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Low-dimensional nanostructures, especially one-dimensional materials, exhibit remarkable anisotropic characteristics due to their low symmetry, making them promising candidates for polarization-sensitive photodetection. Here, we present a chemical vapor deposition synthesis method for tellurium suboxide (TeOx), confirming the practicality of photodetectors constructed from TeOx nanowires (NWs) in high-responsivity, broadband, and polarization-sensitive detection. By precisely controlling the thermodynamics and kinetics of TeOx NWs growth, we achieve large-scale growth of TeOx NWs with highly controllable dimensions and propose a method to induce intrinsic built-in strain in TeOx NWs. Photodetectors based on quasi-one-dimensional TeOx NWs with ohmic contact demonstrate broadband spectral response (638–1550 nm), high responsivity (13 700 mA·W−1), and superior air stability. Particularly, owing to the inherent structural anisotropy of the photodetectors, they exhibit polarization-sensitive photodetection, with anisotropy ratios of 1.70 and 1.71 at 638 and 808 nm, respectively. [ABSTRACT FROM AUTHOR]

The temperature dependence of spectra can reveal important insights into the structural and dynamical behavior of the system being probed. In the case of linear spectra, this has been exploited to investigate the thermodynamic driving forces governing the spectral response. Indeed, the temperature derivative of a spectrum can be used to obtain effective energetic and entropic profiles as a function of the measured frequency. The former can further be used to predict the temperature-dependent spectrum via a van't Hoff relation. However, these approaches are not directly applicable to nonlinear, complex-valued spectra, such as vibrational sum-frequency generation (SFG) or two-dimensional infrared (2D-IR) photon echo spectra. Here, we show how the energetic and entropic driving forces governing such nonlinear spectra can be determined and used within a generalized van't Hoff relation to predict their temperature dependence. The central idea is to allow the underlying energetic profiles to themselves be complex-valued. We illustrate this approach for 2D-IR spectra of water and SFG spectra of the air–water interface and demonstrate the accuracy of the generalized van't Hoff relationship and its implications for the origin of temperature-dependent spectral changes. [ABSTRACT FROM AUTHOR]

Solution-processed organic photodetectors (OPDs) with spectral response in the near-infrared (NIR) region have broad applications such as in industries, spectroscopic/medical instruments, communications, image sensing, and environmental monitoring. OPDs capable of selective spectral response are particularly appealing for applications including secure optical data link and color image sensing systems. Here, we report an organic photodetector with a highly selective spectral response to near-infrared radiation without the use of a color filter. The operation of the OPDs takes advantage of a charge collection narrowing effect, resulting in a narrowband response at 760 nm with a full width at half maximum of 47 nm and an external quantum efficiency of 46%. Owing to the features of the narrowband response in NIR, our organic photodetectors are used as optical signal receivers for an optical communication system, which achieves a data transmission rate of 12.6 kB/s with a low bit error rate on the order of 10−4. We further investigated the response bandwidth in devices with different active layer thicknesses and area size and their response bandwidth under different reverse bias conditions as well. The optimized device shows a −3 dB response bandwidth of 3.02 MHz and a data transmission rate of 1.41 Mbit/s. The results highlight the promising potential of the nonfiltered OPDs for a variety of applications, including light communication, short-range data transmission, and image sensing. [ABSTRACT FROM AUTHOR]

We present new results on the underlying guest–host interactions and spectral characterization of a CO2 molecule confined in the cages of the sI clathrate hydrate. Such types of porous solids raise computational challenges, as they are of practical interest as gas storage/capture materials. Accordingly, we have directed our efforts toward addressing their modeling in a proper manner, ensuring the quality of the input data and the efficiency of the computational approaches. The computational procedure for spectral simulations, within the multi-configurational time-dependent Hartree framework, involves the development of a fully coupled Hamiltonian, including an exact kinetic energy operator and a many-body representation of the potential, along with dipole moment surfaces, both obtained through neural network machine learning techniques. The resulting models were automatically trained and tested on extensive datasets generated by PW86PBE-XDM calculations, following the outcome of previous benchmark studies. Our simulations enable us to explore various aspects of the quantized dynamics upon confinement of CO2@D/T, such as constrained rotational–translational quantum motions and the averaged position/orientation of the CO2 guest in comparison to the experimental data available. Particularly notable are the distinct energy patterns observed in the computed spectra for the confined CO2 in the D and T cages, with a considerably high rotational–translational coupling in the CO2@T case. Leveraging reliable computations has proved instrumental, highlighting the sensitivity of the spectral features to the shape and strength of the potential interactions, with the explicit description of many-body contributions being significant. [ABSTRACT FROM AUTHOR]

The influence of light spectral properties on circadian rhythms is of substantial interest to laboratory-based investigation of the circadian system and to field-based understanding of the effects of artificial light at night. The trade-offs between intensity and spectrum regarding masking behaviors are largely unknown, even for well-studied organisms. We used a custom LED illumination system to document the response of wild-type house mice (Mus musculus) to 1-h nocturnal exposure of all combinations of four intensity levels (0.01, 0.5, 5 and 50 lx) and three correlated color temperatures (CCT; 1750, 1950 and 3000 K). Higher intensities of light (50 lx) suppressed cage activity substantially, and consistently more for the higher CCT light (91% for 3000 K, 53% for 1750 K). At the lowest intensity (0.01 lx), mean activity was increased, with the greatest increases for the lowest CCT (12.3% increase at 1750 K, 3% increase at 3000 K). Multiple linear regression confirmed the influence of both CCT and intensity on changes in activity, with the scaled effect size of intensity 3.6 times greater than that of CCT. Activity suppression was significantly lower for male than for female mice. Assessment of light-evoked cFos expression in the suprachiasmatic nucleus at 50 lx showed no significant difference between high and low CCT exposure. The significant differences by spectral composition illustrate a need to account for light spectrum in circadian studies of behavior, and confirm that spectral controls can mitigate some, but certainly not all, of the effects of light pollution on species in the wild.

Photomultiplication-type organic photodetectors (PM-OPDs) have been stimulating more and more researchers' interest owing to their extremely high external quantum efficiency (EQE). To prepare high-performance PM-OPDs with a broadband spectral response range from visible to near-infrared and investigate the role of energy levels of the donor and acceptor on its responsiveness, the non-fullerene acceptor Y6 was added into the P3HT:PC71BM system in this work. The photomultiplication phenomenon with the highest EQE has been achieved under both forward and reverse bias when the ratio of Y6 in two acceptors approaches 80 wt. %. The introduction of Y6 not only promotes the formation of moderate hole traps in the active layer but also results in an appropriate amount of low injection barriers to allow more electron injection from the external circuit. Therefore, the spectral response of the device with 80 wt. % Y6 has been broadened from 750 to 950 nm, and the champion EQE of 15 691% at 10 V and 7639% at −20 V at 850 nm was achieved. This work reveals the importance of hole-trapping ability determined by the energy level difference between the donor and the acceptor for the selection of the multiplication system and provides a scheme for the design of high-performance broadband PM-OPDs. [ABSTRACT FROM AUTHOR]

Recently, we predicted theoretically that in cavities that support several longitudinal modes, strong coupling can occur in very different manners, depending on the system parameters. Distinct longitudinal cavity modes are either entangled with each other via the material or independently coupled to the exciton mode. Here, we experimentally demonstrate the transition between those two regimes as the cavity thickness is gradually increased while maintaining fixed coupling strength. We study the properties of the system using reflection and emission spectroscopy and show that even though the coupling strength is constant, different behavior in the spectral response is observed along the coupling–decoupling transition. In addition, we find that in such multimode cavities, pronounced upper polariton emission is observed, in contrast to the usual case of a single-mode cavity. Furthermore, we address the ultrafast dynamics of the multimode cavities by pump–probe spectroscopic measurements and observe that the transient spectra significantly change through the transition. [ABSTRACT FROM AUTHOR]

