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Efficient and anisotropic strain engineering in few-layer 3R-MoS2 via polymer encapsulation
Efficient strain transfer to few-layer two-dimensional materials remains challenging due to weak interfacial coupling. Here, we apply uniaxial tensile strain up to 4.3% to few-layer 3R-MoS2 using a polymer encapsulation approach on a flexible polyethylene terephthalate substrate. The in-plane lattice vibrations and exciton emissions exhibit pronounced anisotropic modulation efficiency. The response is strongest along the zigzag direction, yielding a maximum phonon mode splitting of 10.81 cm−1 and a bandgap modulation of 175.8 meV, values that surpass those reported for most monolayer and few-layer 2H-MoS2. This work offers a general and effective strain-engineering approach for exploring strain modulation in other few-layer two-dimensional materials.
GaN-based blue micro-laser diodes for visible light communication
Visible light communication (VLC) is attracting growing interest for energy-efficient, high-bandwidth links for next-generation data centers. GaN-based blue edge-emitting micro-laser diodes (micro-LDs) with cavity lengths down to 40 μm are demonstrated based on optical resonance between a cleaved facet and an etched facet with laterally deposited distributed Bragg reflector. The threshold current as low as 9.6 mA and slope efficiency of 0.32 W/A are achieved for an 80 μm-cavity-length device. The VLC characteristics of 140 μm micro-LD show a broader −3 dB modulation bandwidth of 429 MHz and a higher data rate of 5.3 Gbps, compared with those of standard 500 μm LD. These results demonstrate the potential application of GaN-based blue edge-emitting micro-LDs as a compact and low-power laser platform for augmented/virtual reality displays and short-distance optical communication for inter-chip optical interconnections.
Full-color imaging diffractive lenses fabricated by two-photon lithography
Diffractive lenses allow bulky refractive optical elements to be replaced by compact solutions, making them essential for miniaturized optical systems. However, diffractive lenses suffer from strong chromatic aberrations, which severely limit their applicability in imaging systems operating over a finite spectral bandwidth, such as the visible spectrum. We employed two-photon lithography to achieve full-color imaging in diffractive lenses with an engineered phase profile incorporating a third-order nonlinear term.
Deep-ultraviolet AlGaN laser diodes employing a low-resistivity n-type contact layer
We demonstrate deep-ultraviolet (UV) AlGaN laser diodes (LDs) employing a Si-doped compositionally graded AlGaN n-type contact layer. The introduction of this contact layer significantly improved the Ohmic contact properties even for high-Al-content AlGaN (Al > 80%), yielding a low specific contact resistivity of 8.1 × 10−5 Ω cm2, thereby reducing the operating voltage and enhancing electron injection in the LDs. As a result, the LDs exhibit lasing at 284.1 nm with a threshold current density of ∼13.5 kA/cm2, lower than that of reference LDs without the contact layer. In addition, the electroluminescence intensity is approximately five times higher than that of LDs without the contact layer at 500 mA. These results indicate that the n-type contact layer plays a key role in enhancing electron injection in deep-UV AlGaN LDs.
Unveiling asymmetric carrier dynamics and space-charge compensation in InGaN/GaN multiple quantum wells via capacitance transient spectroscopy
Carrier dynamics, particularly the transition between localized and delocalized states within quantum wells (QWs), are fundamental to the performance of InGaN/GaN optoelectronic devices. In this work, an anomalous capacitance transient phenomenon was observed using a custom-designed photoelectric synergetic transient spectroscopy system. We demonstrate that the thermal activation process of multiple QWs is fundamentally distinct from classical point-defect signatures. Due to polarization-induced asymmetric potential barriers, thermally emitted carriers from 2D ground states to 3D continuum states are not fully released as free charges but remain localized near the space-charge region. These localized carriers act as dynamic compensation centers, triggering a macroscopic redistribution of the space charge to re-establish electrostatic equilibrium. By varying bias conditions, we distinguish the non-equilibrium dynamics of depletion region expansion and contraction. This study provides a new framework for characterizing carrier transport and spatial charge redistribution, offering a definitive clarification of the non-equilibrium physics in nitride-based quantum structures.
