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Photonics integrated circuits using Al<sub>x</sub>Ga<sub>1-x</sub>N based UVC light-emitting diodes, photodetectors and waveguides
摘要： We report on a study of UVC photonics integrated circuit (PIC) consisting of monolithically integrated AlxGa1-xN multiple quantum wells (MQWs) based light-emitting diodes, detectors and channel waveguides on sapphire substrates. The waveguide stack consisted of a 1.5 μm thick n-Al0.65Ga0.35N waveguide over an AlN (3.5 μm thick) clad layer. Using the integrated devices, we measured that approximately 80% of the guided-light was confined in the n+-Al0.65Ga0.35N layer, estimated the multi-mode ridge waveguide losses to be 23 cm-1 at λemission~280 nm. We also estimated the multi-mode ridge waveguide losses to be 23 cm-1 at λemission~280 nm. We also measured that approximately 80% of the guided-light was confined in the n+-Al0.65Ga0.35N layer, 7% in the underlying AlN cladding and the remaining 13% in the double-side polished sapphire substrate.
关键词： AlGaN LED,Atomic Layer Deposition,UVC Waveguides,Waveguide Loss,AlGaN Detector,Photonic Integrated Circuit,high Al composition
更新于2025-09-16 10:30:52
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Investigation of characteristics of waveguide channels system formed in PDLC with inhomogeneity of the amplitude-phase distribution of forming field
摘要： This work presents the results of modeling the influence of amplitude, phase and amplitude-phase heterogeneities of the forming field on the spatial distribution of the refractive index profile and, accordingly, the mode composition of radiation capable of propagating in waveguides formed by the holographic method in the photopolymer-liquid crystalline compositions. The spatial distribution of the refractive index is found by solving the system of kinetic equations. The mode composition of the radiation is determined by solving the dispersion equation for TE-modes.
关键词： holographic method,refractive index,waveguide channels,PDLC,mode composition
更新于2025-09-16 10:30:52
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Si-based GeSn photodetectors towards mid-infrared imaging applications
摘要： The GeSn detector offers the high-performance Si-based infrared photodetectors with complementary metal-oxide-semiconductor (CMOS) technique compatibility. In this work, we reports a comprehensive study of Si-based GeSn mid-infrared photodetectors, which includes: i) the demonstration of a set of photoconductors with Sn compositions ranging from 10.5% to 22.3%, showing the cut-off wavelength has been extended to 3.65 μm. The maximum D* of 1.1×1010 cm?Hz1/2?W-1 measured at 77 K is comparable to that of commercial extended-InGaAs detectors; ii) the development of surface passivation technique on photodiode based on in-depth analysis of dark current mechanism, effectively reducing the dark current. Moreover, mid-infrared images were obtained using GeSn photodetectors, showing the comparable image quality with that acquired by using commercial PbSe detectors. This work is a major step towards Si-based mid-infrared photodetectors for imaging applications.
关键词： surface passivation,GeSn photodetector,high Sn composition,imaging,mid-infrared
更新于2025-09-16 10:30:52
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Perovskite quantum dots for light-emitting devices
摘要： Perovskite quantum dots (QDs) have been hotly pursued in recent decades owing to their quantum confinement effect and defect-tolerant nature. Their unique optical properties, such as high photoluminescence quantum yield (PLQY) approaching unity, narrow emission bandwidth, tunable wavelength spanning the entire visible spectrum, and compatibility with flexible/stretchable electronics, render perovskite QDs promising for next-generation solid lighting sources and information displays. Herein, the advances in perovskite QDs and their applications in LEDs are reviewed. Strategies to fabricate efficient perovskite QDs and device configuration, including material composition design, synthetic methods, surface engineering, and device optimization, are investigated and highlighted. Moreover, the main challenges in perovskite QDs of instability and toxicity (lead-based) are identified, while the solutions undertaken with respect to composition engineering, device encapsulation, and lead-replacement QDs are demonstrated. Meanwhile, perspectives for the further development of perovskite QDs and corresponding LEDs are presented.
