Search

We report the preliminary demonstration of continuous wave (cw) GaSb-based interband cascade lasers (ICLs) with hybrid cladding layers at high temperatures up to 80 °C near a wavelength of 3.72 μm. These ICLs have narrow-ridge widths of 7–11 μm with improved thermal dissipation compared to broad-area devices. They delivered a cw output power of more than 30 mW/facet at 20 °C and had a cw threshold current density of 270 A/cm2 with a voltage efficiency of 78% at 300 K. The obtained voltage efficiency of 78% is the highest ever reported among cw GaSb-based ICLs at room temperature, indicating an advantage of efficient carrier transport in the ICL with the hybrid cladding layers. The dependence of device performance on the narrow-ridge width and cavity length was investigated. The results suggested ways to further improve future devices. [ABSTRACT FROM AUTHOR]

We exhaustively investigate the temporal correlations between the ultrahigh-frequency (of the order of 1–6 GHz), very high-frequency (of the order of 10–100 MHz), and x-ray (photons with energies from 5 keV to 1 MeV) emissions together with the optical emissions in the near-infrared (within 700–1100 nm) and near-ultraviolet (within 300–400 nm) wavelength regions. The emissions are produced by a laboratory atmospheric discharge developing in an 55 cm air gap at voltages up to 1 MV. When registering various electromagnetic emissions, the discharge current and voltage are measured, as well as nanosecond imaging of the discharge evolution in its own glow is performed. The spatiotemporal localization of the discharge regions associated with the x-ray generation is carried out by employing the group of fast scintillation detectors, and the evolution of plasma structures during the x-ray generation is traced. A chronological map is constructed providing an in-depth understanding of the temporal character and correlations of various electromagnetic emissions. The map allows one to analyze fast ionization processes occurring in the gas-discharge medium and triggering the generation of the corresponding emissions. The generation mechanisms of the considered emissions in an extended high-voltage discharge are discussed. The findings can be helpful in revealing the sources of various electromagnetic emissions accompanying the formation of laboratory and atmospheric discharges. [ABSTRACT FROM AUTHOR]

An ultra-sparse, broadband programmable Active Acoustic Meta-surface (AAMS) that is demonstrated to function as a multi-functional Active Acoustic Meta-device is developed. Functionalities Acoustic Barrier (AB), Acoustic Switch (AS), and Acoustic Transmitter (AT) have been successfully explored. AB functions at a broadband frequency of 455 to 679 Hz as an approximately 100 % acoustic reflector. The functional range of the AS is 425 to 800 Hz, and similarly, the functional range of the AT is 300 to 800 Hz (the full range of the applied frequency sweep). Being a re-configurable device, the AAMS has variable thickness. On a wavelength scale, it varies from 0.10 λ to 0.99 λ for the said functionalities. Here, λ is the wavelength. [ABSTRACT FROM AUTHOR]

Despite rather extensive study of the random lasing effect in ZnO structures, the issue of the optical gain mechanisms in microstructured ZnO random lasers remains poorly understood. In this work, the radiative properties of an array of vertically aligned ZnO microrods, synthesized by a modified thermal evaporation method, were studied. The microrods exhibited lengths up to 60 μm and diameters ranging from 1 to 5 μm. Random lasing from a microrod array was observed in the near-UV range (with a laser emission peak wavelength of ∼391 nm) with a threshold down to 40 kW/cm2 under optical excitation. An analysis of the nature of optical gain in the grown structure was conducted at various temperatures. It was found that at room temperature, two-phonon-assisted exciton recombination is the main process leading to light amplification. [ABSTRACT FROM AUTHOR]

The double-ion chamber (DIC) method has been used to measure photoabsorption cross sections in the ionization region of the sample gas. In this study, we introduce a method to extend the wavelength region of the DIC measurements beyond the ionization threshold wavelength by using the photoion currents from the impurities in the sample gas. To verify this method, the photoabsorption cross sections of C2H2 (ionization threshold wavelength λth = 108.8 nm) have been measured from 105 to 137 nm. The natural impurity, acetone (λth = 127.8 nm), contained 1% in high-purity grade acetylene (C2H2) sample gas, allowing for measurements in the non-ionizing region of C2H2 up to 127.7 nm. By adding 1% benzene (λth = 134.6 nm) in the sample gas, measurements were possible even further, to 134.5 nm. This new method enables the measurement of the photoabsorption cross section by photoions that are produced from the impurities in the sample gas in a substantial amount. The current measurement methodology aligns well with the previous measurements of Suto and Lee [Suto and Lee, J. Chem. Phys. 80, 4824 (1984)]. [ABSTRACT FROM AUTHOR]

Asymmetric quantum wells (AQWs) utilizing interband transitions enhance second-order susceptibility over a wide wavelength range compared to natural crystals. The nonlinear susceptibility is further enhanced in AQWs with type-II band alignment as compared to type-I band alignment, a result of the larger interband charge shift. This enhancement is demonstrated in this work by analyzing three type-I and type-II AQW designs based on the lattice-matched InP/AlGaInAs materials systems using the envelope wavefunction approximation. The calculated interband second-order susceptibility tensor elements in type-II structures range between 20 and 1.60 × 103 pm/V for nearly resonant optical rectification and difference frequency generation applications at near-infrared and terahertz wavelengths, an improvement of nearly 1 order of magnitude over the type-I structures and 1–2 orders of magnitude over natural crystals such as LiNbO3, KTiOPO4 (KTP), or GaAs. A factor of 2–3 further enhancement of the tensor elements is achieved by optimizing the well widths and band offsets of the type-II asymmetric quantum wells. The type-II structure can be implemented in other material systems spanning the longwave infrared to visible wavelengths, enhancing nonlinear susceptibility for various applications, including photonic integrated circuits. [ABSTRACT FROM AUTHOR]

Magic-sized nanocrystals (MSNCs) grow via jumps between very specific sizes. This discrete growth is a possible avenue toward monodisperse nanomaterials that are completely identical in size and shape. In spite of this potential, MSNCs have seen limited study and application due to their poor optical properties. Specifically, MSNCs are limited in their range of emission wavelengths and commonly exhibit poor photoluminescence quantum yields (PLQYs). Here, we report silver doping of CdSe MSNCs as a strategy to improve the optical properties of MSNCs. Silver doping leads to controllable shifts in emission wavelength and significant increases in MSNC PLQYs. These results suggest that doped MSNCs are interesting candidates for displays or luminescent solar concentrators. Finally, we demonstrate that the doping process does not affect the magic size of our MSNCs, allowing further photophysical study of this class of nanomaterial. [ABSTRACT FROM AUTHOR]