Using Bayesian spectroscopy, we performed spectral decomposition of gate modulation (GM) spectra measured in a pentacene organic field-effect transistor to understand comprehensively the optical nonlinear response due to GM and hole injection. Although GM spectra contain a variety of spectral components, by Bayesian spectroscopy, we can specify the role of each component in the nonlinear response by performing model selection that chooses the spectral components needed to explain the data without preconceptions. For a GM spectrum under positive GM, Bayesian spectroscopy shows that nonlinear responses by the change in polarizability dominate the GM spectrum among several types of Stark signals induced by the GM electric field, which is a physically valid conclusion. For GM spectra under negative GM where gate-induced carriers are injected, Bayesian spectroscopy succeeds in completely elucidating the spectral structure, which is composed of the two types of Stark signals due to changes in the polarizability and the dipole moment, bleaching, and gate-induced absorption signals. A pentacene film is known to have solid and isolated molecular phases, which may give different spectral responses. Therefore, we compared a model that treats these responses equally and a model that distinguishes them. Bayesian spectroscopy selects the latter models for all GM spectra, revealing statistically that nonlinear optical effects and hole injection effects are different in these phases. [ABSTRACT FROM AUTHOR]

In this work, a novel Y-NaBi(MoO 4) 2 @NaYF 4 :Yb, Tm composite was successfully synthesized for the first time by hydrothermal method. The lamellar Y-NaBi(MoO 4) 2 was dispersed on the surface of the hexagonal prism NaYF 4 :Yb, Tm without aggregation. The composite achieved a broad spectral response. The NaYF 4 :Yb, Tm absorbed near-infrared light and emitted ultraviolet and visible light by the energy transfer upconversion process. The emitted light was reabsorbed by Y-NaBi(MoO 4) 2 through the fluorescence resonance energy transfer process. Moreover, the doping of Y3+ ions enhanced the light response capability of the composite. The experimental results revealed that the photocatalytic degradation efficiency of ciprofloxacin (CIP) reached 96.2 % after 180 min of illumination under simulated sunlight. Meanwhile, the degradation pathways and attack sites of CIP were intensively investigated by liquid chromatography-mass spectrometry analysis and density functional theory theoretical calculations. The upconversion process, the separation of photogenerated carriers and rare earth metal ion doping all contributed to the high effective photodegradation. This work provided a new strategy for effective utilization of solar energy for the degradation of emerging pollutants to mitigate environmental pollution. [ABSTRACT FROM AUTHOR]

Metamaterial absorbers show great potential in many scientific and technological applications by virtue of their sub-wavelength and easy-to-adjust structure, with bandwidth as an important standard to measure the performance of the absorbers. In this study, our team designed a new broadband absorber, which consists of an indium arsenide (InAs) disk at the top, a zinc selenide (ZnSe)-chromium (Cr) stacked disk in the middle and a metal film at the bottom. Simulation results show that the absorber has remarkable absorptivity properties in the mid-long infrared band. In a wavelength range of 5.71–16.01 μm, the average absorptivity is higher than 90%. In the band of 5.86–15.49 μm, the absorptivity is higher than 95%. By simulating the electromagnetic field diagram at each resonant frequency, the reason for high broadband absorptivity is obtained. We also constructed Poynting vector diagrams to further elucidate this phenomenon. Next, we analyzed the influence of different materials and structural parameters on absorptivity properties and tested spectral response at different polarization angles and oblique incidence of the light source in the TM and TE modes. When the source is normally incident, the absorber shows polarization insensitivity. When the angle is 40°, absorptivity is still high, indicating that the absorber also possesses angle insensitivity. The broadband absorber proposed by us has good prospects in infrared detection and thermal radiators. [ABSTRACT FROM AUTHOR]

When changing habitat during migration or ontogenesis, fish encounter changes of the visual environment, among which the most important is the spectral composition of light and turbidity. This leads to changes in the behavior, morphology, and physiology of the visual system, in particular, spectral sensitivity, which is determined by the properties of visual pigments. The masked greenling Hexagrammos octogrammus has an additional factor that shapes effective spectral sensitivity—the presence of densely bright orange cornea which reversibly changes its density depending on the state of light/dark adaptation. However, it is unknown to what extent the properties of visual pigments are matched to spectral properties of the developing cornea at the final stage of metamorphosis during migration of juveniles from pelagic to coastal environments. The findings of this microspectrophotometric study show that the range of the spectral sensitivity of rods and cones in juveniles is much wider than in adults, with a shift in the sensitivity of a significant part of the cells to shorter wavelengths. The reason for this is the large variation in the ratio of chromophores A1:A2 in the pigment mixture in each cell and possible expression of new opsins. This also indicates the asynchrony of pigment transformations in different types of photoreceptors and the incompleteness of these transformations on the eve of the transition to bottom life in shallow water. [ABSTRACT FROM AUTHOR]

Individual differences are a prominent feature of normal color vision and range from variations in sensitivity to perception and color naming. Corrections for differences in spectral sensitivity are common, and there is growing interest in calibrating displays for the sensitivity of an individual observer. In contrast, few studies have explored calibrations for aspects of color appearance. We developed a technique for adjusting images based directly on an individual's hue percepts and illustrate the principle of the approach using a set of hue scaling functions measured previously for a large sample of color‐normal observers (Emery et al. PNAS 2023). Colors in an image are mapped onto the average scaling function to define the hue perceived by the average “standard observer.” This hue is then mapped back to the chromaticity that would elicit the same response in any individual observer. With this correction, different observers – each looking at physically different images calibrated for their own hue percepts – should in principle agree on the perceived colors. Adjustments of this kind could be easily implemented on standard displays, because they require only measures of hue percepts and not spectral sensitivity, and could lead to greater consistency in the perception and communication about color across individuals with potentially widely different perceptual experiences of color. [ABSTRACT FROM AUTHOR]

Porous photonic structures have greatly advanced large‐scale radiative cooling application owing to its satisfying optical properties, easy‐designation, and low cost. However, current reported porous radiative cooling materials mainly focuses on uniform or random pore distribution structure, which failed to achieve precise spectrum control for sunlight and mid‐infrared light, thereby weakening the radiative cooling performance. Herein, gradient structural porous metamaterials (GSPMs) are proposed and successfully constructed for maximizing cooling effectiveness based on step‐by‐step freeze‐casting technology. The designed GSPMs with gradient micro‐nano porous structure can wide‐range scatter entire solar spectrum while possess gradual refractive index transition to increase air‐medium interface absorption at mid‐infrared regions. Notably, solar reflectivity and mid‐infrared emissivity of GSPMs reach 97.3% and 97.6%, achieving maxinum cooling temperature of 8.7 °C and net cooling power of 94.1 W m−2, presenting a higher cooling effect than random porous materials. Moreover, GSPMs enable achieve compatibility with color aesthetic and cooling superiorities due to selective spectra response behavior, as well as can be applied in building materials, realizing efficient energy saving and CO2 emission reduction. This work proposed gradient porous structure can achieve highly efficient daytime radiative cooling, offering new possibilities in the structure design of next‐generation porous radiative cooling materials. [ABSTRACT FROM AUTHOR]

Luminance is the fundamental photometric quantity representing the technical meaning of brightness. It is usually measured from a distance using a matrix sensor, which is the basis of the professional instrument. However, specific technical requirements must be fulfilled to achieve accurate results. This paper considers whether modern high-resolution smartphone cameras are suitable for luminance measurements. Three cameras from high-end smartphones were evaluated on a dedicated laboratory stand. The sensors' output characteristics showed relatively good linearity of the individual R, G, and B channels. Unfortunately, the spectral sensitivities were unfavorable, as the minimum error achieved was about 17%. This device is classified outside the generally accepted quality scale for photometric instruments. The presented investigation confirmed that none of the high-resolution smartphone cameras tested was suitable for use as a universal luminance camera. However, one of the test devices can be developmental if restrictively calibrated and used only in a specialistic laboratory stand. Using a smartphone (or only its camera) for luminance measurements requires proper advanced calibration. It is possible, but it limits us to only dedicated applications. The pilot study presented in this paper will help create a suitable test stand for spectacle vision systems, e.g., virtual reality equipment. [ABSTRACT FROM AUTHOR]

A novel method to derive surface temperatures from aerial thermography is proposed. Its theoretical foundation, details regarding the implementation, relevant sensitivities, and its application on a day and night survey are presented here. The method differs from existing approaches particularly in two aspects: first, a three-dimensional sampling approach is used to determine the reflected thermal radiation component. Different surface classes based on hyperspectral classification with specific properties regarding the reflection and emission of thermal radiation are considered in this sampling process. Second, the method relies on a detailed, altitude-dependent, directionally and spectrally resolved modelling of the atmospheric radiation transfer and considers the spectral sensitivity of the sensor used. In order to accurately consider atmospheric influences, the atmosphere is modelled as a function of altitude regarding temperature, pressure and greenhouse gas concentrations. The atmospheric profiles are generated specifically for the time of the survey based on measurements, meteorological forecasts and generic models. The method was initially developed for application in urban contexts, as it is able to capture the pronounced three-dimensional character of such environments. However, due to the detailed consideration of elevation and atmospheric conditions, the method is also valuable for the analysis of rural areas. The included case studies covering two thermographic surveys of city area of Graz during daytime and nighttime demonstrate the capabilities and feasibility of the method. In relation to the detected brightness temperatures apparent to the sensor, the determined surface temperatures vary considerably and generally cover an increased temperature range. The two processed surface temperature maps of the city area of Graz are finally used to validate the method based on available temperature recordings. [ABSTRACT FROM AUTHOR]