关键词： device encapsulation,quantum confinement,Perovskite quantum dots,LEDs,instability,composition engineering,flexible electronics,photoluminescence,lead-replacement,stretchable electronics,toxicity,light-emitting devices
更新于2025-09-16 10:30:52
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Data processing for atomic resolution holography
摘要： In photoelectron holography, the intensity of the angular distribution of photoelectrons is measured to obtain a hologram. Thus, a hologram can be defined as a function on a sphere. X-ray fluorescence holography is similar to photoelectron holography. In this study, we describe methods for representing spherical functions that are suitable for atomic resolution holography, and the theory of conversion from the coordinate system of measurement to the various projections. We describe methods for rotational transformations and symmetry operations for atomic resolution hologram and the image composition from measured hologram fragments. In addition, several ways to remove the background from the raw hologram data are discussed.
关键词： atomic resolution holography,photoelectron holography,X-ray fluorescence holography,background removal,spherical functions,symmetry operations,rotational transformations,image composition
更新于2025-09-16 10:30:52
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Determination of the superficial citral content on microparticles: An application of NIR spectroscopy coupled with chemometric tools
摘要： This work evaluates near-infrared (NIR) spectroscopy coupled with chemometric tools for determining the superficial content of citral (????????) on microparticles. To perform this evaluation, using spray drying, citral was encapsulated in a matrix of dextrin using twelve combinations of citral:dextrin ratios (CDR) and inlet air temperatures (IAT). From each treatment, six samples were extracted, and their ???????? and NIR absorption spectral profiles were measured. Then, the spectral profiles, pretreated and randomly divided into modeling and validation datasets, were used to build the following prediction models: principal component analysis-multilinear regression (PCA-MLR), principal component analysis-artificial neural network (PCA-ANN), partial least squares regression (PLSR) and an artificial neural network (ANN). During the validation stage, the models showed ??2 values from 0.73 to 0.96 and a root mean squared error (RMSE) range of [0.061–0.140]. Moreover, when the models were compared, the full and optimized ANN models showed the best fits. According to this study, NIR coupled with chemometric tools has the potential for application in determining ???????? on microparticles, particularly when using ANN models.
关键词： Food composition,Food science,Spectroscopy,Food chemistry,MLR,PCA,PLSR,Prediction,Chemometrics,Food analysis,ANN
更新于2025-09-12 10:27:22
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Combined parametric optimization of P3HT: PC70BM films for efficient bulk-heterojunction solar cells
摘要： In this report, the effects of photoactive blend compositions, film thicknesses, and annealing conditions on the P3HT:PC70BM solar cells performance and reproducibility was investigated. The performance of prepared devices was described by examining their absorption spectra, current-voltage characteristics and external quantum efficiency (EQE). The thickness of active layer was achieved as 190 nm, 125 nm, and 90 nm, by maintaining the spin speed. Current density (Jsc) slightly increases from 6.39 to 7.15 mA/cm2 with increase in thickness from 90 to 125 nm; however, with further increase in film thickness (190 nm), the Jsc was reduced to 4.39 mA/cm2. To optimize the device performance, four different compositions of PC70BM (1:0.6, 1:0.8, 1:1, and 1:12) were investigated at the most favorable film thickness ~ 125 nm. The effect of different PC70BM compositions on photovoltaic performance was demonstrated by X-ray diffraction (XRD) and Raman measurements that illuminated modification in structural properties. Additionally, annealing condition led to achieve the good phase separation for efficient charge separation and transport within P3HT: PCBM film which further leads to increased efficiency (PCE ~ 3.31%). These effects deliver valued facts for the choices of PC70BM amount in P3HT:PC70BM system, and this efficient device optimization might be useful in other efficient photovoltaic systems for better performance through excellent reproducibility.