Tailoring imprint in ferroelectric thin films through substrate work function
The imprint effect, one of the most critical parameters in ferroelectrics, manifests as an asymmetry in polarization reversal. The precise control of imprint is essential for reliable implementations of ferroelectric materials in many applications. In this study, we demonstrate that imprint can be tuned in Bi2FeCrO6 (BFCO) thin films by changing the nature of the underlying layer. Specifically, BFCO(111) films deposited on Nb-doped SrTiO3 (Nb:STO) and SrRuO3 (SRO) exhibit distinct imprint characteristics. Piezoresponse force microscopy reveals a consistent imprint difference of about 1 V between BFCO/Nb:STO and BFCO/SRO, which correlates with the work function difference between the two substrates. These findings underscore a generalizable mechanism for imprint control in ferroelectric heterostructures and hold particular relevance for applications demanding fine polarization management.
On-chip THz photonic receivers with built-in frequency selectivity
Miniaturized terahertz (THz) photonic receivers with built-in frequency selectivity are crucial for integrated THz sensing and communication systems. Silicon photonic crystal waveguides (PCWs) provide a dispersion-engineered platform for THz guiding, yet realizing compact, highly sensitive, and well-isolated multi-channel receivers on a single chip remains challenging. Here, we demonstrate an integrated three-channel THz photonic crystal detector based on an isosceles-triangle-lattice PCW side-coupled to multiple point-defect cavities, each hosting a monolithically integrated Nb5N6 microbolometer. Three spatially separated cavities define distinct narrowband channels around 0.43 THz for on-chip frequency-division-multiplexed detection. By converting a single silicon PCW into a scalable, frequency-division-multiplexed detector array, this work offers a practical route toward integrated THz spectrometers and multi-band front ends for on-chip THz microsystems.
Pulse-interval-dependent cavitation bubble expansion for high-speed particle manipulation by femtosecond laser irradiation
Focused irradiation of femtosecond laser pulses into an aqueous solution induces cavitation bubbles (CBs) through explosive water vaporization, generating impulsive forces that can be harnessed for particle manipulation. For applications such as high-speed cell sorting, achieving controllable and sufficiently large forces is essential. Multiple-pulse irradiation provides an effective and feasible approach, as each CB undergoes microsecond-scale expansion and contraction, producing alternating push–pull forces. In this study, we investigated the effect of pulse-to-pulse intervals (up to 12 μs) on particle displacement, enabling selective enhancement of the net force under the double pulse irradiation case. Optimized intervals of 10 μs for beads and cells were identified. The results demonstrate that dual CBs via double-pulse irradiation allow rapid and controllable manipulation of microparticles, offering a powerful strategy for high-speed, flexible cell handling in microfluidic devices, including separation and sorting.
Measurement of the laser pulse phase velocity in plasma channel for DLA optimization
We demonstrate a novel, direct method for measuring the phase velocity vϕ of an intense laser pulse within a plasma channel—the crucial parameter that controls the resonance condition in direct laser acceleration (DLA). The technique exploits the second harmonic (SH) radiation generated at the channel sheath—a phenomenon previously observed in laser-wakefield acceleration experiments. The SH emission angle is governed by a phase-matching condition that directly depends on vϕ. Experimental measurements performed using a 1 TW, 10 Hz Ti:Sa laser system yield phase velocities in the range vϕ=(1.010−1.030)c for plasma electron densities in the range ne=(0.01−0.06)ncr. The diagnostic is validated through quasi-3D particle-in-cell simulations that reproduce the experimental conditions. This work provides a way to optimize DLA schemes by enabling in situ measurement of the laser pulse phase velocity in plasma channels.
Laser lift-off process for blue GaN micro-LED automotive digital headlights
Laser lift-off (LLO) is a critical bottleneck in the fabrication of micro-light-emitting diode (micro-LED)-based automotive digital headlights. In this work, a patterned sapphire substrate was successfully removed from a 0.61-in. monochromatic GaN-based blue micro-LED array using a laser lift-off process. The micro-LED chip has a pixel size of 32 × 32 μm2 and a resolution of 370 × 110. LLO was performed on the bonded micro-LED chip using a 248 nm KrF excimer laser. Optical microscopy and scanning electron microscopy observations reveal that the GaN layer in the light-emitting regions remains intact after the LLO process. A comprehensive analysis of the optoelectronic properties of the micro-LED before and after LLO was performed. The current–voltage (I–V) characteristics indicate that the turn-on voltage remains essentially unchanged after the LLO/HCI process. In addition, electroluminescence spectra measured at different injection currents reveal a slight blueshift of the peak wavelength after lift-off. The luminance and external quantum efficiency are enhanced by 33% and 22.7%, respectively. These results demonstrate the effectiveness of LLO in optimizing micro-LED performance and highlight its potential for advanced display applications, providing a scalable solution for subsequent LLO and laser-based mass transfer processes.