Photoluminescence studies in PbS/CdS core/shell nanocrystal thin films reveal that the length of organic ligands at the nanocrystal surface controls the photoluminescence rise time and the short-lived decay component. The long-lived photoluminescence does not depend on the ligand length but strongly depends on the detection wavelength and temperature. We conclude that the observed complex photoluminescence dynamics are governed by a combination of energy transfer and exciton recombination and propose a method to separate these processes. [ABSTRACT FROM AUTHOR]

Rationale: The study of inherent stability characteristics of drugs has been advocated to be important by various regulatory agencies like the ICH, USFDA, and others. The current work was envisaged to investigate the forced degradation profile of the drug ivacaftor under ICH‐prescribed stress conditions, identification of its potential degradants, and postulation of the degradation routes for their generation. Methods: The stress degradation studies were performed on the drug as per the ICH guideline Q1A(R2). A UPLC‐photodiode array‐based chromatographic method was developed to satisfactorily resolve the drug from its degradation products, validated in accordance with various ICH prescribed parameters, and assessed for its BAGI practicality index. The degradation products were identified and characterized by UPLC‐ESI‐QTOF‐MS studies. Results: The drug was found to significantly degrade under conditions of alkaline hydrolytic stress and it was found to be stable under all other stressor environments including acid/neutral hydrolytic, photolytic, thermal, and oxidative stress. Four alkaline hydrolytic degradation products (I‐IV) were revealed by UPLC‐QTOF‐MS studies which were well‐resolved from the drug over a C18 UPLC column by the developed UPLC‐PDA method. The detection wavelength was selected as 310 nm. Characterization of the four degradation products (I–IV) was carried out by their mass spectral data and their respective degradation routes were elucidated. Conclusions: A UPLC‐PDA method was developed and validated for ivacaftor and its practicality BAGI index was computed. Four alkaline hydrolytic degradation products of ivacaftor were revealed through UPLC‐ESI‐QTOF‐MS studies and corresponding degradation routes were elucidated. [ABSTRACT FROM AUTHOR]

The localized surface plasmon resonance metasurface is a research hotspot in the sensing field since it can enhance the light-matter interaction in the nanoscale, but the wavelength sensitivity is far from comparable with that of prism-coupled surface plasmon polariton (SPP). Herein, we propose and demonstrate an ultrasensitive angular interrogation sensor based on the transverse electric mode surface lattice resonance (SLR) mechanism in an all-metal metasurface. In theory, we derive the sensitivity function in detail and emphasize the refraction effect at the air-solution interface, which influences the SLR position and improves the sensitivity performance greatly in the wide-angle. In the measurement, a broadband light source substitutes the single-wavelength laser generally used in traditional angular sensing, and the measured SLR wavelength of broadband illuminant at normal incidence is defined as the single wavelength, avoiding the sensitivity loss from the large angle. The experimental sensitivity can reach 4304.35°/RIU, promoting an order of magnitude compared to those of SPP-sensors. This research provides a novel theory as well as the corresponding crucial approach to achieving ultrasensitive angular sensing. [ABSTRACT FROM AUTHOR]

This paper proposes an optimized spectrum distribution of the input image to significantly enhance the optical efficiency of volume holographic optical element (VHOE)‐based lightguides with exit pupil expansion (EPE). VHOEs‐based lightguides can suppress the eye‐glow effect and use multiplexing to expand field of view (FOV) with good color performance. Along with the demonstration of good image quality, it makes VHOEs one of the best choices for couplers of EPE lightguide. This method utilizes the Model named “Volume Hologram being an Integrator of the Lights Emitted from Elementary Light Sources (VOHIL)” to derive an analytical solution for the wavelength‐angular degeneracy properties of VHOEs, enabling the authors to calculate the peak wavelength distribution that passes through the lightguide. To prove the concept, by meticulously controlling the wavelength distribution and the full width at half maximum of the input light spectrum with a dispersion holographic optical element, a remarkable increase in efficiency is achieved. This approach yields an optical efficiency of 9% for the lightguide with a 30° FOV, representing a 5.63‐fold improvement over conventional VHOE‐based EPE lightguides. It is three times better than the best record of published efficiency in SRG‐based EPE lightguides. This breakthrough has significant potential for advancing the development of high‐performance, user‐friendly near‐eye glasses. [ABSTRACT FROM AUTHOR]

Beam splitter (BS) is an important element for photonic integrated circuits (PICs). Conventional BSs designed by traditional approaches are too large to be suitable for PICs. An inverse design method which combines the adjoint method with the finite-difference frequency-domain method (FDFD) and the finite-difference time-domain method (FDTD) is proposed, in which the adjoint method is adopted to construct the structures while the FDFD is used to simulate the fields of the structures at the target wavelength, and the FDTD is used to study their fields and spectra at a wider wavelength range. And a series of compact Si-based arbitrary ratio power splitters (ARPSs) with splitting ratios (SRs) ranging from 1:1 to 10:1 on 2.5 μ m × 2.5 μ m substrates have been designed by this method. Their SRs fully match the design expectation accurately with total transmission efficiencies of more than 90% at the target wavelength of 1550 nm. Multi-channels BSs with 3:4:1 and 4:1:3:2 SRs have been designed by this method as well, and have good performance with footprints of 2.5 μ m × 2.5 μ m and 3.2 μ m × 3.2 μ m, respectively. Furthermore, the Si3N4-based ARPSs with footprints of 3.0 μ m × 4.0 μ m have been designed, and their performance met expectations also. The results of 2:1 and 3:1 Si3N4-based ARPSs have been shown that total transmission efficiencies are 88.14% and 91.48% at the center wavelength of 1400 nm. Benefiting from the high speed of FDFD, this method has high optimization efficiency. And all the results simulated by FDTD agree well with FDFD. It provides a robust means to construct compact ARPSs and other nanophotonic devices. [ABSTRACT FROM AUTHOR]

Metalens is a cutting-edge optical marvel, revolutionizes a plethora of applications like cameras, telescope, augmented reality (AR) and virtual reality (VR). Despite having ultrathin structure, lightweight nature, and multifunctionality, achievement of both achromatic imaging and wide field of view (WFOV) remains a persistent challenge. To address these concerns, here we present a novel approach using a harmonic metalens featuring a quadratic phase profile to achieve achromatic behavior and WFOV simultaneously. This innovation enables WFOV imaging using the Fourier transform of quadratic phase profile and achromatic behavior at RGB wavelengths (blue λ = 488 nm, green λ = 532 nm and red λ = 633 nm) with a WFOV of up to ± 45 ∘ . The designed harmonic metalens is polarization-insensitive, with a numerical aperture of 0.79, and it achieves a maximum focusing efficiency of ∼50% at a wavelength of 633 nm under normal incidence. Being polarization insensitive and achromatic, proposed scheme will certainly broaden the utilization of metalenses in AR/VR, displays and applications in imaging. © 2024 Optical Society of America. [ABSTRACT FROM AUTHOR]

