human head, results higher than the calculated minimum, required to detect small variation in the HbO2 and HHb concentration, till a source detector separation (SDS) of 6 cm.

Signal to Noise Ratio of Silicon Photomultipliers: a study in the Continuous Wave Regime

We report on Signal to Noise Ratio measurements carried out, in the continuous wave regime, at different bias voltages, frequencies and temperatures, on a novel class of silicon photomultipliers fabricated in planar technology on silicon p-type substrate. Signal to Noise Ratio has been measured as the ratio of the photogenerated current, filtered and averaged by a lock-in amplifier, and the Root Mean Square deviation of the same current. The measured noise takes into account the shot noise, resulting from the photocurrent and the dark current. We have also performed a comparison between our SiPMs and a photomultiplier tube in terms of Signal to Noise Ratio, as a function of the temperature …

CIGS Thin Film by One-Step Electrodeposition Deposition for Solar Cells

Nanotecnologie SPPLN per Dispositivi a Cristalli Fotonici

Photovoltaic module characteristics from CIGS solar cell modelling

We describe our approach to the task of modelling, both at single cell structure and complete module levels, during the solar cell technology development process. This can give very helpful indications, in terms of global photovoltaic module characteristics, for the assessment of intermediate research results and planning of further experiments. We make reference specifically to the fabrication of thin film CIGS solar cells by means of single-step electrodeposition, a technique which appears fairly easy and low-cost but, at the same time, can lead to quite different structural and electrical properties.

SNR measurements of silicon photomultipliers in the continuous wave regime

We report on our Signal-to-Noise Ratio (SNR) measurements carried out, in the continuous wave regime, at different frequencies and at various temperatures, on a novel class of silicon photomultipliers (SiPMs) fabricated in planar technology on silicon p-type substrate. SNR of SiPMs is given by the ratio of the photogenerated current, filtered and averaged by a lock-in amplifier, and the Root Mean Square (RMS) deviation of the same current. In our measurements, we have employed a 10 Hz equivalent noise bandwidth, around the lock-in amplifier reference frequency. The measured noise takes into account the shot noise, resulting from the photocurrent and the dark current, while background light …

Interference-Based Chromatic Coatings by Ion Plating Plasma Assisted Deposition Technology

The goal of replacing widespread and inexpensive galvanic treatments with suitable vacuum deposition techniques, in order to eliminate the environmental hazards and their polluting effects, is becoming, in some cases, more tangible. Shorter cleaning cycles, shorter pump-down times, reduced heating times of substrates and higher deposition rates allow the costs of new plasma-assisted processes to become competitive with respect to galvanic ones. Moreover, vacuum treatments offer superior mechanical and optical properties and non-conductive substrates (like glass, ceramics, plastics) can be more easily coated. This work describes the results obtained with Ion Plating Plasma Assisted depositio…

Poling periodico superficiale in tantalato di litio congruente

CuInSe2/Zn(S,O,OH) junction by electrochemical and chemical route for photovoltaic applications (GE 2014)

Electrodeposition is a convenient technique for the development of low cost materials for photovoltaic (PV) device processing. Using a single step electrodeposition route, several groups have fabricated CIS (CuInSe) and CIGS (CuInGaSe) films. One of the most important requirements for successful application of one-step electrodeposition film formation is the ability to control composition of the deposited films and to develop polycrystalline microstructures with a low surface roughness and high sintered density.

Optical turbulence measurements and channel modeling of an indoor Free Space Optics link

Photonic crystal hydrogel films responsive to ethanol vapors

Simulation analysis of Ruthenium-based Dye Sensitized Solar Cells

Dye Sensitized Solar Cell (DSSC), usually referred as one of the most promising third generation photovoltaic devices, is an electrochemical device in which a molecule (i.e., the dye) chemisorbed onto the surface of a porous material absorbs the incident light and, thus, transfers an electron to the wide band gap semiconductor material. The injected electrons can diffuse through the semiconductor up to the collecting anode without the risk of recombination. The roles of the electrolyte which permeates the cell are to regenerate the ionized molecule and to implement a hole-transporting layer, allowing to repeat the abovementioned process. Thanks to this behaviour, semiconductors with large a…

Employing Microwave Graphene Field Effect Transistors for Infrared Radiation Detection

In this work, we investigate the possibility of employing graphene field effect transistors, specifically designed for microwave applications, as infrared detectors for telecom applications. Our devices have been fabricated on a sapphire substrate employing CVD-grown transferred graphene. The roles of both the gate dielectric and the DC bias conditions have been evaluated in order to maximize the infrared generated signal through an experimental investigation of the signal-to-noise ratio dependence on the transistor operating point.