Spin–orbit interaction mediated by a nonseparable twist phase of light
Spin–orbit interaction (SOI) of light provides a fundamental mechanism for controlling optical angular momentum, with applications ranging from light manipulation to quantum information processing. Conventionally, SOI is regarded as an intrinsic property of vector vortex beams arising from the coupling between vortex phase and polarization but is generally weakened in low-coherence optical fields. Here, we demonstrate a distinct form of SOI in tightly focused partially coherent vortex beams, mediated by an intrinsic nonseparable twist phase. We reveal that twist and vortex phases represent two independent mechanisms for orbital angular momentum (OAM) generation, whose interplay fundamentally reshapes angular momentum conversion processes. In orbital-to-spin conversion, the chirality of twist phase determines the sign of the longitudinal spin angular momentum (SAM) density, while the spatial coherence width governs the effectiveness of the conversion, enabling on-demand generation of localized SAM. In spin-to-orbital conversion, OAM induced by the twist and vortex phases undergoes constructive or destructive coupling, yielding tunable longitudinal spectral density distributions ranging from Gaussian-like to doughnut-like profiles. These results establish partial coherence engineering as a versatile platform for tailoring SOI of light, opening avenues for advanced structured light generation and nanoscale optical manipulation.
Highly sensitive multi-frequency acoustic sensor based on a high-Q graded hollow-core optical microcavity
A highly sensitive multi-frequency acoustic sensor based on a high-quality-factor (Q-factor) graded hollow-core optical microcavity (GHCOM) is proposed and experimentally demonstrated. The GHCOM, fabricated by a pressure-controlled fusion-tapering method, exhibits an ultrahigh Q-factor exceeding 107. The graded geometry, with a high aspect ratio of >21, significantly enhances pressure sensitivity. Theoretical analysis reveals that reduced wall thickness of the GHCOM results in increased vibration amplitude and the eigenfrequency under identical acoustic excitation. Through optimized design, a GHCOM with an outer diameter of 138 μm and a wall thickness of 2 μm is fabricated. The measured frequency response spans from 0.2 to 19 kHz, covering nearly the entire audible frequency range. A signal-to-noise ratio (SNR) of 50 dB is achieved at 1 kHz, corresponding to a minimum detectable pressure of approximately 14.7 μPa/Hz1/2. Moreover, the sensor exhibits excellent multi-frequency detection capability, with SNRs of 51 and 55 dB for dual-frequency signals at 6 and 7 kHz, respectively, and 49, 50, and 46 dB for triple-frequency signals at 7, 8, and 9 kHz, respectively. Directional response measurements indicate SNRs exceeding 24 dB for acoustic signals incident from all angles, demonstrating the sensor's robust and comprehensive acoustic sensing performance.
Improved ferroelectric properties in lanthanide-doped HfO2 thin films epitaxially grown on yttria-stabilized zirconia substrates
Hafnium oxides are important ferroelectric materials that can be compatible with current silicon-based technology. However, the polar orthorhombic (o) phase is a metastable state, which is hard to control and results in low effective polarizations. In this work, we report improved ferroelectric properties in lanthanide-doped HfO2 thin films with controllable epitaxial growth on (001)-orientated yttria-stabilized zirconia substrates. Ce, Nd, and Eu elements are selected as the doping cations and the ferroelectric o phase is found to be stabilized in the (100)o family of crystal planes in Nd- and Eu-doped HfO2 thin films. In addition, at the Eu concentration of 7.5 at. %, a (001)o-orientated texture—the polar axis direction of o phase—is achieved in the HfO2-based heterostructure, yielding well-saturated ferroelectric hysteresis loops and improved remanent polarizations (Pr) of ∼37 μC/cm2. The optimized Eu-doped HfO2 also exhibits good reproducibility, long-term retention with the bistable polarizations up to 10 years, and strong fatigue resistance with a large readout margin (2Pr) of ∼60 μC/cm2 observed above 1.0 × 108 fatigue-free cycles. Even after 1.0 × 1010 cycles, the Pr is decreased by only 25%. These performances are outstanding in ferroelectric HfO2-based films and shed light on the material designs of high-performance nonvolatile memories.