This paper presents a numerical modeling approach to analyze the dynamic response of gravity anchors subjected to waves at various submergence depths. The aim is to model stages of lowering during the installation process of offshore wind energy installations. The study includes an investigation of the effect of different outer shapes of the gravity anchor to understand the influence on the dynamic response of the anchor. The results demonstrate that the submergence depth has a significant impact on the stability of the anchor during the lowering process, particularly at the initial lowering phase, resulting in higher wave-induced forces and increased risks of instability. With the use of streamlined anchor shapes, compared with the results for the baseline anchor, a reduction of 20.9% and 16.6% in heave, 47.8% and 45.8% in pitch, and 73.4% and 75.3% in surge motions are observed for C- and V-shaped anchors, respectively. When comparing the influence of different wave parameters, compared with the wave height, the wavelength is shown to drive undesirable anchor dynamic motions. [ABSTRACT FROM AUTHOR]

Aggregation‐induced emission (AIE) carbon dot (CDs) in solid state with tunable multicolor emissions have sparked significant interest in multidimensional anti‐counterfeiting. However, the realization of solid‐state fluorescence (SSF) by AIE effect and the regulation of fluorescence wavelength in solid state is a great challenge. In order to solve this dilemma, the AIE method to prepare multi‐color solid‐state CDs with fluorescence wavelengths ranging from bright blue to red emission is employed. Specifically, by using thiosalicylic acid and carbonyl hydrazine as precursors, the fluorescence wavelength can be accurately adjusted by varying the reaction temperature from 150 to 230 °C or changing the molar ratio of the precursors from 1:1 to 1:2. Structural analysis and theoretical calculations consistently indicate that increasing the sp2 domains or doping with graphite nitrogen both cause a redshift in the fluorescence wavelength of CDs in the solid state. Moreover, with the multi‐dimensional and adjustable fluorescence wavelength, the application of AIE CDs in the fields of multi‐anti‐counterfeiting encryption, ink printing, and screen printing is demonstrated. All in all, this work opens up a new way for preparing solid‐state multi‐color CDs using AIE effect, and further proposes an innovative strategy for controlling fluorescence wavelengths. [ABSTRACT FROM AUTHOR]

A high‐capacity lithium‐niobate‐on‐insulator (LNOI) optical transmitter for next‐generation passive optical‐networks (PONs) is proposed and demonstrated with ultra‐low temperature‐dependence for the first time by simultaneously introducing Z‐ and Y‐propagation LNOI photonic waveguides. There are five wavelength‐division‐multiplexed channels involved with the center wavelengths of 1270/1300/1342/1537/1577 nm, and the photonic filters are realized by integrating amplitude‐apodized multimode waveguide gratings (MWGs) and mode (de)multiplexers designed with Z‐propagation LNOI photonic waveguides, which are found to be with a low thermo‐optic coefficient and thus enable the athermalization. Meanwhile, high‐speed optical modulators connected at the add ports of the photonic filters for the 1342/1577 nm channels are developed with Y‐propagation LNOI photonic waveguides with the maximal electro‐optic effect. For the fabricated on‐chip optical transmitter, box‐like spectral responses are achieved with ultra‐low excess losses of <0.5 dB and low inter‐channel crosstalk of < −26 dB for all the channels whose bandwidths are respectively ∼16/20/4/15/5 nm as expected. The present LNOI photonic chip is nearly athermal, exhibiting very low temperature‐dependence less than 8.7 pm/°C in the full wavelength range of >300 nm. Finally, high‐capacity data transmissions of 50/100 Gbps on‐off‐keying signals and 100/200 Gbps four‐level‐pulse‐amplitude‐modulated signals are demonstrated, providing a promising solution for next‐generation PONs. [ABSTRACT FROM AUTHOR]

We investigated how the positional arrangement of electron-donating (amino) and electron-withdrawing (ester) groups in single benzene-based fluorophores influences their emission properties. By synthesizing 26 regioisomeric fluorophores, we achieved wavelength modulation from 322 to 539 nm, revealing key correlations between functional group positioning and photophysical behavior. [ABSTRACT FROM AUTHOR]

A simple and efficient method was developed to prepare the novel fluorescent tetra‐substituted thiophene derivatives. This method involves using the Gewald's conditions, followed by the Vilsmeier–Haack–Arnold (VHA) formylation. By judiciously controlling the use of the VHA reagent, we have selectively introduced a formyl group into position 5 of the thiophene. This had a direct impact on its fluorescence properties. The resulting compounds have showed an intense fluorescence in the emission wavelength range of 420–500 nm with a 10−6 M concentration. All new products have been structurally confirmed by spectroscopic data. The structure of compound 2g was confirmed by single‐crystal X‐ray diffraction. [ABSTRACT FROM AUTHOR]

Germanate ceramics Li2ZnGeO4:Nd3+ and Li2MgGeO4:Nd3+ have been studied for near‐infrared (IR) luminescence applications. The phase identification showed that both ceramic compounds crystallized in a monoclinic lattice, characteristic of a broad family of germanate olivines. Near‐IR luminescence spectra have been analyzed for Li2AGeO4:Nd3+ (A = Zn, Mg) under different excitation wavelengths. Near‐IR emission bands observed in the second biological window correspond to the ceramic host as well as 4F3/2 → 4I11/2 and 4F3/2 → 4I13/2 transitions of Nd3+ ions, respectively. Based on luminescence spectra and their decays, several spectroscopic parameters for un‐doped and Nd3+‐doped ceramic samples were determined. The experimental results for germanate olivines containing Nd3+ ions suggest that ceramic host gives important contribution to near‐IR luminescence at second biological window. [ABSTRACT FROM AUTHOR]

The increasing demand for extracting comprehensive information from light through multispectral and polarization imaging has driven the development of advanced photodetection technologies. In response, a polarization‐sensitive narrowband InGaAs photodetector (PD) operating in the short‐wave infrared (SWIR) range is proposed, capable of capturing wavelength, intensity, and polarization data concurrently without additional optical components. The device is formed by integrating an InGaAs PD onto a silicon grating, utilizing the guided‐mode resonance (GMR) effect to amplify absorption at specific target wavelengths. The intrinsic polarization dependence of the 1D GMR structure allows for distinct absorption peaks for TE and TM polarized light. The detection performance of the device, including spectral rejection ratios greater than 30, peak responsivities of 0.46 A W−1, and polarization extinction ratios of up to 41.3 is demonstrated. Precise design of the period and arrangement of the grating enables fabrication of pixel arrays with diverse detection wavelengths and polarization directions, in a single process eliminating the process complexity. This is the only capability of this study among previously reported devices. [ABSTRACT FROM AUTHOR]

