Search

Fiber optic sensors have become increasingly well-established due to the many advantages they provide such as immunity to electromagnetic interference, multiplexing capabilities, and remote sensing. The coupling of light with a transducer at the tip of the optical fiber enables the detection of physical and biological parameters. 2D photonic crystals (PhC) can be designed to feature guided-mode resonances (GMR) characterized by a strong electric field at the PhC surface, providing a suitable tool for the detection of local refractive index variations (e.g. biomolecule adsorption). Here, we demonstrate the use of a PhC transferred to the tip of a single-mode fiber for biosensing. The control of surface chemistry provides a sensitive platform for the molecular recognition of antibody biomarkers. By integrating the fiber in a continuous flow platform, the real-time detection of anti-IgG in undiluted serum was achieved, with a limit of detection down to 60 pM. Moreover, the use of a reference channel is demonstrated to correct for signal drifts in real-time due to changes in bulk refractive index. These referenced fiber-tip PhC biosensors may pave the way for fluidic integrated systems in environmental, industrial, and healthcare applications, and open up the possibility of biosensing in the human body by integrating them into catheters.

To facilitate convenient packaging of photonic integrated circuits on a fiber tip, a silicon grating coupler designed for vertical backside coupling has been developed. In order to comply with foundry capabilities and streamline the fabrication processes, the grating coupler features a minimum feature size larger than 200 nm and a single-etched structure on silicon. By inverse design-based optimization, the vertical backside grating coupler achieves a coupling efficiency of nearly 40% (−3.97 dB), while showcasing high fabrication and misalignment tolerance.

This article constitutes a theoretical reflection from an educational perspective that places emphasis on the notion of inhabiting in the present technological society. The discussion is based on John Dewey's pragmatism, particularly on the idea of ​​technology resulting from the fundamental tenets of his conception of experience and aesthetics. A key element is the notion of habit, through which we manage our relationship with reality or inhabit it. Starting from an examination of technology in relation to the Deweyan notion of experience, the discussion moves towards the importance of the aesthetic dimension to come, finally, to some considerations on the meaning of habits in education and human existence.

Spectral sensing is an emerging field driven by the need for fast and non-invasive methods for the chemical analysis of materials in agri-food, healthcare, and industrial applications. We demonstrate a near-infrared spectral sensor, based on a scalable fabrication process and combining high responsivity, narrow linewidth, and low noise. The sensor consists of 16 resonant-cavity-enhanced photodetectors, each showing a unique spectral response consisting of narrow peaks. The spectral sensor thereby covers the wavelength range between 890 and 1650 nm, where organic materials show relevant spectral features from first and second overtones. For the fabrication of the detector arrays, we propose a simple and scalable fabrication approach that yields largely improved device characteristics with respect to the grey-scale electron-beam lithography process reported earlier. Through a series of five optical lithography steps, tuning layers of silicon nitride are deposited stepwise to obtain 16 different thicknesses and reduced surface roughness. With this novel fabrication approach, the obtained photodetectors achieve an average peak linewidth of 55 nm, a maximum peak responsivity of 0.3 A/W, and high suppression of the non-resonant background. We also demonstrate the impact of these improvements on the sensing performance for two relevant problems through an experiment and a set of simulations. With lateral dimensions of ∼1.4 × 1.4 mm2, the proposed photodetector array can be the key to robust, portable, and low-cost sensing instrumentation for on-site material analysis in various application fields.

What are the minimal hardware requirements for a given class of sensing problems? Here, authors investigate this while proposing a miniaturized near-infrared spectral sensor, based on an array of resonant-cavity enhanced photodetectors, and capable of operating without the need for spectral reconstruction.

This paper aims to analyse the notion of familiarity in Dewey’s pragmatism in order to show its important role as a tool for human beings to interpret the reality, manage it, and act within it. Starting from an examination of Deweyan transactional realism, the discourse focuses on familiarity and its related terms (such as “familiar,” “to familiarize,” but also opposites such as “unknown” or “strange”) in Dewey’s thought, to finally come to highlight its fundamental hermeneutic role. This might be useful to account for a subject of Deweyan thought not so deeply highlighted by scholarship and, at the same time, to show pragmatism’s closeness to hermeneutics regarding the relation between the human being and the real.