关键词： P3HT:PC70BM,Composition,Film thickness,Solar cells,Photoactive layer
更新于2025-09-12 10:27:22
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Analysis of the effect of the thermomechanical processing on the laser weld joint of aluminum alloys of Al-Mg-Li and Al-Cu-Li
摘要： The paper presents the experimental investigation of the laser welding of high-strength aluminum-lithium alloys of Al-Cu-Li and Al-Mg-Li system followed by the thermal processing, aimed to the production of a high-strength weld joint. It is founded that the thermal processing (quenching, artificial ageing) of the welded joint increases its strength, however the variation of the microstructure and phase composition is different for the two systems of the alloys. The thermal processing permits getting the tensile strength of the welded sample of 0.9 of the basic alloy strength for Al-Cu-Li and 0.95 for Al-Mg-Li.
关键词： microstructure,thermal processing,CO2 laser,laser welding,phase composition
更新于2025-09-12 10:27:22
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Comparison of Calibration Approaches in Laser-Induced Breakdown Spectroscopy for Proximal Soil Sensing in Precision Agriculture
摘要： The lack of soil data, which are relevant, reliable, a?ordable, immediately available, and su?ciently detailed, is still a signi?cant challenge in precision agriculture. A promising technology for the spatial assessment of the distribution of chemical elements within ?elds, without sample preparation is laser-induced breakdown spectroscopy (LIBS). Its advantages are contrasted by a strong matrix dependence of the LIBS signal which necessitates careful data evaluation. In this work, di?erent calibration approaches for soil LIBS data are presented. The data were obtained from 139 soil samples collected on two neighboring agricultural ?elds in a quaternary landscape of northeast Germany with very variable soils. Reference analysis was carried out by inductively coupled plasma optical emission spectroscopy after wet digestion. The major nutrients Ca and Mg and the minor nutrient Fe were investigated. Three calibration strategies were compared. The ?rst method was based on univariate calibration by standard addition using just one soil sample and applying the derived calibration model to the LIBS data of both ?elds. The second univariate model derived the calibration from the reference analytics of all samples from one ?eld. The prediction is validated by LIBS data of the second ?eld. The third method is a multivariate calibration approach based on partial least squares regression (PLSR). The LIBS spectra of the ?rst ?eld are used for training. Validation was carried out by 20-fold cross-validation using the LIBS data of the ?rst ?eld and independently on the second ?eld data. The second univariate method yielded better calibration and prediction results compared to the ?rst method, since matrix e?ects were better accounted for. PLSR did not strongly improve the prediction in comparison to the second univariate method.
关键词： laser-induced breakdown spectroscopy,soil nutrients,elemental composition,proximal soil sensing,LIBS
更新于2025-09-12 10:27:22
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10% efficiency Cu(In,Ga)Se2 solar cell with strongly (220)/(204) oriented Cu-poor absorber layers sputtered using single quaternary target
摘要： Cu-poor CIGS thin films were fabricated by RF magnetron sputtering from a single quaternary target with the composition of Cu0.7In0.7Ga0.3Se2, in an effort to improve the cell efficiency of CIGS solar cells. The Cu-poor thin films with the ([Cu]/[In]t[Ga]) composition ratios of 0.70e0.77 were obtained showing that the composition of the target can be transferred to the film. It was also observed that the strongly (220)/(204) preferred orientation appeared at the substrate temperatures higher than 600 (cid:2)C, which is known to be essential for achieving high-quality CIGS solar cells. This result indicates that the CueSe compounds present in trace amounts of CIGS films hinder the (112) orientation and promotes the growth of the (220) orientation. As a result, the CIGS absorber layer with the Cu-poor composition and the (220)/(204) preferred orientation exhibited a drastically improved cell efficiency of 10.02%.
关键词： Quaternary single target,CIGS,Cu-poor composition,One-step sputtering
更新于2025-09-12 10:27:22