Background and objectives: Laser skin therapy and intense pulsed light (IPL) therapy are both light-based treatments used for various skin concerns. They have been used since decades and each system have their own specificity, advantages, and drawbacks. However specific treatment is still not accessible with standard techniques due to difficulties having a source with both laser and IPL advantages. We describe a new concept, the fibered luminescent concentrator—FLC, based on luminescent concentrators capable of concentrating spectrally and spatially an IPL source, resulting in a multi-color fibered device. Study design/materials and methods: The FLC utilizes luminescent materials arranged in parallelepiped shapes polished on all faces. The IPL broadband spectrum is absorbed by the luminescent molecules and is re-emitted to a red shifted wavelength. The emitted spectral bandwidth ranges from green to dark red, depending on the type of luminescent concentrator. This light is then spatially concentrated by total internal reflections in the parallelepiped and guided through a fiber to the final operator. Results: We have developed three different solid luminescent concentrators based on a transparent polymer sheet (PMMA) doped with luminescent organic dye molecules for yellow and red emission, and an alexandrite crystal for emission in the dark red spectrum. We demonstrate that our new non-laser FLC device can concentrate spectrally and spatially the light with no temporal deformation and offers real opportunities for treatments where the IPL is less well-adapted. Conclusion: The FLC is an additional tool for existing conventional systems such as laser or IPL sources. It is easily adaptable to any IPL source and is a very good complement, especially for wavelengths where the laser cannot easily produce light, such as the yellow band. [ABSTRACT FROM AUTHOR]

Efficient light coupling into the fiber waveguides is important in numerous applications, while the low in‐coupling coefficients of commercially available step‐index fibers significantly narrow their application domains. It is recently introduced that well‐defined periodic nanostructures, such as annulus gratings, allow to substantially boost in‐coupling coefficients. In this study, the genetic algorithm is applied for the optimization of trapezoidal polymer gratings. The experimental data showcase multiply enhanced light coupling at preselected incident angles with respect to a bare fiber. As a breakthrough result, the development of an axial‐asymmetric four‐sector grating, reaching the percentage level of light coupling efficiency in a broad angular range from 0∘$^{\circ }$ to 70∘$^{\circ }$ that outperforms axial‐symmetric gratings by about order of magnitude. Further, the high average light coupling efficiency is verified in the finite angular intervals at multiple wavelengths of 650, 1000, and 1550 nm. This solution highlights the enhancement of algorithm‐designed structures axially‐asymmetric systems for fiber‐based highly efficient light collections, that will further benefit extensive applications such as wide‐field endoscopies. [ABSTRACT FROM AUTHOR]

The coordination structure of Sb3+ within the host lattice critically influences its photophysical properties, sparking interest in luminescent metal halides with multiexciton emissions. Furthermore, the multi‐coordination lattice structure of Sb3+ dynamically emits light with excitation wavelength, highlighting the potential of Sb3+ ions in tuning luminescence and developing advanced optoelectronic materials. Herein, Sb3+ ions are successfully doped into Cs2SnCl6, and the obvious excitation wavelength‐dependent emission of Cs2SnCl6: Sb at room temperature is observed. To explain this phenomenon, density functional theory (DFT) calculations and time‐resolved spectra are conducted to confirm that the emission originated from two luminescence centers associated with the [SbCl6]3− and [SbCl5]2− coordination. Based on the tunable emission of Cs2SnCl6: Sb and the effective electron transfer between two triplet self‐trapped exciton states induced by Bi3+ and Sb3+, a pixelated code for information encryption is designed. The encoded patterns exhibit color changes under different UV wavelengths, enabling secure and straightforward information encryption. Furthermore, a sensitive UV wavelength sensor is prepared based on Cs2SnCl6: Bi/Sb, exploiting the monotonic relationship between chromaticity coordinates and wavelength, achieving a resolution superior to previously reported wavelength sensors. This study marks a substantial step toward advancing the multifunctional application of lead‐free metal halides. [ABSTRACT FROM AUTHOR]

The nonlinear refractive index of large area monolayer molybdenum disulfide (MoS2) thin film at the 1,550 nm wavelength band is determined using time-resolved z-scan technique. MoS2 exhibits positive nonlinear phase shift with a large nonlinear refractive index, n 2 value of 1. 4 0 × 1 0 − 1 3 m 2 W − 1 . The obtained value is similar to the n 2 value of monolayer MoS2 film measured at 2.0 μ m, and is approximately five and seven orders of magnitude larger than silicon and common bulk dielectrics. The large n 2 indicates that MoS2 can be used as nonlinear refractive 2D material for photonics applications operating in the 1,550 nm optical telecommunications wavelength band. [ABSTRACT FROM AUTHOR]

Rail corrugation intensifies wheel–rail vibrations, often leading to damage in vehicle–track system components within affected sections. This paper proposes a novel method for identifying rail corrugation, which combines Complete Ensemble Empirical Mode Decomposition with Adaptive Noise (CEEMDAN), permutation entropy (PE), and Smoothed Pseudo Wigner–Ville Distribution (SPWVD). Initially, vertical acceleration data from the axle box are decomposed using CEEMDAN to extract intrinsic mode functions (IMFs) with distinct frequencies. PE is used to evaluate the randomness of each IMF component, discarding those with high permutation entropy values. Subsequently, correlation analysis is performed on the retained IMFs to identify the component most strongly correlated with the original signal. The selected component is subjected to SPWVD time–frequency analysis to identify the location and wavelength of the corrugation occurrence. Filtering is applied to the IMF based on the frequency concentration observed in the time–frequency analysis results. Then, frequency–domain integration is performed to estimate the rail's corrugation depth. Finally, the algorithm is validated and analyzed using both simulated data and measured data. Validation results show that this approach reliably identifies the wavelength and depth characteristics of rail corrugation. Additionally, the time–frequency analysis results reveal variations in the severity of corrugation damage at different locations. [ABSTRACT FROM AUTHOR]

Recently, steel girders with sinusoidal corrugations have become increasingly popular compared to those with traditional flat webs. This paper presents the second part of the research on the application of corrugated plates with different sinusoidal profiles as webs in girders. Parametric studies have been carried out in both linear and nonlinear domains, based on a representative numerical model developed and validated by experimental results. The research focused on the influence of the sinusoidal shape of the web on the shear capacity of the girders and the ultimate failure mode. The analyses were carried out using Abaqus software. Based on the results of the numerical analyses, it was concluded that increasing the wavelength of the sinusoidal wave decreases the ultimate shear capacity of the girders. This parameter also influences the failure mode. The results show that the wave amplitude has a small effect on the critical capacity. However, the amplitude influences the increase in the post-critical load and the size of the plastic zones located in the webs during the final phase of failure. With regard to the geometric parameters of the web, it was found that increasing the web thickness significantly improves the performance of the girders, while the web height has a negligible effect. It was also shown that the design guidelines in Eurocode 3 are very conservative in terms of estimating the shear buckling capacity of beams with sinusoidal corrugated webs and significantly underestimate the values. [ABSTRACT FROM AUTHOR]