Background: Radiochromic film (RCF) dosimeters with their high spatial resolution and tissue equivalent properties are conveniently used for two‐dimensional and small‐field dosimetry. OC‐1 is a new model of RCF dosimeter that was commercially introduced recently. Due to its novelty there is a need to characterize its response in various radiation beam types. Purpose: To study the response of OC‐1 RCFs to megavoltage clinical x‐ray, electron, and proton beams, as well as kilovoltage x‐ray beams used in a small animal research irradiator. Materials and methods: OC‐1 RCFs were cut into ∼4 × 4 cm2 pieces. RCF samples were irradiated at various dose levels in the range 0.5–120 Gy using different modalities; a small animal radiation research platform (SARRP) (220 kVp), a medical linear accelerator (6 MV, 10 MV, 15 MV, 6 MV FFF, 10 MV FFF photon beams, as well as 6 and 20 MeV electron beams), and a gantry‐mounted proton therapy synchrocyclotron. In order to study any dependency on the fractionation scheme, same dose was delivered at several fractions to a set of films. Different dose rates in the range 200–600 MU/min were delivered to a set of films to investigate any dose rate dependency. The films were scanned pre‐irradiation and at 48 h post‐irradiation using a flatbed scanner. The net optical density (OD) was measured for red, green, and blue color channel for each film. The orientation dependency was studied by scanning the films at eight different orientations. In order to study the temporal evolution of the response of the films, film samples were irradiated at 10 and 50 Gy using 6 MV photon beams and were scanned upon irradiation at certain time intervals up to 3 months. The spectral response of the films were studied over the visible range using a spectrometer. Results: For megavoltage photon, electron, and plateau region of the proton beams, we did not observe a significant dependency on the beam quality, dose rate, and fractionation scheme. At the kV beam, an unusual over‐response was observed in the films' net OD. An orientation dependency in the response of the films with a sinusoidal trend was observed. The response of the films increased with time following a double or triple exponential trend. The spectral absorption peaks were blue‐shifted with dose. Conclusion: OC‐1 RCFs were found to be reliable dosimeters with no significant energy dependency in MV range for photon and electron beams including the FFF beams. They over‐respond when irradiated by kV x‐ray beams compared to MV x‐ray beams. Caution must be exercised to maintain the orientation of the films when scanning. Due to the temporal growth in the net OD of the films, same post‐irradiation time interval must be used for scanning the calibration and test films. [ABSTRACT FROM AUTHOR]

This paper proposes a novel framework for the random vibration fatigue assessment of thin‐walled plate with multiple holes based on the fatigue damage response spectrum method. Compared with other frequency‐domain evaluation methods, this framework fully exploits the dynamic characteristics of complex structures, decoupling the external excitation characteristics from the spatial characteristics of the structural response. This approach significantly enhances evaluation efficiency by avoiding the complex calculations associated with stress response spectral moments. The proposed method is employed to evaluate the contribution of each mode to the overall damage, additionally, the stress mode shapes are used to identify and refine the mesh around fatigue hotspots. Modal damage contribution factors are proposed to identify the key modes. By leveraging both structural dimension reduction and modal reduction techniques, the proposed framework can swiftly and accurately locate fatigue hotspots within complex structures and conduct precise fatigue assessments using the Absolute Sum ‐ Square Root of the Sum of Squares hybrid method. Finite element simulation analysis is conducted on a single‐lap structure containing numerous circular openings, validating the accuracy and efficiency of the proposed stochastic vibration fatigue assessment. Highlights: A framework for assessing random vibration fatigue of thin‐walled plate with localized featuresEmploy stress modes to pinpoint the locations of critical fatigue holesUtilize modal damage contribution factors to identify key modesImplement damage combination considering the identified key modes [ABSTRACT FROM AUTHOR]

Traditional silicon are expected to be integrated with emerging halide perovskites to form semiconductor heterostructures, which can facilitate the realization of more modern electronics and optoelectronics but not only solar cells. Currently, the deposition of perovskite films onto silicon substrates predominantly relies on spin-coating techniques, which inherently pose challenges, such as stringent growth prerequisites, compromised film integrity, and inability to foster robust interfacial tuning between the silicon and perovskite films. In this Letter, we report the epitaxial growth of a (100)-oriented CsPbBr3 film directly on a p-type silicon (100) substrate by pulsed laser deposition (PLD), which offers precision control over the interface between the substrate and film. This p-Si/n-CsPbBr3 semiconductor heterostructure manifests distinct p–n heterojunction behavior, characterized by current rectification in the dark state, which indicates the efficient charge separation and transport mechanisms. The device demonstrates visible photodetection capabilities from 400 to 700 nm, showcasing versatility in spectral response. Notably, under 520 nm laser illumination, the device exhibited a remarkable responsivity of 780 mA/W due to electron tunneling from silicon to perovskite film as a direct result of the epitaxial interface, coupled with millisecond-scale response and recovery times, highlighting its potential for high-speed and sensitive photodetector applications. These findings underscore the significant promise of PLD-mediated growth of high-quality epitaxial halide perovskite films on silicon substrates and the formation of heterostructure as a viable route toward complex thin superlattices and integrated devices. [ABSTRACT FROM AUTHOR]

The photomultiplication type organic photodetectors (PM‐OPDs) are prepared with structure of ITO/PNDIT‐F3N/F8BT/Y6‐1O:P3HT (100:3, wt/wt)/Al, containing hole traps formed with P3HT surrounded by Y6‐1O in active layers. The PM‐OPDs exhibit external quantum efficiency (EQE)>100% in the spectral response range from 310 to 910 nm, resulting from electron tunneling injection assisted by trapped hole near ITO electrode. The incorporation of F8BT buffer layers can induce the markedly decreased dark current density (JD) due to the large electron injection barrier. The light current density (JL) of PM‐OPDs exhibits slightly decreased by inserting F8BT buffer layers due to the enhanced electron tunneling injection assisted by the more trapped holes near ITO electrode. The signal‐to‐noise ratio (SNR) of PM‐OPDs achieves over 40‐fold increment by inserting appropriate thickness of F8BT buffer layers, resulting from the markedly decreased JD and reasonably high JL. The optimal PM‐OPDs exhibit excellent photodetection capability with EQE of 4200% at 360 nm and 6600% at 850 nm, associated with the specific detectivity of 3.9 × 1011 Jones at 360 nm and 9.7 × 1011 Jones at 850 nm. [ABSTRACT FROM AUTHOR]

Fast photoluminescence and scintillation with a Stokes shift larger than 1 eV is achieved in hetero‐ligand metal–organic framework (MOF) crystals comprising inorganic linking nodes and fluorescent conjugated ligands. By finely engineering the MOF composition with the use of ligands with strictly complementary emission and absorption properties and highly delocalized molecular electronic orbitals, the singlet excitons diffusion is enhanced through the ligand framework, fully exploiting both Förster and Dexter energy transfer mechanisms. This allows for the sensitization of energy acceptor ligand fluorescence by ultrafast non‐radiative energy transfer with a rate up to the THz range. This efficient antenna effect instantly activates the MOF scintillation with a Stokes shift as large as 1.3 eV in the blue spectral range, matching the highest sensitivity spectral window of the best photodetector available. This is obtained using a minimal doping level of the energy acceptor species, with a consequent elimination of emission re‐absorption that allows the achievement of a 500% increment of the MOFs scintillation efficiency and the detection of the radioactive krypton isotope 85Kr from the gas phase with an improved sensitivity compared with the reference material. [ABSTRACT FROM AUTHOR]