We demonstrate fiber optic sensors with temperature compensation for the accurate measurement of ethanol concentration in aqueous solutions. The device consists of two photonic crystal (PhC) fiber-tip sensors: one measures the ethanol concentration via refractive index (RI) changes and the other one is isolated from the liquid for the independent measurement of temperature. The probes utilize an optimized PhC design providing a Lorentzian-like, polarization-independent response, enabling a very low imprecision (pm-level) in the wavelength determination. By combining the information from the two probes, it is possible to compensate for the effect that the temperature has on the concentration measurement, obtaining more accurate estimations of the ethanol concentration in a broad range of temperatures. We demonstrate the simultaneous and single-point measurements of temperature and ethanol concentration in water, with sensitivities of 19 pm/°C and ∼53 pm/%, in the ranges of 25 °C to 55 °C and 0 to 50% (at 25 °C), respectively. Moreover, a maximum error of 1.1% in the concentration measurement, with a standard deviation of ≤0.8%, was obtained in the entire temperature range after compensating for the effect of temperature. A limit of detection as low as 0.08% was demonstrated for the concentration measurement in temperature-stable conditions.

On-chip mechanical sensing platforms require tuneable lasers with narrow linewidth and low spectral noise, making read-out challenging. Here, the authors report a nanomechanical sensor with 80nm bandwidth, displacement imprecision of 45 fm/Hz1/2 as well as a dynamic range greater than 30 nm with integrated photodetectors.

For decades, near-infrared (NIR) spectroscopy has been a valuable tool for material analysis in a variety of applications, ranging from industrial process monitoring to quality assessment. Traditional spectrometers are typically bulky, fragile and expensive, which makes them unsuitable for portable and in-field use. Thus, there is a growing interest for miniaturized, robust and low-cost NIR sensors. In this study, we demonstrate a handheld NIR spectral sensor module, based on a fully-integrated multipixel detector array, sensitive in the 850–1700 nm wavelength range. Differently from a spectrometer, the spectral sensor measures a limited number of NIR spectral bands. The capabilities of the spectral sensor module were evaluated alongside a commercially available portable spectrometer for two application cases: to quantify the moisture content in rice grains and to classify plastic types. Both devices achieved the two sensing tasks with comparable performance. Moisture quantification was achieved with a root mean square error (RMSE) prediction of 1.4% and 1.1% by the spectral sensor and spectrometer, respectively. Classification of the plastic type was achieved with a prediction accuracy on unknown samples of 100% and 96.4% by the spectral sensor and spectrometer, respectively. The results from this study are promising and demonstrate the potential for the compact NIR modules to be used in a variety of NIR sensing applications.

Due to their small sizes and low threshold, nanolasers play a pivotal role in the field of low-energy scalable photonic technologies. High-speed modulation of nanolasers is needed for their application in data communication, but its implementation has been hampered by the small scales involved, leading to large electrical parasitics. Here we experimentally demonstrate the proof-of-principle of a novel modulation technique, namely, mode-field switching, which unlocks the control of the laser operation via the modulation of the electromagnetic field. In particular, we show that stimulated emission can be inhibited by switching the lasing mode from bright to dark in a three-coupled cavity system. The experimental results are in good agreement with a model that combines coupled-mode theory and rate equations. Using this model, we show that time-dependent detuning schemes enable storage and release of energy under the form of short pulses, placing mode-field switching among the techniques for laser modulation and pulse generation. This scheme is general and can be implemented in every platform displaying coupled and tuneable resonances.

Fano lineshapes are found in many photonic systems where discrete and extended spectra interfere. Here, the authors extend this description and introduce generalized Fano lineshapes to describe the results from hyperspectral mapping around an exceptional point in a coupled-cavity system.

Fully integratable spectrometers have trade-offs between size and resolution. Here, the authors present a nano-opto-electro-mechanical system where the functionalities of transduction, actuation and detection are fully integrated, resulting in an ultra-compact high-resolution spectrometer with a micrometer-scale footprint.

An amendment to this paper has been published and can be accessed via a link at the top of the paper.