An in situ and nondestructive technique is developed to image the formation and evolution of dark line defects in the cavity of a high-power diode laser. The technique uses broadband near infrared emission that originates in the laser's core layers and enables defects to be imaged with high spatial resolution through the substrate. In particular, it enables defect imaging through the substrate of shorter wavelength lasers, even when the substrate is opaque near the lasing wavelength. The evolution of dark line defects during aging is studied in several devices, with correlations established between the observed characteristics of defect growth and changes in device parameters such as optical power, operating wavelength, threshold current, and slope efficiency. Gradual degradation is found to be associated with dark line defects that slowly propagate from dark spots that are present in the device interior in its fresh (unaged) condition, rather than propagating from spots that are formed during aging, suggesting a strategy to screen fresh devices for expected reliability. This defect growth phenomenon is found to be particularly evident in the dark spots near the output facet. [ABSTRACT FROM AUTHOR]

Accurate assessment of food freshness is critical to maintaining human health. However, the complex environment of food usually leads to false‐positive measurements result. Therefore, the development of sensing platforms with self‐calibration for accurate detection of food freshness in complex environments is essential. Here, using the green fluorescence‐emitting FITC‐ene and the red fluorescence‐emitting DBA‐ene‐Eu3+ as fluorescent units, fluorescent polymeric materials P1‐P4 with excitation wavelength‐dependent (254 and 365 nm, matched with standard UV lamp) emission are prepared. P1‐P4 responded rapidly to biogenic amines (BAs). Among them, P3 exhibits the widest linear range, and the most noticeable fluorescence color change (from orange‐red to yellow‐green) under 254 nm excitation and enhanced green fluorescence under 365 nm excitation. The changes of P3‐prepared labels at different excitation wavelengths can be utilized to rapidly evaluate the food's freshness. Furthermore, by using a smartphone to read the Red/Green/Blue values of the labels, the total volatile basic nitrogen (TVBN) values can be output to quantitatively evaluate the food freshness, and the output TVBN values at different excitation wavelengths are utilized for mutual calibration to improve the accuracy of the estimation results. This self‐calibrating sensing platform is fast and nondestructive, which provides an effective method for the accurate evaluation of food freshness. [ABSTRACT FROM AUTHOR]

Finding birefringent material with giant optical anisotropy is urgent for photonic applications. However, the application of existing birefringent materials is limited by restricted transparency wavelength or optical anisotropy. The process of trial and error is time‐consuming and inefficient in terms of resources, especially when compared to the vast design spaces for materials. The immense chemical space necessitates a high‐throughput approach for giant optical anisotropy materials design. Here, a full‐applied wavelength map of birefringent materials is constructed, from conventional visible expanding to ultraviolet and deep‐ultraviolet region by high‐throughput screening methods. And highlighted 579 materials birefringence exceeds the one of available commercial birefringent materials in corresponding regions. Significantly, 54 materials possess giant birefringence above 0.5 @1064 nm. Via developing a high‐throughput screening technique for microscopic structures with given coordination number, the study further characterizes a comprehensive map of functional modules featuring birefringent activeness. According to the macroscopic and microscopic dual‐functional maps, and a novel crystal Li2(HC3N3S3)∙5H2O with birefringence difference 0.532 @546 nm is designed and synthesized successfully. This study identifies desired materials with high performance in unheeded chemical spaces. [ABSTRACT FROM AUTHOR]

Photodetectors play a pivotal role in modern technology, particularly in applications requiring precise light detection and imaging. Traditional photodetectors, however, are often constrained by their fixed wavelength ranges, making them inadequate for multi-band detection needs. To address this limitation, phase change materials (PCMs) have emerged as a promising solution. PCMs are notable for their high sensitivity, rapid response times, and their capacity to detect a broad spectrum of wavelengths. These materials can transition between crystalline and amorphous states, allowing real-time adjustment of the detection wavelength. Furthermore, integrating surface plasmon resonance with photodetectors significantly enhances their performance by boosting light absorption and signal strength. This review delves into the fundamental principles, benefits, and challenges of various types of photodetectors. It specifically highlights traditional photodetectors, plasmon-enhanced photodetectors, and recent advancements in PCM-based photodetectors. By examining these innovations, we aim to provide valuable insights that could shape the future development and application of photodetector technology, ensuring they meet the evolving demands of various technological fields. [ABSTRACT FROM AUTHOR]

Featured Application: This study contributes to the timely detection of track defects, helping to prevent safety incidents during train operations. Railway turnout is a critical railway infrastructure that guides trains in switching tracks. Over time, uneven rail wear can lead to switch rail reduction value (SRRV) deviation, a typical structural defect that compromises turnout functionality and jeopardizes train operation safety. Current SRRV deviation detection methods rely primarily on inefficient manual inspections, making it difficult to ensure operational safety. To address this issue, the study carried out a comprehensive investigation combining numerical and experimental analyses. First, a rigid–flexible coupled dynamics model of a vehicle-turnout system was developed to analyze the wheel–rail dynamic interaction forces and contact relationships under various SRRV deviation conditions. The results revealed that SRRV deviation significantly affects both wheel–rail interaction forces and the turnout structural irregularity wavelength. Thus, based on discrete wavelet transform (DWT), a wheel–rail force trend component was derived that can effectively analyze the turnout structural irregular wavelength, and the mapping relationship between SRRV deviation and the wheel–rail force trend component was then established. Finally, an efficient and accurate method for identifying SRRV deviation based on wheel–rail force trend component was proposed and validated using field-measured data from trains passing through turnouts. This study contributes to the timely detection of track defects, helping to prevent safety incidents during train operations. [ABSTRACT FROM AUTHOR]

This article introduces an inscribed hexagonal-slot square patch antenna developed in the field of RFID technology for reader applications. The proposed structure is energized with one feeding element. This study proposes a high-gain microstrip antenna for ISM band applications at 5.8 GHz. FR4 material is utilized in the design and fabrication of the antenna. The resulting design achieves a -10 dB impedance bandwidth of around 3.6% in the ISM band. The proposed design is compact in comparison to several contemporary designs and has dimensions of 0.43λ × 0.43λ × 0.03λ (λ = wavelength at 5.8 GHz). The measurement reveals that the antenna can operate across the frequency band 5.67 GHz-5.88 GHz having a maximum gain value of 4.58 dBi at 5.77 GHz. The satisfaction of the propagation test in different environments and the reading distance value of 2.81 cm at the ISM band supports the application of the structure as a short-range RFID reader. [ABSTRACT FROM AUTHOR]