Sapphire fibers are becoming a research hotspot for high-temperature sensing in extreme environments due to their high melting point, wide transmission band and superior thermal stability. Nevertheless, the preparation of high-quality, few-mode, large-length sapphire fibers is still a major challenge for further application. Here, we have successfully fabricated high-quality sapphire fibers with a minimum diameter of ∼16 μm and a maximum length of more than 50 m using a state-of-the-art laser-heated pedestal growth system, which, to the best of our knowledge, is the size record for single-crystal fibers. Besides, the anisotropic growth behavior and mechanical properties were investigated in detail, demonstrating that c-oriented sapphire fibers present higher high-temperature tensile strength and superior creep resistance compared with a- and m-oriented sapphire fibers. Further reasearch demonstrates that the tensile strength increases dramatically with decreasing diameter, with the 30 μm-diameter sapphire fibers achieving a tensile strength of more than 8000 MPa and a maximum strain over 20 000 με, both of which are more than twice those of conventional sapphire fibers. Furthermore, a fiber Bragg grating was fabricated within a 30 μm-diameter sapphire fiber for the first time by the femtosecond laser line-by-line scanning method, exhibiting few-mode and stable spectral response in the range of 20–1600 °C with a maximum sensitivity of 40.45 pm °C−1 at 1600 °C. This work provides a feasible approach for the preparation of sapphire fibers without size limitation, and demonstrates huge potential of ultra-fine sapphire fibers for applications in harsh environments and strain sensing. [ABSTRACT FROM AUTHOR]

Perceptual segregation of complex sounds such as speech and music simultaneously emanating from multiple sources is a remarkable ability that is common in humans and other animals alike. Unlike animal physiological experiments with simplified sounds or human investigations with spatially broad imaging techniques, this study combines insights from animal single-unit recordings with segregation of speech-like sound mixtures. Ferrets are trained to attend to a female voice and detect a target word, both in presence and absence of a concurrent equally salient male voice. Recordings are made in primary and secondary auditory cortical fields, and in frontal cortex. During task performance, representation of the female words becomes enhanced relative to the male in all, but especially in higher cortical regions. Analysis of the temporal and spectral response characteristics during task performance reveals how speech segregation gradually emerges in the auditory cortex. A computational model evaluated on the same voice mixtures replicates and extends these results to different attentional targets (attention to female or male voices). These findings underscore the role of the principle of temporal coherence whereby attention to a target voice binds together all neural responses coherently modulated with the target, thus ultimately forming and extracting a common auditory stream. Ferrets learned to attend and react to words of a female voice embedded in a speech mixture with a male. Recordings in auditory cortex reveal rapidly enhanced responses to the attended female voice and a simultaneous suppression of the male distractor. [ABSTRACT FROM AUTHOR]

We demonstrated high-performance 8.9 μ m cutoff wavelength nBn InAs/InAsSb type-II strained-layer superlattice (T2SL). These detectors exhibit a long minority carrier (hole) lifetime of 1.2 μ s at 80 K, high quantum efficiency of 40% for back-side illuminated devices without antireflection coating, and low dark current density of 4.6 × 10−6 A/cm2 at 80 K. We measured absorption, minority carrier (hole) lifetime, quantum efficiency, and spectral response as a function of the temperature and applied bias. We investigated the temperature dependence of the hole diffusion length and mobility and found that their values increase with temperature from 1.3 μ m and 6.5 cm2/Vs at 30 K to 6.5 μ m and 36 cm2/Vs at T = 90 K. We compared the measured diffusion length and mobility of holes in long-wavelength infrared (LWIR) T2SL with these parameters of a high-performance mid-wavelength infrared (MWIR) T2SL. Unexpectedly, hole mobility in LWIR T2SL was found to be higher than in MWIR that is contrary to the theoretical predictions. [ABSTRACT FROM AUTHOR]

We demonstrate room temperature operation of mid-wave infrared photodetectors leveraging a guided mode resonance architecture and bulk alloy InAsSb absorbers. Room temperature operation with low dark current is achieved by using detector structures with ultra-thin (150 , 250 nm) absorbers leveraging the strong confinement enabled by the guided mode architecture. Devices with 1D and 2D grating arrays are fabricated and characterized, and compared to unpatterned detector devices. We see enhancement in the detectors' optical response associated with coupling to both TE- and TM-polarized guided modes and good agreement between experimental and theoretically-predicted behavior. We show strong enhancement for unpolarized light incident on 2D grating arrays, with a broader spectral response than observed for polarized light incident upon 1D grating GMR detectors. The bulk InAsSb detectors presented in this work offer enhanced performance at room temperature for a range of imaging and sensing applications. [ABSTRACT FROM AUTHOR]

Soil spectroscopy offers a method for quantitatively analysing soil chromophores and employing a screening approach. However, utilizing general models with this data at once doesn’t consistently yield accurate results in determining soil parameters. Ambiguities in response within certain domains of the reflectance spectrum are observed. To address this issue, a method is proposed where quantities associated with spectral response are outputted within well-defined domains corresponding to specific parameters. This article introduces a novel approach centred on identifying features from reflectance spectra to assess soil properties and mitigate issues arising from a heterogeneous soil dataset. The focus is on swiftly automating the classification of soil spectral data by extracting features directly related to the varied composition of chromophores in the samples. These features are categorized for each chromophore parameter and analysed using linear discriminant analysis (LDA). The study employs the ‘309 soil samples’ from the GEO-CRADLE open spectral soil library in Greece. Specifically, relevant data from six spectral responses are extracted to separate and quantify certain soil parameters such as clay content, NO3− levels, and SOM (Soil Organic Matter), despite their interrelations. We developed a method to visually represent the determination outcomes quantitatively by establishing three threshold parameter values: 1.6% for SOM, 19% for clay, and 13.6 ppm for NO3−. These determinations will span the explored ranges of ’0.3 to 4.18%’ for SOM, “3 to 48%” for clay, and ’0 to 661.2 ppm’ for NO3−. Utilizing supervised LDA proves notable classification rates of 93.3% for the SOM task, 90% for the Clay task, and 86.6% for NO3− with the specific cut-off value parameter. The final result is presented as a map showing the positions of various prediction samples, highlighting the percentages of clay and organic matter relative to 19% and 1.6%, respectively, as well as the nitrate concentration in these samples relative to 13.6 ppm. [ABSTRACT FROM AUTHOR]

Spectroradiometry, radiometry, and dosimetry are employed for the measurement of ultraviolet radiation (UVR) irradiance and non‐ionizing exposure. Different types of UVR dosimeter have been developed for measuring personal and environmental UVR exposures since film dosimetry was pioneered in the 1970s. An important type of dosimeter is the thin film variant, which contains materials that undergo changes in optical absorbance when exposed to UVR. These changes can be measured at a specific wavelength using a spectrophotometer. Thin film dosimeters allow UVR exposure measurements on humans at various body sites during daily activities, as well as on plants, animals, and any sites of interest when utilized in a field environment. This review examines the properties and applications of five types of thin film UVR dosimeter that have different dynamic exposure limits and spectral responses. Polysulphone, with a spectral response approximating the human erythema action spectrum, was one of the first materials employed in thin film form for the measurement of UVR exposures up to 1 day, and up to 6 days with an extended dynamic range filter. Polyphenylene oxide has been characterized and employed for personal UVR exposure measurements up to approximately four summer days and has also been used for long‐term underwater UVR exposures. Phenothiazine and 8‐methoxypsoralen have been reported as suitable for the measurement of longer wavelength UVA exposures. Finally, polyvinyl chloride with an extended dynamic exposure range of over 3 weeks has been shown to have predominantly a spectral response in the UVB and extending up to 340 nm. [ABSTRACT FROM AUTHOR]

Photochromic yttrium oxyhydride, YHO, has excellent properties as a responsive solar control material, in particular due to its color-neutral darkening. In this work, we have investigated YHO's spectral response to the solar AM 1.5 spectrum to evaluate how the total photon activation flux changes as a function of thickness and wavelength. The calculations are based on ellipsometry measurements in the 240–2000 nm range. Our results show that the UV light absorption saturates at around 400 nm thick film, while blue light (>400 nm) continues to provide photoactivation well beyond 1 μm thickness. Understanding the spectral response and absorption per unit time of activating photons as a function of material thickness is important for evaluating the material or coating for applications. [ABSTRACT FROM AUTHOR]