Evaluating machine learning algorithms at predicting developmental trajectories using sequential dataset truncation of voluntary alcohol consumption in adolescent mice
Background Adolescent alcohol consumption is a known risk factor for developing alcohol use disorder (AUD) in adulthood, but individual susceptibility varies widely, contributed to by differences in factors that are not well-understood. Identifying patterns of developmental trajectories in voluntary alcohol consumption behavior during adolescence could provide insight into biological underpinnings of AUD risk. Machine learning (ML) offers powerful pattern recognition capabilities that may help forecast future behavioral trajectories based on early-stage data. Objective This study aimed to evaluate the performance of twelve supervised ML algorithms in predicting developmental trajectories of voluntary alcohol consumption behavior in adolescent mice using sequentially truncated datasets. Methods Simulated balanced datasets of alcohol consumption in adolescent mice were generated based on previously published biological data. We applied a sequential dataset truncation strategy to train and evaluate ML models on progressively longer spans of behavioral data. Prediction accuracy for trajectory pattern classification was assessed for each truncation point, and goodness-of-fit was modeled using four curve-fitting equations, including locally estimated scatterplot smoothing (LOESS), which provided best fit and was selected for downstream comparative analysis. Results LOESS-fitted accuracy progression curves enabled quantitative comparison across models. Six ML algorithms—Random Forest, Logistic Regression, Multilayer Perceptron, Linear Discriminant Analysis, K-Nearest Neighbors, and Support Vector Machine—achieved outstanding results, with 98% or better prediction accuracy by experiment end and 90% or better accuracy at midpoint. Four additional algorithms—Stochastic Gradient Descent, Decision Tree, Gradient Boosting Classifier, and Multinomial Naive Bayes—achieved acceptable accuracy values (77–95% at midpoint, and 91–96% at experiment end). In contrast, two models (Quadratic Discriminant Analysis and Gaussian Process Classifier) performed poorly and displayed declining accuracy trends with more data. Conclusions This study demonstrates that certain supervised ML algorithms can accurately predict behavioral outcomes from early-stage data. This approach holds promise for guiding molecular and cellular analyses at time points prior to behavioral phenotype’s fully manifesting, making it possible to identify potential biological drivers that initiate the onset of harmful behavior of alcohol consumption during adolescence development.
High-frequency AC line filtering with silicon carbide-based flexible supercapacitors
Filtering supercapacitors (SCs) are emerging as a potential alternative to bulky aluminum electrolytic capacitors (AECs) for compact power filter electronics, thanks to their high capacitance and fast charge/discharge performance. However, achieving high-frequency responsiveness and effective ripple suppression remains a significant challenge. Although silicon carbide (SiC) has demonstrated great potential as a supercapacitor electrode material, its capabilities for high-frequency applications have not been fully realized due to limitations in current fabrication methods. Therefore, ultra-ultrafast flexible symmetric supercapacitors (FSSCs) using SiC thin films with finely tailored porous nanostructures are fabricated using a binder-free magnetron sputtering method for stable filtering over a wide frequency range. The optimized FSSCs deliver an impressive high-frequency response (f0) of 3.2 kHz, a high volumetric capacitance of 0.67 F cm−3 at 120 Hz, and an outstanding cycling stability of 84.39% after 25 000 cycles. This superior performance is attributed to the synergistic effect of the nanocauliflower morphology and the ultrathin electrode design, which facilitates surface-dominated charge storage and shortens ion transport pathways for efficient alternating current (AC) line filtering. Furthermore, the FSSC smooths the AC signal (2.65 V; 50 Hz) into a direct current (DC) output, exhibiting an 80 mV fluctuation, 4.5 times smaller than that from the AEC (360 mV). The FSSCs successfully filter AC waveforms at a high frequency of 2 kHz into stable DC signals with minimal ripple, underscoring their potential for next-generation electronics.