Position‐sensitive detectors (PSDs) are widely used in optical inspection applications, such as precise measurement of distance and angle, surface profiling, and motion tracking, etc. The lateral photovoltaic effect is the mechanism employed by most PSDs to determine position, but its gain‐free nature hinders weak‐light detection and applications. Here, a new position recognition mechanism with an intrinsic high gain is proposed and employ it to design a weak‐light and large‐size photoconductor‐type PSD. The position recognition is established by the intrinsic link between the gain and channel length in a photoconductor, and the designed linear correlation between the channel length and position. The photoconductor‐type graphene/Si PSD based on the recognition mechanism shows an active length of over 1 mm, a high spatial position resolution at the sub‐micrometer level, and a low detection limit power of 100 pW. Compared with Si PSDs, the gain of the photoconductor‐type PSD is improved by 3–4 orders of magnitude. In addition, the operational wavelength range of the PSD is expanded to include the near‐infrared region, specifically at 1300 and 1550 nm. The new position recognition mechanism paves the way for the development of ultra‐sensitive light position detection. [ABSTRACT FROM AUTHOR]

Metasurfaces garner widespread attention for their remarkable ability to precisely manipulate light and construct optical multiplexing devices. However, there is still a lack of effective solutions for achieving high‐performance wavelength decoupling in the realm of wavelength multiplexing. In this work, a novel wavelength decoupling method based on minimalist metasurfaces featuring a single‐celled configuration is proposed. These metasurfaces are composed of only two types of nanobricks, each capable of modulating the phase of two different wavelengths simultaneously as desired. The proposed minimalist metasurfaces possess the advantages of flexible design, enabling wavelength decoupling with incidences at both co‐ and cross‐polarization states. Interestingly, by integrating the wavelength decoupling metasurface with liquid crystal devices, information encryption can be achieved. The proposed wavelength decoupling method holds broad application prospects in the fields of optical data storage, image display, information security, and beyond. [ABSTRACT FROM AUTHOR]

Single‐pixel imaging technology can capture images at wavelengths outside the reach of conventional focal plane array detectors. However, the limited image quality and lengthy computational times for iterative reconstruction still hinder its practical application. Recently, single‐pixel imaging based on deep learning has attracted a lot of attention due to its exceptional reconstruction quality and fast reconstruction speed. In this review, an overview of the current status, and the latest advancements of deep learning technologies in the field of single‐pixel imaging are provided. Initially, the fundamental principles of single‐pixel imaging and deep learning, followed by a discussion of their integration and associated benefits are presented. Subsequently, a comprehensive review is conducted on the advancements of deep learning in various domains of single‐pixel imaging, covering super‐resolution single‐pixel imaging, single‐pixel imaging through scattering media, photon‐level single‐pixel imaging, optical encryption based on single‐pixel imaging, color single‐pixel imaging, and image‐free sensing. Finally, open challenges and potential solutions are discussed. [ABSTRACT FROM AUTHOR]

The excellent anti-interference ability of near-infrared (NIR) fluorescent materials derived from long-wavelength emission has made them one of the most fascinating fluorescence probes. In this work, gold nanoclusters stabilized with glutathione (GSH-AuNCs) were prepared and exhibited excellent NIR fluorescence at 806 nm, indicating their potential as excellent fluorescence probes. It is gratifying that S2− could be sensitively and rapidly recognized through the "turn-off" strategy of NIR fluorescence of AuNCs. It is speculated that the quenching was due to the aggregation-caused quenching (ACQ) phenomenon. The combination of a longer wavelength emission of 806 nm and the strong binding ability of Au and S endowed the constructed sensing system with outstanding sensitivity and selectivity. A good linear relationship for the detection of S2− was obtained in the range of 0–23.75 μM, with a limit of detection (LOD) of 14.67 nM (S/N = 3). This NIR fluorescence probe was successfully used for the detection of S2− in real samples with satisfactory results. [ABSTRACT FROM AUTHOR]

AbstractAs a key component of lightweight impact-protection devices, thin-walled structures with marvelous specific energy absorption (SEA) have attracted wide attention. Inspired by leaf venation in royal water lily, a hybrid multi-cell thin-walled structure with fractal and hierarchy architectures is proposed. Its crashworthiness is compared with traditional cylinder by combining finite element simulation and experiment, and corresponding mechanism is revealed. The results show that due to more folds and smaller folded wavelength, the venation-like structure exhibits better crashworthiness than the cylinder. Increasing the initial bifurcation number and hierarchy level of venation-like structure will introduce massive corner constraints, especially the hierarchy level, which benefits folding deformation and improving effectively crashworthiness. Further, a fully hybrid venation-like structure is designed by introducing gradient architecture. With the increase of length-gradient or thickness-gradient, the SEA first linearly increases and then slightly decreases. Under the optimal length-gradient, majority of area exhibits high internal energy. By taking the gradient length and thickness simultaneously, a kind of hybrid deformation mode with quasi-uniform small folding and overall large folding appears, where multiple small folds interacts strongly, achieving good load-bearing capacity. The optimal SEA of venation-like structure is 81.5% higher than that of the cylinder. [ABSTRACT FROM AUTHOR]

The early evolution of the traveling crossflow instability on a flat plate with a sweep angle of 75° is experimentally investigated. The experiments are conducted in a Mach 6 quiet wind tunnel through the nano-tracer-based planar laser scattering (NPLS) technique under the unit Reynolds number of 3.45 × 106 m−1. The spanwise and streamwise structures of the traveling crossflow waves are captured, and the wavelength and frequency characteristics of the traveling crossflow waves are quantitatively analyzed based on wavelet analysis. The results show that with the increase in z-coordinate and x-coordinate, the distribution range of the traveling crossflow waves in y-direction expands, the amplitude of disturbance waves increases, and saturated crossflow wave structures appear gradually. The wavelength of the crossflow waves is about 24 mm and does not change much in different positions. In addition, the propagation velocity of the crossflow waves along the x-direction at the position of x = 130 mm and z = 60 mm is quantitatively calculated, U = 303 m/s. Thus, the characteristic frequency of the crossflow waves obtained from the NPLS image is f ≈ 12 kHz, close to 9.57 kHz measured by Kulite at the same position. [ABSTRACT FROM AUTHOR]