Soil salinization typically exerts a highly negative influence on soil productivity, crop yields, and ecosystem balance. As a typical region afflicted by soil salinization, the soda saline–alkali soils in the Songnen Plain of China demonstrate a clear cracking phenomena. Nevertheless, the overall spectral response to the cracked soil surface has scarcely been studied. This study intends to study the impact of salt parameters on the soil cracking process and enhance the spectral measurement method used for cracked salt-affected soil. To accomplish this goal, a controlled desiccation cracking experiment was carried out on saline soil samples. A gray-level co-occurrence matrix (GLCM) was calculated for the contrast (CON) texture feature to measure the extent of cracking in the dried soil samples. Additionally, spectroscopy measurements were conducted under different surface conditions. Principal component analysis (PCA) was subsequently performed to downscale the spectral data for band integration. Subsequently, the prediction accuracy of back-propagation artificial neural network (BP-ANN) models developed from the principal components of spectral reflectance was compared for different salt parameters. The results reveal that salt content is the dominant factor determining the cracking process in salt-affected soils, and that cracked soil samples had the highest model prediction accuracy for different salt parameters rather than uncracked blocks and 2 mm comparison soil samples. Furthermore, BP-ANN prediction models combining spectral response and CON were further developed, which can significantly enhance the prediction accuracy of different salt parameters with R2 values of 0.93, 0.91, and 0.74 and a ratio of prediction deviation (RPD) of 3.68, 3.26, and 1.72 for soil salinity, electrical conductivity (EC), and pH, respectively. These findings provide valuable insights into the cracking mechanism in salt-affected soils, thereby advancing the field of hyperspectral remote sensing for monitoring soil salinization. Furthermore, this study also aids in enhancing the design of spectral measurements for saline–alkali soils and is also helpful for local soil remediation with supporting data. [ABSTRACT FROM AUTHOR]

Liquefaction can significantly alter the ground response. However, no existing design spectrum accounts for the severity of soil liquefaction. This work aims to develop correction factors that can be used to adjust code-based design spectra to reflect the specific liquefaction susceptibility of a site. The correction factor is derived as the ratio of response spectra calculated by two types of 1D nonlinear site response analyses: effective stress analysis, which can model porewater pressure (PWP) generation, and total stress analysis. We considered seven real profiles and 200 motions in our analysis. Four combinations of soil nonlinear models and PWP generation models are also utilized to account for epistemic uncertainties. Results show that the response spectral ratio for liquefied sites typically falls below one for periods less than 1–2 s and rises above one for longer periods. Meanwhile, the response spectral ratio reflects the overall liquefaction susceptibility influenced by PWP, factor of safety, and liquefiable layer depth, while the liquefaction potential index (LPI) captures their complex interplay. Accordingly, we propose four LPI-dependent factors: three correction factors for peak ground acceleration, 0.2 s spectral acceleration (Sa), and 1.0 s Sa, and a long-period adjustment factor applicable for periods exceeding 1 s. The correction factors linearly decrease with increasing LPI, while the adjustment factor exhibits the opposite trend. A design spectrum for a liquefiable site can be readily constructed by adjusting the code-based design spectrum using the proposed correction factor, as illustrated in the example. This approach is applicable as long as LPI is available from a simplified liquefaction analysis or a liquefaction hazard map. [ABSTRACT FROM AUTHOR]

Accurate land surface temperature (LST) retrieval depends on precise knowledge of the land surface emissivity (LSE). Neglecting or inaccurately estimating the emissivity introduces substantial errors and uncertainty in LST measurements. The emissivity, which varies across different surfaces and land uses, reflects material composition and surface roughness. Satellite data offer a robust means to determine LSE at large scales. This study utilises the Normalised Difference Vegetation Index Threshold Method (NDVITHM) to produce a novel emissivity dataset spanning the last 40 years, specifically tailored for the Fennoscandian region, including Norway, Sweden, and Finland. Leveraging the long and continuous data series from the Advanced Very High Resolution Radiometer (AVHRR) sensors aboard the NOAA and MetOp satellites, an emissivity dataset is generated for 1981–2022. This dataset incorporates snow-cover information, enabling the creation of annual emissivity time series that account for winter conditions. LSE time series were extracted for six 15 × 15 km study sites and compared against the Moderate Resolution Imaging Spectroradiometer (MODIS) MOD11A2 LSE product. The intercomparison reveals that, while both datasets generally align, significant seasonal differences exist. These disparities are attributable to differences in spectral response functions and temporal resolutions, as well as the method considering fixed values employed to calculate the emissivity. This study presents, for the first time, a 40-year time series of the emissivity for AVHRR channels 4 and 5 in Fennoscandia, highlighting the seasonal variability, land-cover influences, and wavelength-dependent emissivity differences. This dataset provides a valuable resource for future research on long-term land surface temperature and emissivity (LST&E) trends, as well as land-cover changes in the region, particularly with the use of Sentinel-3 data and upcoming missions such as EUMETSAT's MetOp Second Generation, scheduled for launch in 2025. [ABSTRACT FROM AUTHOR]

Uvsq-Sat NG is a French 6U CubeSat (10 × 20 × 30 cm) of the International Satellite Program in Research and Education (INSPIRE) designed primarily for observing greenhouse gases (GHG) such as CO2 and CH4, measuring the Earth's radiation budget (ERB), and monitoring solar spectral irradiance (SSI) at the top-of-atmosphere (TOA). It epitomizes an advancement in CubeSat technology, showcasing its enhanced capabilities for comprehensive Earth observation. Scheduled for launch in 2025, the satellite carries a compact and miniaturized near-infrared (NIR) spectrometer capable of performing observations in both nadir and solar directions within the wavelength range of 1100 to 2000 nm, with a spectral resolution of 7 nm and a 0.15° field of view. This study outlines the preflight calibration process of the Uvsq-Sat NG NIR spectrometer (UNIS), with a focus on the spectral response function and the absolute calibration of the instrument. The absolute scale of the UNIS spectrometer was accurately calibrated with a quartz-halogen lamp featuring a coiled-coil tungsten filament, certified by the National Institute of Standards and Technology (NIST) as a standard of spectral irradiance. Furthermore, this study details the ground-based measurements of direct SSI through atmospheric NIR windows conducted with the UNIS spectrometer. The measurements were obtained at the Pommier site (45.54°N, 0.83°W) in Charentes–Maritimes (France) on 9 May 2024. The objective of these measurements was to verify the absolute calibration of the UNIS spectrometer conducted in the laboratory and to provide an extraterrestrial solar spectrum using the Langley-plot technique. By extrapolating the data to AirMass Zero (AM0), we obtained high-precision results that show excellent agreement with SOLAR-HRS and TSIS-1 HSRS solar spectra. At 1.6 μm, the SSI was determined to be 238.59 ± 3.39 mW.m−2.nm−1 (k = 2). These results demonstrate the accuracy and reliability of the UNIS spectrometer for both SSI observations and GHG measurements, providing a solid foundation for future orbital data collection and analysis. [ABSTRACT FROM AUTHOR]

This study presents a comprehensive simulation of a TiSe2‐based photodetector, an optoelectronic device adept at converting a spectrum of electromagnetic radiation spanning ultraviolet (UV), visible, and infrared wavelengths into electrical signals. The TiSe2 absorber material is characterized by a narrow direct bandgap of 1.2 eV, endowing the photodetector with superior optical and electronic attributes that enhance its photodetection capabilities. In‐depth analysis of the energy band diagram, the current‐voltage (J‐V) characteristics, and spectral responses is conducted. This article involves in methodical variations in the thickness, doping levels, and defect density across different layers to achieve optimal performance. The photodetector's current, JSC, and voltage, VOC are recorded at 37.30 mA cm−2 and 0.795 V, in turn. Additionally, the device achieves a peak responsivity, R of 0.67 A W−1 and a detectivity, D* of 12.9 × 1014 Jones at a wavelength of 920 nm. Notably, the spectral response is significantly enhanced between 760 and 1010 nm, indicating the photodetector's proficient detection of near‐infrared (NIR) light. The findings underscore the potential of TiSe2 as an effective material for photodetector applications, marking a significant advancement in the field and paving the way for future research endeavors in photodetector technology. [ABSTRACT FROM AUTHOR]

AbstractThe flame temperature is a crucial parameter in combustion, indicating heat generation and transfer. However, determining the correct temperature becomes challenging when flame emissivity is unknown. This article presents a multispectral 2D temperature field reconstruction method using particle swarm optimization and the Broyden–Fletcher–Goldfarb–Shanno algorithm, combined with multivariate extreme-value optimization. This method establishes an objective function based on the correlation between the true temperature and spectral data. The objective function was minimized by adjusting the emissivity, enabling the reconstruction of 2D temperature and emissivity images without assuming an emissivity model. Calibration with a multispectral camera yielded the spectral response coefficients, and three-time spline interpolation was used to verify the calibration data. The reconstructed 2D temperature field showed a mean absolute error (MAE) of 4.61 and structural similarity (SSIM) of 0.995. The reconstructed emissivity image had an MAE range of 0.04 to 0.053 and an SSIM range of 0.897 to 0.915. The system, tested on a butane flame, showed a temperature range of 1001 K to 1356 K, with an average temperature of 1194 K and emissivity values ranging from 0.3166 to 0.8621. The results align with the expected combustion process and radiation characteristics distribution of the butane flame. [ABSTRACT FROM AUTHOR]