Quantum photonic integrated circuits (QPICs) on a GaAs platform allow the generation, manipulation, routing, and detection of non-classical states of light, which could pave the way for quantum information processing based on photons. In this article, the prototype of a multi-functional QPIC is presented together with our recent achievements in terms of nanofabrication and integration of each component of the circuit. Photons are generated by excited InAs quantum dots (QDs) and routed through ridge waveguides towards photonic crystal cavities acting as filters. The filters with a transmission of 20% and free spectral range ≥66 nm are able to select a single excitonic line out of the complex emission spectra of the QDs. The QD luminescence can be measured by on-chip superconducting single photon detectors made of niobium nitride (NbN) nanowires patterned on top of a suspended nanobeam, reaching a device quantum efficiency up to 28%. Moreover, two electrically independent detectors are integrated on top of the same nanobeam, resulting in a very compact autocorrelator for on-chip g(2)(τ) measurements.

In this paper, Andrea Fiore sketches the notion of familiarity in Dewey's thought, particularly in its relations with education, aesthetics, and art. The importance of that notion emerges in Dewey's well-known writings such as "How We Think," "The School and Society," and "Art as Experience," where he shows that not only does familiarity play a fundamental role in our lives, but it also constitutes a helpful tool to make our experience deeper and richer. This is particularly evident in two aspects or functions related to familiarity: recognition and interpretation. For Dewey, especially the latter has an educational value through aesthetics and art, because it allows us to activate the peculiar capacity of human beings to transform the quality of experience.

Abstract The application of a periodic nonresonant drive to a system allows the Floquet engineering of effective fields described by a broad class of quantum simulated Hamiltonians. The Floquet evolution is based on two different elements. The first one is a time-independent or stroboscopic evolution with an effective Hamiltonian corresponding to the quantum simulation target. The second element is the time evolution at the frequencies of the nonresonant driving and of its harmonics, denoted as micromotion. We examine experimentally and theoretically the harmonic dual-dressing Floquet engineering of a cold atomic two-level sample. Our focus is the dressing operation with small bare energies and large Rabi frequencies, where frequencies and amplitudes of the stroboscopic/micromotion time evolutions are comparable. At the kHz range of our dressed atom oscillations, we probe directly both the stroboscopic and micromotion components of the qubit global time evolution. We develop ad-hoc monitoring tools of the Floquet space evolution. The direct record of the time evolution following a pulsed excitation demonstrates the interplay between the two components of the spin precession in the Floquet space. From the resonant pumping of the dressed system at its evolution frequencies, Floquet eigenenergy spectra up to the fifth order harmonic of the dressing frequency are precisely measured as function of dressing parameters. Dirac points of the Floquet eigenenergies are identified and, correspondingly, a jump in the dynamical phase shift is measured. The stroboscopic Hamiltonian eigenfrequencies are measured also from the probe of the micromotion sidebands.These monitoring tools are appropriate for quantum simulation/computation investigations. Our results evidence that the stroboscopic phase shift of the qubit wavefunction contains an additional information that opens new simulation directions.

Abstract Liver transplant (LT) recipients are vulnerable to SARS-CoV-2-infection (COVID-19), due to immunosuppression and comorbidities. This study aimed to evaluate the impact of COVID-19 on LT recipients compared to general population in the Campania region. In this prospective double-centre study, we enrolled all consecutive adult LT recipients with confirmed SARS-CoV-2-infection. Data were collected at diagnosis of COVID-19 and during follow-up and compared with the regional population. Thirty LT recipients (3.28%) developed SARS-CoV-2-infection (76.66% male, median age 62.61 years). Sixteen (53.33%) were symptomatic. Common symptoms were fever, cough, fatigue, and anosmia. Twenty-five (83.33%) were outpatients, 5 (16.66%) required hospitalization (6.66% admitted to Intensive Care Unit, 6.62% developed Acute Respiratory Distress Syndrome and 6.66% died). Immunosuppressors were in 3 (10%) patients. Incidence rate of COVID-19 was similar between LT patients and general population (3.28% vs 4.37%, p = 0.142) with higher rate of symptoms in LT patients (53.33% vs 15.87%, p