The Richtmyer–Meshkov instability of a light fluid layer with two different interface modes is studied numerically. By fixing the wavelength of the second interface (I2) while varying that of the first interface (I1), we examine distinct cases with identical wavelengths at both interfaces, as well as smaller or larger wavelengths at I1, to explore the effects of initial layer configurations on instability development. The larger wavelength interface significantly transmits modes to the smaller wavelength interface, whereas mode transmission in the reverse direction is limited. This results in two primary consequences: (i) the smaller wavelength interface and the overall mixing layer evolve periodically with the larger wavelength; (ii) compared to the identical wavelength case, the linear amplitude growth duration of I2 is slightly extended for the smaller I1 wavelength case, but significantly prolonged for the larger I1 wavelength case. The linear amplitude growth rate of I2 for all cases can be predicted by the model of Jacobs e t a l. [ J. Fluid Mech. , vol. 195, 23–42 (1995)]. For cases with identical wavelengths and larger I1 wavelengths, the collisions of finger structures at both interfaces occur earlier, suppressing the growth of mixing width at early times while enhancing the mixed mass. In the later stages, the overall mixing efficiency in these cases significantly declines, despite continuous increases in both mixing width and mixed mass. This decline is attributed to severe deformation of the mixing layer due to interactions between finger structures, confining intense mixing to localized regions. [ABSTRACT FROM AUTHOR]

Binocular vision may serve as a good model for research on awareness. Binocular summation (BS) can be defined as the superiority of binocular over monocular visual performance. Early studies of BS found an improvement of a factor of about 1.4 (empirically), leading to models suggesting a quadratic summation of the two monocular inputs (√2). Neural interaction modulates a target's visibility within the same eye or between eyes (facilitation or suppression). Recent results indicated that at a closely flanked stimulus, BS is characterized by instability; it relies on the specific order in which the stimulus condition is displayed. Otherwise, BS is stable. These results were revealed in experiments where the tested eye was open, whereas the other eye was occluded (mono-optic glasses, blocked presentation); thus, the participants were aware of the tested eye. Therefore, in this study, we repeated the same experiments but utilized stereoscopic glasses (intermixed at random presentation) to control the monocular and binocular vision, thus potentially eliminating awareness of the tested condition. The stimuli consisted of a central vertically oriented Gabor target and high-contrast Gabor flankers positioned in two configurations (orthogonal or collinear) with target–flanker separations of either two or three wavelengths (λ), presented at four different presentation times (40, 80, 120, and 200 ms). The results indicate that when utilizing stereoscopic glasses and mixing the testing conditions, the BS is normal, raising the possibility that awareness may be involved. [ABSTRACT FROM AUTHOR]

Palladium (Pd) nanocubes, a type of metallic nanostructure, have demonstrated remarkable optoelectronic properties, garnering significant attention. However, their nonlinear optical characteristics and related device applications remain underexplored. In this study, we report the fabrication of a novel saturable absorber (SA) by depositing Pd nanocubes onto a D-shaped fiber (DF). The Pd nanocubes, with an average size of 12 nm, were synthesized and integrated with a DF, resulting in a highly robust SA with broadband saturable absorption characteristics. When incorporated into Er3+-doped laser cavities, the Pd-DF SA enabled the generation of ultrafast pulses with a central wavelength of 1560 nm, a corresponding repetition rate of 26.7 MHz, and a temporal width of 1.85 ps. Our findings highlight the strong potential of the Pd-DF device as a versatile SA for constructing high-energy ultrafast fiber lasers. [ABSTRACT FROM AUTHOR]

Amplified spontaneous emission of CdTe and CdTe-Ag quantum dot composites were compared for increasing the optical stripe length, whereby optical gain coefficients for various emission wavelengths were obtained. In the case of CdTe-Ag nanoparticle composites, we observed that plasmonic coupling causes both optical enhancement and quenching at different wavelengths, where the amplified spontaneous emission intensity becomes enhanced at short wavelengths but suppressed at long wavelengths (>600 nm). To analyze the logistic stripe length dependence of amplified spontaneous emission intensity, we used a differential method to obtain the gain coefficient beyond the amplification range. This analysis enabled us to find the limit of the commonly used fitting method in terms of a threshold length and a saturation length, where amplification begins and saturation ends, respectively. [ABSTRACT FROM AUTHOR]

This study aimed to explore the impact of three wavelength-cut (TWC) lenses, which allowed 75% luminance transmittance while blocking wavelengths < 420 nm, approximately 460 nm, and approximately 585 nm, on visual function and color perception, and aging interaction effect. This single-center study enrolled 30 participants into two groups including 15 young participants (age 21.4 ± 1.3 years) and 15 older participants (age 71.7 ± 1.7 years). We used TWC lenses and a neutral density (ND) filter to assess the wavelength-cut effects on visual acuity, contrast sensitivity, and cone contrast sensitivity. Visual acuity and contrast sensitivity were assessed under photopic (luminance 85–100 cd/m2) and mesopic conditions (luminance 0.8 cd/m2). Significant interactions between age and lens conditions were observed for contrast sensitivity under photopic conditions (Bonferroni corrected α = 0.025, F(1,28) = 7.98, P = 0.01, η2 = 0.003), suggesting that contrast sensitivity to white and black gratings is better with TWC lenses (75%) than with the ND filter in young participants (F(1,28) = 7.25, P = 0.01, η2 = 0.206). However, the lens condition did not affect visual acuity and had only a minimal effect on cone contrast sensitivity for each cone type. In conclusion, TWC lenses, despite their nearly colorless and transparent appearance, can selectively block specific wavelengths to improve contrast sensitivity, while minimally affecting color perception. However, since the effect size of these interactions is very small, the impact is limited, therefore glasses should be prescribed with caution for young individuals. [ABSTRACT FROM AUTHOR]

In this paper, a parallel polarization-beam-splitter-based fiber optic filter with adjustable channel spacing is proposed and demonstrated. The transmission characteristics of the proposed filter are simulated and analyzed using the transmission matrix theory. Simulation results show that the filter can generate three different channel spacings by adjusting different polarization controllers (PCs) in front of the polarization beam splitter (PBS). The experiment confirms the feasibility of a multi-wavelength fiber laser (MWFL) constructed based on this filter in achieving channel spacing switching. Its wavelength spacing can be switched between 0.46 nm, 0.66 nm, and 0.88 nm, matching the simulated results of the filter. The power fluctuations between the outputs of the three-channel spacing outputs are less than 1.17 dB, 0.89 dB, and 0.98 dB, and the wavelength fluctuations are less than 0.18 nm, 0.14 nm, and 0.13 nm, respectively. [ABSTRACT FROM AUTHOR]