High‐resolution infrared (IR) imaging technology holds substantial significance across diverse fields including biomedical imaging, environmental surveillance, and IR digital cameras. Current IR detectors used in commercial applications are based on ultra‐high vacuum‐processed traditional inorganic semiconductors like silicon or III‐V compounds (e.g., Si, Ge, and InGaAs). However, the rapid advancements in applications such as autonomous vehicles, virtual reality, and point‐of‐care healthcare are driving an escalating need for innovative imaging technologies. This review aims to bridge the gap by exploring solution‐processed semiconductor photodetectors (PDs), which offer distinct advantages including cost‐effectiveness, tunable spectral response, and potential for multiple‐exciton generation. These characteristics make them particularly suitable for optical communication, IR imaging, and biological monitoring applications. This review provides comprehensive insights into the research trends pertaining to solution‐processed IR detectors and imagers based on colloidal quantum dots, perovskites, organic compounds, and 2D materials. The review commences with the current market worth of image sensors, the fundamental principles of single‐pixel and multipixel array IR imagers, and key parameters used to assess IR detector performance. In essence, the review concludes with a summary of recent advancements and future prospects for next‐generation IR PD devices and their potential application as an IR imager. [ABSTRACT FROM AUTHOR]

• Network analysis of stimulation-induced spectral responses can identify increased excitability within the seizure onset zone (SOZ) • Prediction of SOZ sites is good in surgical success cases and poor in surgical failure cases. • Alignment of high centrality sites with SOZ sites that were targeted for surgical treatment may predict surgical outcome. While evoked potentials elicited by single pulse electrical stimulation (SPES) may assist seizure onset zone (SOZ) localization during intracranial EEG (iEEG) monitoring, induced high frequency activity has also shown promising utility. We aimed to predict SOZ sites using induced cortico-cortical spectral responses (CCSRs) as an index of excitability within epileptogenic networks. SPES was conducted in 27 epilepsy patients undergoing iEEG monitoring and CCSRs were quantified by significant early (10–200 ms) increases in power from 10 to 250 Hz. Using response power as CCSR network connection strengths, graph centrality measures (metrics quantifying each site's influence within the network) were used to predict whether sites were within the SOZ. Across patients with successful surgical outcomes, greater CCSR centrality predicted SOZ sites and SOZ sites targeted for surgical treatment with median AUCs of 0.85 and 0.91, respectively. We found that the alignment between predicted and targeted SOZ sites predicted surgical outcome with an AUC of 0.79. These findings indicate that network analysis of CCSRs can be used to identify increased excitability of SOZ sites and discriminate important surgical targets within the SOZ. CCSRs may supplement traditional passive iEEG monitoring in seizure localization, potentially reducing the need for recording numerous seizures. [ABSTRACT FROM AUTHOR]

As a payload of Tianwen-1 (TW-1), the Mars Mineral Spectrometer (MMS) is tasked with acquiring hyperspectral data of the Martian surface to detect material composition. Microdeformations in optical, mechanical, and thermal components result in the MMS experiencing spectral response distortion in orbit, leading to systematic changes in pixel central wavelengths and full width at half maximum (FWHM). Known as the spectral smile, this distortion compromises the accuracy of reflectance inversion and material composition detection. This study introduces a method for detecting the spectral smile through the Martian atmospheric absorption channel, capitalizing on the distinct characteristics of the atmospheric composition and absorption patterns of Mars. A suitable technical route for in-orbit spectral smile detection was established and tested using simulation experiments and MMS-acquired hyperspectral data. Results suggest that the proposed method can attain central wavelength shifts with a maximum error of 0.32 nm and FWHM variations with a maximum error of 1.95 nm. Employing in-orbit spectral smile detection markedly enhances the correction of Martian atmospheric absorption and provides technical support for Martian surface reflectance inversion. https://github.com/wubingnote/MMS-Spectral-Smile. [ABSTRACT FROM AUTHOR]

The fabrication and characterization of an all polymers‐based bulk heterojunction type organic photodiode having a narrowband response in the near‐infrared spectral region with full width at half‐maxima of 63 nm is reported. The active layer of the photodiode constitutes a 1:1 (by weight) blend of poly[4,8‐bis(5‐(2‐ethylhexyl)thiophen‐2‐yl)benzo[1,2‐b;4,5‐b']dithiophene‐2,6‐diyl‐alt‐(4‐(2‐ethylhexyl)‐3‐fluorothieno[3,4‐b]thiophene‐)‐2‐carboxylate‐2‐6‐diyl)] (PCE10) and poly{[N,N′‐bis(2‐octyldodecyl)‐naphthalene‐1,4,5,8‐bis(dicarboximide)‐2,6‐diy1]‐alt‐5,5′‐(2,2′‐dithiophene)} (N2200) deposited using solution processing. The device exhibits a linear dynamic range of 35 dB, response speed of 893 kHz, and specific‐detectivity of 109 Jones at 808 nm excitation wavelength. The narrowband response is achieved using the charge collection narrowing mechanism in a 2.7 μm thick junction device. [ABSTRACT FROM AUTHOR]

Our study demonstrates second harmonic generation (SHG) in a high confinement LiNbO3 rib waveguide through type-I birefringence phase matching of fundamental modes. The combination of micro-waveguide dispersion and material birefringence reveals unique SHG characteristics that complement the performance of standard LiNbO3 on insulator (LNOI) components. Dual-pump wavelength phase matching in the near-infrared and mid-infrared regions is shown in a given waveguide. These two wavelengths can be positioned in the 1.1–3.5 μm range or converge near 1.5 μm by adjusting the core waveguide size or through temperature tuning. A 25 °C temperature change enables a broad pump tunability band of 300 nm, ranging from 1350 to 1650 nm, with a conversion efficiency exceeding 40 %/W/cm2 within a single waveguide. A temperature tuning range of up to 900 nm is foreseen by tailoring the waveguide core size. In addition, a broadband response of 150 nm within the telecom window is demonstrated experimentally. The nonlinear waveguide, etched in a thin film membrane, is combined with titanium-indiffused waveguides to form a monolithic LiNbO3 component. This configuration provides low coupling losses of 0.8 dB and single-mode operation. It paves the way for a new generation of versatile and cost-effective frequency conversion components with wide-band spectral responses suitable for optical communications, environmental sensing, and quantum information processing. [ABSTRACT FROM AUTHOR]

Due to the excellent quantum conversion and spectral response characteristics of the AlGaN photocathode, it has become the most promising III-V group semiconductor photocathode in solar-blind signal photoconversion devices in the ultraviolet band. Herein, the influence factors of the time-resolved characteristics of the AlGaN photocathode are researched by solving the photoelectron continuity equation and photoelectron flow density equation, such as the AlN/AlGaN interface recombination rate, AlGaN electron diffusion coefficient, and AlGaN activation layer thickness. The results show that the response time of the AlGaN photocathode decreases gradually with the increase in AlGaN photoelectron diffusion coefficient and AlN/AlGaN interface recombination rate, but the response time of the AlGaN photocathode gradually becomes saturated with the further increase in AlN/AlGaN interface recombination rate. When the thickness of the AlGaN photocathode is reduced from 250 nm to 50 nm, the response time of the AlGaN photocathode decreases from 63.28 ps to 9.91 ps, and the response time of AlGaN photocathode greatly improves. This study provides theoretical guidance for the development of a fast response UV detector. [ABSTRACT FROM AUTHOR]