Background: In more than 90% of chronic viral hepatitis C (HCV) patients treated with direct-acting antiviral agents (DAAs), a sustained viral response (SVR) was observed. Unfortunately, there are subgroups of subjects who display enduring liver fibrosis and are at high risk of developing hepatocellular carcinoma (HCC). Thus, liver fibrosis evaluation during the follow-up of these patients plays a pivotal role. The gold standard to evaluate hepatic fibrosis is liver biopsy, which is an invasive procedure. Imaging techniques and serum biomarkers have been proposed as safer and cheaper procedures.Objectives: In this study, we evaluated the concordance of transient elastography (TE) with ELF score ( enhanced liver fibrosis) in a cohort of patients with HCV before and after direct-acting antiviral (DAAs) treatment. ELF score has been validated in other chronic liver diseases; the evidence is not available in HCV patients treated with DAAs.Study design: We prospectively recruited all consecutive HCV patient candidates for DAAs therapy at the University of Naples “Federico II” between April 2015 and July 2016. TE and ELF scores were assessed at baseline, at SVR24, and at SVR48.Results: One-hundred-nineteen patients were treated with DAAs, and 94.1% of them reached SVR. A total of 55.5% of patients were males with a mean age of 64.7 ± 9.6 years. TE results revealed that 12 patients (10%) had F1-2 mild/moderate fibrosis, and 107 (90%) had F3-4 advanced fibrosis. At baseline, SVR24, and SVR48, the concordance between ELF test and TE was poor: 0.11 (p = 0.086), 0.15 (p = 0.124), and 0.034 (p = 0.002), respectively. However, at SVR24 and SVR48, both methods showed a significant amelioration of liver fibrosis compared to baseline (p < 0.001). In addition, both ELF index and TE were significantly associated with portal hypertension at baseline, but not with varices and ascites.Conclusions: Our findings suggested that ELF test could predict changes in liver fibrosis, independently of TE. In case of TE unavailability, ELF score could represent an appropriate tool. Notably, in the context of the COVID-19 pandemic, ELF testing should be encouraged to reduce unnecessary access to the hospital and prolonged physical contact.

Thyroid hormones have a considerable influence on cardiac function and structure. There are direct and indirect effects of thyroid hormone on the cardiovascular system, which are prominent in both hypothyroidism and hyperthyroidism. In this review, we discuss how thyroid dysfunction impacts cardiovascular pathophysiology and the underlying molecular mechanisms.

Background: Low flow (LF) in heart failure with preserved ejection fraction (HFpEF) is a paradox but is associated with worse prognosis. Determinants of LF in HFpEF have not been clarified but their assessment could corroborate recognition and definition of such a paradoxical condition. Methods: A cohort of 193 patients hospitalized with HFpEF was retrospectively studied and divided in a group with LF (N = 45), defined by a left ventricular (LV) stroke volume index (SVI)

Supersolids are a fundamental quantum phase of matter where the global phase and translational symmetries are spontaneously broken. The recently discovered supersolidity in quantum gases of strongly magnetic atoms gives the opportunity to explore in depth how superfluidity and crystalline order are mixed in this fascinating phase. The dipolar supersolid is usually created from a Bose-Einstein condensate, i.e., a standard superfluid, crossing a quantum phase transition that is related to the crystallization transitions of ordinary matter. In this work, we assess experimentally and theoretically the character of the superfluid-supersolid quantum phase transition. We find that one-row supersolids can have already two types of phase transitions, discontinuous and continuous, that are reminiscent of the first- and second-order transitions predicted in the thermodynamic limit in 2D and 1D, respectively. The dimensional crossover is peculiar to supersolids, is controlled via the transverse confinement and the atom number, and can be justified on the general ground of the Landau theory of phase transitions. The quasiadiabatic crossing of a continuous phase transition opens new directions of investigation for supersolids.

PurposeCardiac involvement in Systemic Sclerosis (SSc) is increasingly recognized as a mayor cause of morbidity and mortality. The aim of present study is to investigate the early stages of cardiac involvement in SSc by Cardiovascular magnetic resonance (CMR), combining the non-invasive detection of myocardial inflammation and fibrosis using T2 and T1 mapping techniques and the assessment of microcirculatory impairment through perfusion response to cold pressor test (CPT).Methods40 SSc patients (30 females, mean age: 42.1 years) without cardiac symptoms and 10 controls underwent CMR at 1.5 T unit. CMR protocol included: native and contrast-enhanced T1 mapping, T2 mapping, T2-weighted, cineMR and late gadolinium enhancement (LGE) imaging. Microvascular function was evaluated by comparing myocardial blood flow (MBF) on perfusion imaging acquired at rest and after CPT. Native myocardial T1 and T2 relaxation times, extracellular volume fraction (ECV), T2 signal intensity ratio, biventricular volumes and LGE were assessed in each patient.ResultsSSc patients had significantly higher mean myocardial T1 (1029±32ms vs. 985±18ms, pConclusionsMyocardial involvement in SSc at preclinical stage increases native T1, T2 and ECV values, reflecting inflammation and fibrosis, and reduces vasodilatory response to CPT, as expression of microvascular dysfunction.