Ostruzione polmonare ed aritmia respiratoria

Il monitoraggio di pazienti tramite segnali fotopletismografici (PhotoPlethysmoGram, PPG) acquisiti sul polso, arteria radiale, piuttosto che sulla punta dell’indice, permette di ottenere un segnale più stabile e con maggiori informazioni, come la gittata cardiaca, la durata della contrazione ventricolare e la chiusura dell’aorta. In questo lavoro è presentata un’attività preliminare per rilevare condizioni come l’ostruzione polmonare e le apnee notturne. Si è indagato l’andamento dell’aritmia respiratoria in relazione ad eventuali difficoltà respiratorie. Per il momento ci si è limitati ad osservare soggetti sani e l’ostruzione è stata simulata facendo respirare i soggetti attraverso una c…

Development of a CW-fNIRS System for brain monitoring

A portable system for multiple parameters monitoring: towards assessment of health conditions and stress level in the automotive field

In this work, an electronic portable combo system able to synchronously acquire multiple signals, e.g. electrocardiographic (ECG), photoplethysmographic (PPG) and breathing waveforms, is presented. The realized system is also capable of showing in real time some physiological parameters which can be used for assessing health/stress status of the volunteer, such as heart rate and breathing frequency and their trends over time. Thanks to the use of non-invasive PPG probes, of batteries as power supply, and to the possibility to add in the future additional sensors to acquire other signals, the system could also be employed inside vehicles for assessing the status of the driver. Finally, the r…

Physiological parameters measurements in a cardiac cycle via a combo PPG-ECG system

In this paper, we present an innovative way to measure some physiological parameters (such as the pre-ejection period, the pulse transit time, the blood pressure) in a cardiac cycle. A combo PPG-ECG system has been developed and employed to extract both the ECG signal from standard limb leads and simultaneously the photoplethysmography signal from the wrist and the forearm, to calculate the pre-ejection period. This system represents an easy and non-invasive technique to determine these biomedical parameters without using expensive impedance cardiography equipment.

Guide d’onda a scambio protonico in cristalli ferroelettrici con domini ingegnerizzati superficialmente

Blood Pressure Monitoring with a PPG Embedded System

Frequency doubling in surface periodically poled lithium niobate waveguides: Competing effects

We fabricated α-phase pro ton-exchanged (PE) lithium niobate (LN) channel waveguides quasi phase-matched (QPM) via surface periodic poling (SPP) and carried out the first experimental demonstration of second harmonic generation (SHG) in such devices.[1] Experiments were performed by employing an optical parametric amplifier/oscillator producing 25 ps pulses in the range 1.1-1.6 μm with a line-width less than 2cm−1 and a repetition rate of 10Hz. SHG measurements were performed either at a fixed wavelength by varying the fundamental frequency (FF) input power or by scanning the FF wavelength, ratioing the second harmonic (SH) output to the FF input to obtain the conversion efficiency. By repe…

P-on-N and N-on-P silicon photomultipliers: an in-depth analysis in the continuous wave regime

We report on the electrical and optical comparison, in the continuous wave regime, of two novel classes of silicon photomultipliers fabricated in planar technology on silicon P-type (N-on-P class) and N-type (P-on-N class) substrates respectively.

Laser Beam Induced Current measurements on Dye Sensitized Solar Cells and thin film CIG(S,SE)<inf>2</inf> modules

Calculating the efficiency of a solar cell depends on a precise knowledge of its area. Indeed, the photoresponse uniformity is essential to improve the manufacturing process. In this work we report on Laser Beam Induced Current measurements performed on CIG(S,Se) 2 modules and Dye Sensitized Solar Cells. These measurements, performed via a green and a red HeNe lasers both operating at an optical irradiance of 1 Sun, allowed to obtain an accurate photoresponse map of the specimens and highlighted the non-uniformities with a spatial resolution of 400 µm and 80 µm, respectively.

Optical turbulence measurements and channel modeling of an indoor Free Space Optics link (Versione estesa)

In this work, we propose an indoor experimental set-up able to generate several optical turbulence conditions in a Free Space Optics link. Using this set-up, we prove the effectiveness of an irradiance time-series generator based on the Gamma-Gamma model and able to predict the irradiance fluctuations at the receiver, under both weak and moderate turbulence conditions.

Wearable Multisensor Ring-Shaped Probe for Assessing Stress and Blood Oxygenation: Design and Preliminary Measurements

The increasing interest in innovative solutions for health and physiological monitoring has recently fostered the development of smaller biomedical devices. These devices are capable of recording an increasingly large number of biosignals simultaneously, while maximizing the user’s comfort. In this study, we have designed and realized a novel wearable multisensor ring-shaped probe that enables synchronous, real-time acquisition of photoplethysmographic (PPG) and galvanic skin response (GSR) signals. The device integrates both the PPG and GSR sensors onto a single probe that can be easily placed on the finger, thereby minimizing the device footprint and overall size. The system enables the e…

Nonstoichiometric silica mask to fabricate reverse proton-exchange waveguides in lithium niobate crystals

Producing channel waveguides requires a photolithographic mask, but the standard technique of using thermally evaporated metal films for proton exchange has proved to be unsuitable for withstanding the rather aggressive process of reverse proton exchange. We report the fabrication of a nonstoichiometric silica mask by ion-plating plasma-assisted deposition. This mask is strong enough to resist both direct and reverse proton exchange and is also compatible with anisotropic dry etching for patterning the mask and with electric field poling. Our technique is a practical alternative to the use of SiO2 sputtered masks.