This paper presents the design of a strain-sensitive, dual ball-shaped tunable zone (DBT) taper structure for light intensity modulation. Unlike conventional tapered optical fibers, the DBT incorporates a central light field modulation zone within the taper. By precisely controlling the fusion parameters between single-mode fiber (SMF) and polarization-maintaining fiber (PMF), the ellipticity of the modulation zone can be finely adjusted, thereby optimizing spectral characteristics. Theoretical analysis based on polarization mode interference (PMI) coupling confirms that the DBT structure achieves a more uniform spectral response. In cantilever beam strain tests, the DBT exhibits high sensitivity and a highly linear intensity–strain response (R² = 0.99), with orthogonal linear polarization mode interference yielding sensitivities of 0.049 dB/με and 0.023 dB/με over the 0–244.33 με strain range. Leveraging the DBT's light intensity sensitivity, a temperature-compensated intensity difference and ratio calculation method is proposed, effectively minimizing the influence of light source fluctuations on sensor performance and enabling high-precision strain measurements with errors as low as ±6 με under minor temperature variations. The DBT fiber device, combined with this innovative demodulation technique, is particularly suitable for precision optical sensing applications. The DBT structure, combined with the novel demodulation method, is particularly well-suited for high-precision and stable measurements in industrial monitoring, aerospace, civil engineering, and precision instruments for micro-deformation sensing. [ABSTRACT FROM AUTHOR]

Perovskite can be used to prepare high-performance photodetectors due to its excellent optical properties. However, the detection range of perovskite photodetectors is mostly limited to the visible light range, restricting their further development and application. In recent years, combining perovskite with organic bulk heterojunctions to prepare photodetectors with broadband detection capability has proven to be an effective strategy. Through this approach, the response spectrum of the photodetector can be flexibly regulated, and organic compounds can improve the perovskite film quality by passivating defects and inhibit the penetration of water molecules in the air, thereby improving the device performance and stability. In this work, we propose and demonstrate the feasibility of combining MAPbI3 perovskite with PTB7-Th:COTIC-4F to prepare high-performance photodetectors with wide spectral response characteristics. With the assistance of an organic bulk heterojunction, the defects of perovskite crystals are effectively passivated, and the detection spectrum of the device is successfully extended to about 1100 nm. As a result, the responsivity achieved is 0.58 A/W, 1.19 A/W, and 1.41 A/W under laser illumination of 532 nm, 808 nm, and 980 nm, with the power density of 5 μW/cm2 at the bias voltage of −0.5 V, respectively, which is one of the best performances among vertical device structures of this type. Moreover, the stability of the final hybrid film has been greatly improved. This work provides a new approach to the preparation of high-performance and broadband perovskite photodetectors. [ABSTRACT FROM AUTHOR]

Recent years have received huge attention towards monitoring solar ultraviolet radiation due to ozone depletion caused by industrialization and urbanization. Ozone layer is a main significant constituent of the stratosphere and makes life possible on the earth's surface by absorbing the hazardous UV radiation. Adverse effects of UV radiations can be seen in different chemical and biological processes of plants and animals, it damages aquatic life, effects conservation and durability of materials and even human health and also shows its impact on global energy balance and climate change. Light-exposed tissues effected by photo oxidative stress causes and promotes diseases, including skin cancer, cataract and age-related macular degeneration. Ultraviolet (UV) radiation potentially damages the skin, the immune system and structures of the eye. Chronic UV exposure affects the cornea and lens, making effective UV protection crucial for all age groups. Monitoring of solar UV-B and UV-E radiations were performed by measuring the intensities of solar UV radiations using Kipps & Zonen radiometer sensors having spectral sensitivity. In this piece of work, three sites of Uttarakhand were selected for measurement of solar UVB and UV-E radiation and average summer peak of ultraviolet (ASPUV) and average winter peak ultraviolet (AWPUV) were calculated. Altitudinal, monthly and diurnal variations were observed and average summer and winter peak value were calculated. Natural solar UV-B level was minimum in January and maximum in months of June to September. It was found that the intensity of UV-B increases with increase in altitude and also sun's position, altitude, latitude, climate, pollution, dust and cloud affect the solar UV radiation. [ABSTRACT FROM AUTHOR]

Plant nitrogen concentration (PNC) is a key indicator reflecting the growth and development status of plants. The timely and accurate monitoring of plant PNC is of great significance for the refined management of crop nutrition in the field. The rapidly developing sensor technology provides a powerful means for monitoring crop PNC. Although RGB images have rich spatial information, they lack the spectral information of the red edge and near infrared bands, which are more sensitive to vegetation. Conversely, multispectral images offer superior spectral resolution but typically lag in spatial detail compared to RGB images. Therefore, the purpose of this study is to improve the accuracy and efficiency of crop PNC monitoring by combining the advantages of RGB images and multispectral images through image-fusion technology. This study was based on the booting, heading, and early-filling stages of winter wheat, synchronously acquiring UAV RGB and MS data, using Gram–Schmidt (GS) and principal component (PC) image-fusion methods to generate fused images and evaluate them with multiple image-quality indicators. Subsequently, models for predicting wheat PNC were constructed using machine-selection algorithms such as RF, GPR, and XGB. The results show that the RGB_B1 image contains richer image information and more image details compared to other bands. The GS image-fusion method is superior to the PC method, and the performance of fusing high-resolution RGB_B1 band images with MS images using the GS method is optimal. After image fusion, the correlation between vegetation indices (VIs) and wheat PNC has been enhanced to varying degrees in different growth periods, significantly enhancing the response ability of spectral information to wheat PNC. To comprehensively assess the potential of fused images in estimating wheat PNC, this study fully compared the performance of PNC models before and after fusion using machine learning algorithms such as Random Forest (RF), Gaussian Process Regression (GPR), and eXtreme Gradient Boosting (XGB). The results show that the model established by the fusion image has high stability and accuracy in a single growth period, multiple growth periods, different varieties, and different nitrogen treatments, making it significantly better than the MS image. The most significant enhancements were during the booting to early-filling stages, particularly with the RF algorithm, which achieved an 18.8% increase in R2, a 26.5% increase in RPD, and a 19.7% decrease in RMSE. This study provides an effective technical means for the dynamic monitoring of crop nutritional status and provides strong technical support for the precise management of crop nutrition. [ABSTRACT FROM AUTHOR]

Silicon photonic index sensors have received significant attention for label-free bio and gas-sensing applications, offering cost-effective and scalable solutions. Here, we introduce an ultra-compact silicon photonic refractive index sensor that leverages zero-crosstalk singularity responses enabled by subwavelength gratings. The subwavelength gratings are precisely engineered to achieve an anisotropic perturbation-led zero-crosstalk, resulting in a single transmission dip singularity in the spectrum that is independent of device length. The sensor is optimized for the transverse magnetic mode operation, where the subwavelength gratings are arranged perpendicular to the propagation direction to support a leaky-like mode and maximize the evanescent field interaction with the analyte space. Experimental results demonstrate a high wavelength sensitivity of − 410 nm/RIU and an intensity sensitivity of 395 dB/RIU, with a compact device footprint of approximately 82.8 μm2. Distinct from other resonant and interferometric sensors, our approach provides an FSR-free single-dip spectral response on a small device footprint, overcoming common challenges faced by traditional sensors, such as signal/phase ambiguity, sensitivity fading, limited detection range, and the necessity for large device footprints. This makes our sensor ideal for simplified intensity interrogation. The proposed sensor holds promise for a range of on-chip refractive index sensing applications, from gas to biochemical detection, representing a significant step towards efficient and miniaturized photonic sensing solutions. [ABSTRACT FROM AUTHOR]

With the development of wearable electronic technology, the flexible photodetectors have attracted widespread attention, and it is of great significance to develop flexible, eco‐friendly and low‐cost photodetectors. Cellulose paper, as a flexible, eco‐friendly, low‐cost, lightweight, customizable, biodegradable and renewable material, has received enthusiastic attention and rapid development in the field of photodetectors in recent years. In this review, it is focused on the research progress of paper‐based (PB) photodetectors. First, the fabrication methods of PB photodetectors are discussed, including electrode materials and optoelectronic functional materials. Then, this review systematically summarizes and analyzes the achievements of PB photodetectors on photoelectric performances (spectral response range, responsivity, detectivity, response/recovery times and on/off ratio) and flexibility characteristics (bending angle and bending cycle). In terms of key performance indicators, the PB photodetectors reported so far can detect multiple wavelengths of light from UV to near‐infrared with the maximum detectivity of 1013 Jones. In addition, the various applications of PB photodetectors is reviewed and discussed. Finally, it is look forward to the future development of PB photodetectors in terms of fabrication methods, photoelectric and flexible performances, and applications. With this review, it is hope that it will promoted the future development of PB photodetectors. [ABSTRACT FROM AUTHOR]