We develop a multilayer model to study roll waves in mudflow of Herschel–Bulkley fluids initiated by periodic and localized disturbance. Simulations are conducted of the temporal development of periodic roll waves and spatial development of wave packets due to localized disturbance. The results of the temporal development are expressed in terms of the power-law index, the relative plug-layer thickness, the Froude number, and the perturbation wavelength. Our simulation for the spatial development shows the roll waves led by a dominant front runner and followed by a quiescent tail, closely reproducing a well-known river-clogging phenomenon of the natural mudflow observed in the mountain rivers on mild slopes. The leading wave of the roll-wave packet, i.e., the front runner, grows in depth, velocity, celerity, and wavelength with distance from the localized disturbance. The front-runner wave amplitude depends on the distance from the localized disturbance, the power law index, the plug-layer thickness, and the Froude number. We calculated the front-runner's wave amplitude due to a line source of disturbance in a 1D unidirectional development and the roll waves' 2D development due to a point source. The initial nonlinear growth in the 2D front runner is a fraction of the 1D waves, but the increase in the wave amplitude with distance follows the same trend. We have also conducted a mesh refinement study to determine the convergence and accuracy. The present simulations using 64 layers have attained an accuracy within a 2% error. [ABSTRACT FROM AUTHOR]

An adaptive differential-phase-shifting (DPS) quantum key distribution (QKD) protocol improved by encoding asynchronous-bit-rate with harmonic clock tunability, decoded by shortened delay-line interferometer (DLI) with enhancing stability, and received by single-photon detection with long hold-off is demonstrated to realize low-erroneous transmission. To achieve long-term stabilized visibility with a maintained quantum bit-error-ratio (QBER) and secure key rate, the shortened and polarized DLI enlarges its free-spectral range (FSR) and reduces its power-to-wavelength slope (δP/δλ) to suppress its sensitivity to thermal gradient, channel leakage, and wavelength disturbance. Extremely low power and wavelength drifts of ΔP/P < ±0.02% and Δλ/λ = ±6.45 × 10−8 can be achieved, even when using a single-mode QKD carrier with a relatively broadened 300-kHz linewidth. Flexibly expanding the 1-bit-delay FSR of the polarized DLI from 0.04 to 1.00 GHz improves its immunity to environmental disturbances, enabling the DPS-QKD decoding with 210–213 patterns, 3.2% QBER, and 17.46-kbit/s under 0.22 photon/pulse in average. The asynchronous-bit-rate DPS-QKD protocol enables harmonic expansion of DLI's FSR at limited single-photon avalanche detector's bit rate, which lengthens the duration of stable visibility to support long-pattern DPS-QKD. [ABSTRACT FROM AUTHOR]

Photonic integrated circuits based erbium doped amplifiers have attracted great interest due to their compact footprint, high gain in the telecom C-band, and high scalability for functional integration. In this work, a wavelength division multiplexer integrated erbium doped waveguide amplifier fabricated on the thin film lithium niobate on insulator platform is demonstrated. An on-chip saturated power of 10 dBm with the net gain around 10 dB is achieved from the monolithically integrated amplifier chip with the footprint of only 3 × 5 mm2. In particular, the suppression of parasitic lasing in the waveguide amplifier is realized thanks to the spectral response of the integrated wavelength division multiplexer. Theoretical analysis of parasitic lasing on amplifier performance is also conducted. The demonstrated integrated erbium doped waveguide amplifier will find great use in various applications based on the thin film lithium niobate on an insulator platform. [ABSTRACT FROM AUTHOR]

Mid-infrared (MIR) silicon photonics have attracted great interest for potential applications in on-chip spectroscopy, free-space communication, and remote imaging. Currently, the high-performance and fabrication-friendly fiber-to-chip grating couplers operating at 3–4 μm wavelength band are still desired urgently. Here, we propose an efficient method for designing a 2D subwavelength grating coupler. The few analytical fitting parameters defining the subwavelength grating periods and fill factors in two dimensions enable a high design degree of freedom and a low search space dimension, resulting in high figure-of-merit and fast convergence simultaneously. The developed 3.7 μm grating coupler showcases record-high coupling efficiency both theoretically (−2.2 dB) and experimentally (−4.4 dB) among the 3–4 μm MIR counterparts. This study provides an effective method for designing fiber-to-chip grating couplers, by which the MIR grating couplers with high performance and fabrication ease are developed, thus paving the way for developing high-performance silicon photonic integrated circuits operating in the MIR wavelength band. [ABSTRACT FROM AUTHOR]

Seismic attributes have been widely utilized for fault detection; however, accurately characterizing mesoscale fractures (1/10 to 1/4 wavelength) using these attributes remains challenging, particularly in complex geological setting. To explicitly reveal the effectiveness of seismic attributes in fracture characterization, we constructed a realistic physical model based on the stratigraphic structure of a real shale-gas play. This model incorporates several faults and six fracture zones containing vertically aligned mesoscale fractures of varying fracture densities, embedded in a target layer of 40 m equivalent thickness. Through a comprehensive evaluation of various seismic attributes, we demonstrate that, while these attributes effectively map faults or macroscale fractures, they are less reliable for characterizing mesoscale fractures. Although mesoscale fractures induce anomalies in seismic amplitude and attributes, the magnitude of these anomalies does not correlate with the fracture density. To address this limitation, we introduce the amplitude at the dominant frequency (ADF) attribute, designed to characterize fracture density in thin beds with mesoscale fractures. A strong relationship is observed between fracture density and the ADF attribute, with a correlation coefficient of 0.8067. Thus, the ADF attribute serves as a valuable tool for interpreting seismic data in the context of mesoscale fracture density. [ABSTRACT FROM AUTHOR]

A small-sized, circular-shaped Multiple Input Multiple Output (MIMO) antenna is investigated in this study. This antenna is suitable for wireless applications at 2.4 GHz and 5 GHz. The MIMO antenna comprises two identical, back-to-back slotted circular patch antennas with a common ground plane. The radiation direction of each antenna is oriented at 180° relative to its counterpart, providing good isolation between them. The novelty of this two-port MIMO antenna lies in its compact size of only 0.001λ ³ (where λ corresponds to the free space wavelength at 2.4 GHz) along with its dual-band 0 0 operating capability. Important parameter values of this MIMO antenna are analyzed using electromagnetic analysis software. Directivity values of 5.5 dBi (at 2.4 GHz) and 6.7 dBi (at 5 GHz), as well as reasonable bandwidths of 50 MHz (at 2.4 GHz) and 160 MHz (at 5 GHz), are obtained for this antenna. Envelope Correlation Coefficients (ECC) of 0.01 at 2.4 GHz and 0.003 at 5 GHz, along with a nearly 10 dB Diversity Gain (DG), are achieved at both frequencies for this compact antenna system. The ratio of Mean Effective Gain (MEG) between the two antennas is found to be 0.02 dB at 2.4 GHz and 0.05 dB at 5 GHz. Channel Capacity Loss (CCL) values of 0.16 bits/s/Hz and 0.089 bits/s/Hz are obtained at 2.4 GHz and 5 GHz, respectively. The characteristic parameters of this two-port circular patch antenna system are compared with those of similar antennas reported in recent literature. [ABSTRACT FROM AUTHOR]