A 75-year-old female underwent a High Resolution Computed Tomography (HRCT) scan for recurrent bronchitis and cough. HRCT images showed an anomalous supernumerary bronchus to the right upper lobe directly arising from the right side of distal trachea, corresponding to Tracheal Bronchus (TrB). TrB can cause recurrent right upper lobe pneumonia and special care is requiring during endotracheal intubation.

We report a systematic study of the In-assisted deoxidation (IAD) of epitaxial GaAs(100) substrates. Optimized IAD conditions resulting in a pit-free and smooth GaAs surface are found. Photoluminescence lines from single quantum dots (QDs) with linewidths in the range of 250–400 μeV are observed from low-density InAs QDs grown at a distance of 10 nm from a GaAs surface deoxidized under an optimized condition. Our study shows that IAD is very promising for application in the growth of nanostructures on patterned GaAs substrates. [ABSTRACT FROM AUTHOR]

In recent years, photon-number-resolving (PNR) detectors have attracted great interest, mainly because they can play a key role in diverse application fields. A PNR detector with a large dynamic range would represent an ideal photon detector, bringing the linear response of conventional analogue detectors down to the single-photon level. Several technologies, such as InGaAs single photon avalanche detectors (SPADs), arrays of silicon photomultipliers, InGaAs SPADs with self-differencing circuits and transition edge sensors have shown photon number resolving capability. Superconducting nanowires provide free-running single-photon sensitivity from visible to mid-infrared frequencies, low dark counts, excellent timing resolution (<60 ps) and short dead time (∼10 ns), at an easily accessible temperature (2–3 K), but they do not inherently resolve the photon number. In this framework, PNR detectors based on arrays of superconducting nanowires have been proposed. In this article we describe a number of methods and device configurations that have been pursued to obtain PNR capability using superconducting nanowire detectors. [ABSTRACT FROM AUTHOR]

We report a systematic study of the In-assisted deoxidation (IAD) of epitaxial GaAs(100) substrates. Optimized IAD conditions resulting in a pit-free and smooth GaAs surface are found. Photoluminescence lines from single quantum dots (QDs) with linewidths in the range of 250–400 μeV are observed from low-density InAs QDs grown at a distance of 10 nm from a GaAs surface deoxidized under an optimized condition. Our study shows that IAD is very promising for application in the growth of nanostructures on patterned GaAs substrates. [ABSTRACT FROM AUTHOR]

A very promising way to increase the detection efficiency of nanowire superconducting single-photon detectors (SSPDs) consists in integrating them with advanced optical structures such as distributed Bragg reflectors (DBRs) and optical waveguides. This requires transferring the challenging SSPD technology from the usual substrates, i.e. sapphire and MgO, to an optical substrate like GaAs, on which DBRs and waveguides can be easily obtained. Therefore, we optimized the deposition process of few-nm thick superconducting NbN films on GaAs and AlAs/GaAs-based DBRs at low temperatures (substrate temperature TS = 400 degC), in order to prevent As evaporation. NbN films ranging from 150 to 3 nm in thickness were then deposited on single-crystal MgO, GaAs, MgO-buffered GaAs and DBRs by current-controlled DC magnetron sputtering (planar, circular, balanced configuration) of Nb in an Ar+N2 plasma. 5.5 nm thick NbN films on GaAs exhibit TC = 10.7 K, DTC = 1.1 K and RRR = 0.7. The growth of such high quality thin NbN films on GaAs and DBRs has never been reported before. [ABSTRACT FROM AUTHOR]

We demonstrate a novel method to measure Nth-order (N=1,2,3,4) interferometric autocorrelation with high sensitivity and temporal resolution. It is based on the combination of linear absorption and nonlinear detection in a superconducting nanodetector, providing much higher efficiency than methods based on all-optical nonlinearities. Its temporal resolution is only limited by the quasiparticle energy relaxation time, which is directly measured to be in the 20 ps range for the NbN films used in this work. We present a general model of interferometric autocorrelation with these nonlinear detectors and discuss the comparison with other approaches and possible improvements. [ABSTRACT FROM AUTHOR]