Broadening near‐infrared (NIR) spectral response by virtue of organic bulk heterojunction (BHJ) is intensively explored to enhance power conversion efficiency (PCE) of perovskite solar cells (PSCs). However, the complex photovoltaic morphology and undesirable conductivity in BHJ structure can lead to the severe loss of photovoltaic performance, which are still urgent challenges for the commercialization of integrated PSCs (IPSCs). Recently, the gradual development of pseudo‐planar heterojunction (PPHJ) structure with excellent vertical phase separation and improved charge transfer can hopefully provide more opportunities for IPSCs. Herein, an optimization strategy is reported employing PPHJ structure with hydrophobic long alkyl chains as the NIR light‐absorbing layer in the devices, with which the light response of the IPSCs is extended to 920 nm. Owing to the lone electron pairs in the sulfur atoms, D18‐Cl has functioned as an effective additive that can effectively modulate the growth of the perovskite and passivate the defects. As a result, the optimized device has achieved an impressive PCE of 23.25%, while the short‐circuit current is enhanced from 22.93 to 25.14 mA cm−2. The long‐term and humidity stability of integrated perovskite/PPHJ solar cells are significantly elevated compared with IPSCs based on BHJ. [ABSTRACT FROM AUTHOR]

We present a study of high-cadence, high-precision optical light curves from the TESS satellite of 67 blazars in the southern sky. We provide descriptive flux statistics, power spectral density (PSD) model parameters, and characteristic variability timescales. We find that only 15 BL Lacertae objects (BLLs) and 18 flat spectrum radio quasars (FSRQs) from the initial 26 and 41, respectively, exhibit statistically significant variability. We employ an adapted power spectral response method to test the goodness of fit for the PSD function to three power-law variant models. From our best-fitting description of the PSD, we extract the high-frequency power-spectral slopes, and if present, determine the significant bend or break in the model to identify characteristic timescales. We find no significant difference in the excess variance or rms scatter between blazar subpopulations. We identify a linear rms–flux relation in ∼69% of our sample, in which ∼20% show a strong correlation. We find that both subpopulations of blazars show power spectral slopes of α ∼ 2 in which a broken power-law best fits five BLLs and six FSRQs and a bending power-law best fits one BLL and five FSRQs. The shortest timescales of variability in each light-curve range widely from minutes to weeks. Additionally, these objects' characteristic timescales range from ∼0.8 to 8 days, consistent with optical variability originating in the jet. [ABSTRACT FROM AUTHOR]

Photocatalytic H2 evolution by water splitting is a promising approach to address the challenges of environmental pollution and energy scarcity. Graphitic carbon nitride (g‐C3N4) has emerged as a star photocatalyst because of its numerous advantages. To address the limitations of traditional g‐C3N4, namely its inadequate visible light response and rapid recombination of photogenerated carriers, we employed a schiff base reaction to synthesize −C=N− doped g‐C3N4. The introduction of −C=N− groups at the bridging nitrogen sites induced structural distortion in g‐C3N4, facilitating n‐π* electronic transitions from the lone pair electrons of nitrogen atom and extending light absorption up to 600 nm. Moreover, the presence of heterogeneous π‐conjugated electron distribution effectively traps photogenerated electrons and enhances charge carrier separation. Benefiting from its expanded spectral response range, unique electronic properties, increased specific surface area, the doped g‐C3N4 exhibited outstanding photocatalytic H2 evolution performance of 1050.13 μmol/g/h. The value was 5.9 times greater than the pristine g‐C3N4. [ABSTRACT FROM AUTHOR]

Background/Objectives: Fragility fractures of the pelvis (FFP) are characterized by inadequate trauma to a structurally compromised bone, primarily in osteoporosis. Conventional CT studies can be inadequate in identifying FFPs. An MRI of the pelvis is considered the gold standard in diagnosing FFPs. Spectral CT or Dual-Energy CT may have comparable diagnostic accuracy. It provides additional insights into associated bone marrow edema. The aim of this prospective monocentric study is to evaluate the diagnostic accuracy of Spectral CT compared to the gold standard MRI in diagnosing FFP. Methods: Over a 2-year period, patients presenting in the emergency department with clinical suspicion of an FFP were consecutively included. They underwent Spectral CT (GE Revolution 16 cm GSI) upon admission, followed by an MRI. The gold standard for diagnosing FFP is pelvic MRI, showing sensitivity and specificity ranging from 97% to 100%. The acquired images were evaluated and classified using the osteoporotic fractures of the pelvis (OFP) classification. Results: Compared to the reference test, which was the MRI pelvis, the sensitivity of the CT pelvis was determined to be 86.8 (95% confidence interval (CI) 71.9–95.6%) with a specificity of 84.6% (95% CI: 54.6–98.1%, p = 0.453). Spectral CT could identify an additional FFP correctly, exhibiting a sensitivity of 89.5% (95% CI: 75.2–97.1%, p = 0.688), while maintaining the same specificity as the conventional CT. The inter-rater reliability assessment for Spectral CT, conducted by four independent raters, resulted in a Fleiss' Kappa value of 0.516 (95% CI: 0.450–0.582, p < 0.001). Conclusion: The sensitivity of Spectral CT in the detection of pelvic ring fragility fractures shows a slightly lower sensitivity compared to MRI. There were no statistically significant differences observed when compared to conventional CT or MRI. In conclusion, Spectral CT may be beneficial in distinguishing FFP, particularly in cases where a definitive diagnosis is uncertain. Level of Evidence: II. [ABSTRACT FROM AUTHOR]

Reducing methane (CH 4) emissions from the oil and gas (O&G) sector is crucial for mitigating climate change in the near term. MethaneSAT is an upcoming satellite mission designed to monitor basin-wide O&G emissions globally, providing estimates of emission rates and helping identify the underlying processes leading to methane release in the atmosphere. MethaneSAT data will support advocacy and policy efforts by helping to track methane reduction commitments and targets set by countries and industries. Here, we introduce a CH 4 retrieval algorithm for MethaneSAT based on the CO 2 proxy method. We apply the algorithm to observations from the maiden campaign of MethaneAIR, an airborne precursor to the satellite that has similar instrument specifications. The campaign was conducted during winter 2019 and summer 2021 over three major US oil and gas basins. Analysis of MethaneAIR data shows that measurement precision is typically better than 2 % at a 20×20 m 2 pixel resolution, exhibiting no strong dependence on geophysical variables, e.g., surface reflectance. We show that detector focus drifts over the course of each flight, likely due to thermal gradients that develop across the optical bench. The impacts of this drift on retrieved CH 4 can mostly be mitigated by including a parameter that squeezes the laboratory-derived, tabulated instrument spectral response function (ISRF) in the spectral fit. Validation against coincident EM27/SUN retrievals shows that MethaneAIR values are generally within 1 % of the retrievals. MethaneAIR retrievals were also intercompared with retrievals from the TROPOspheric Monitoring Instrument (TROPOMI). We estimate that the mean bias between the instruments is 2.5 ppb, and the latitudinal gradients for the two data sets are in good agreement. We evaluate the accuracy of MethaneAIR estimates of point-source emissions using observations recorded over the Permian Basin, an O&G basin, based on the integrated-mass-enhancement approach coupled with a plume-masking algorithm that uses total variational denoising. We estimate that the median point-source detection threshold is 100–150 kg h -1 at the aircraft's nominal above-surface observation altitude of 12 km. This estimate is based on an ensemble of Weather Research and Forecasting (WRF) large-eddy simulations used to mimic the campaign's conditions, with the threshold for quantification set at approximately twice the detection threshold. Retrievals from repeated basin surveys indicate the presence of both persistent and intermittent sources, and we highlight an example from each case. For the persistent source, we infer emissions from a large O&G processing facility and estimate a leak rate between 1.6 % and 2.1 %, higher than any previously reported emission levels from a facility of its size. We also identify a ruptured pipeline that could increase total basin emissions by 2 % if left unrepaired; this pipeline was discovered 2 weeks before it was found by its operator, highlighting the importance of regular monitoring by future satellite missions. The results showcase MethaneAIR's capability to make highly accurate, precise measurements of methane dry-air mole fractions in the atmosphere, with a fine spatial resolution (∼ 20×20 m 2) mapped over large swaths (∼ 100×100 km 2) in a single flight. The results provide confidence that MethaneSAT can make such measurements at unprecedentedly fine scales from space (∼ 130×400 m 2 pixel size over a target area measuring ∼ 200×200 km 2), thereby delivering quantitative data on basin-wide methane emissions. [ABSTRACT FROM AUTHOR]