An umbrella review navigating the nationwide burden of hepatitis B virus infection in Ethiopia: A call for action on vaccination, safe blood, and infection prevention
Background The Hepatitis B virus (HBV) is one of the major causes of viral hepatitis that may persist and lead to complications, including cirrhosis, hepatic decompensation, and liver cancer. Numerous systematic reviews and meta-analysis have been conducted on HBV infection among people in Ethiopia, showing inconsistent findings. This umbrella review aimed to assess the pooled prevalence of HBV infection and its associated factors among people in Ethiopia. Methods All published and unpublished systematic review and meta-analysis studies were searched on databases such as PubMed, Scopus, HINARI and Google Scholar. A measurement tool to assess systematic reviews was used for critical appraisal of the included studies. STATA software version 17 was used to conduct the analysis. I 2 test were used to determine heterogeneity, whereas funnel plots and Egger’s regression tests were used to assess publication bias. To pool the prevalence of HBV infection, a random-effects model was used and presented using a forest plot. Results Twelve systematic reviews and meta-analysis with 997,264 participants were included in this umbrella review. The pooled prevalence of the HBV infection among people in Ethiopia was 5.78% (95% CI: 5.33, 6.23). Being male, having multiple sexual partners, having a history of abortion, having body tattoos, having a history of tooth extraction, sharing sharp material, and linked to health system such as having a history of hospital admission, and blood transfusion were significant risk factors associated with HBV infection among people in Ethiopia. Conclusion This study highlights that the prevalence of HBV infection among people in Ethiopia was relatively moderate endemicity as per WHO classification. By synthesizing evidence of prior review, this study provides specific up-to-date information for clinicians and policymakers to design evidence-based public health strategies and guide future research that enable the prevention, control, and eliminate infection of HBV. PROSPERO Registration : CRD420251160887
Ultraviolet attenuation–absorption microscopy with an opto-acoustic confocal dual-sensitive sensor and its application in pathological diagnosis
Pathological analysis is essential for cancer diagnosis and treatment. However, the current gold standard based on hematoxylin and eosin (H&E) staining is time-consuming and requires exogenous labels. This study presents an ultraviolet attenuation–absorption dual-mode photoacoustic microscopy system for label-free imaging of histological sections. Enabled by the carbon nanotubes-polydimethylsiloxane film, the opto-acoustic dual-sensitive sensor simultaneously detects optical and acoustic signals, and its opto-acoustic confocal design improves the peak amplitude by 24 dB compared to the planar structure. Between the two imaging modes, the UV absorption image reveals cell nuclei, providing virtual hematoxylin staining contrast, whereas the UV attenuation image highlights tissue structures, achieving virtual eosin staining contrast. In the imaging of pathological sections of human oral cancer tissue, the hybrid images reveal critical pathological features, such as nuclear size and the tumor invasive front, similar to those observed in H&E-stained sections, supporting the proof-of-concept validation of this technique for rapid intraoperative pathological analysis.
Trends and determinants of acute tocolysis implementation in Japan, 2012–2023: An 11-year nationwide retrospective cohort study
Background International guidelines, such as those from the WHO, recommend limiting the duration of tocolysis to up to 48 hours in order to provide a window for antenatal corticosteroid administration and maternal transfer. However, reports from multiple countries indicate that tocolysis is being performed for 48 hours or longer in actual clinical settings. This study used nationwide data in Japan over an 11-year period to investigate changes in tocolytic protocol and identify factors associated with tocolysis within 48 hours. Methods Using the Diagnosis Procedure Combination database, we analyzed data from 156,356 pregnant women who received ritodrine infusion for preterm labor between April 2012 and March 2023. To accommodate day-based administrative data, we defined acute tocolysis (AT) as ≤2 and maintenance tocolysis (MT) as ≥4 days of treatment. Annual trends in AT utilization rates were examined, and logistic regression analysis was performed to identify factors associated with AT, including institutional characteristics, regional differences, and obstetric complications. Results The rate of AT utilization increased from 15.73% to 23.74% over the study period, as did variation among hospitals. University hospitals (adjusted odds ratio [aOR] = 1.16), perinatal centers (aOR = 1.12), preterm premature rupture of membranes (aOR = 3.18), and pregnancy-induced hypertension (aOR = 1.52) were associated with AT, while concomitant use of magnesium sulfate hydrate (aOR = 0.91), multiple fetuses (aOR = 0.64), and placenta previa (aOR = 0.67) were negatively associated with AT utilization. Conclusions While AT utilization has increased over time, significant disparities between facilities remain. These findings suggest that the choice of tocolytic protocol is not determined by evidence alone, but is complexly influenced by institutional roles, regional healthcare systems, and specific maternal complications. This study highlights the importance of understanding these multifaceted factors to optimize treatment strategies that balance international standards with the practicalities of individualized patient care.
Self-rectifying organic memristor based on PAA/PEDOT:PSS heterojunction for neuromorphic computing
Neuromorphic computing has emerged as a promising strategy to overcome the intrinsic limitations of the von Neumann architecture, where memristive devices that emulate biological synapses are of particular interest. Among them, organic memristors offer unique advantages in mechanical flexibility, biocompatibility, and solution processability. Here, we report a flexible, self-rectifying organic memristor fabricated on an ITO/PAA(Ca2+)/PEDOT:PSS/ITO architecture. The device operates through directional Ca2+ migration within the poly(acrylic acid) (PAA) electrolyte layer, enabling stable resistive switching. Importantly, the integration of PEDOT:PSS with ITO forms an intrinsic p–n junction, imparting pronounced self-rectifying behavior with a rectification ratio of approximately 103, effectively suppressing sneak-path currents in crossbar arrays. The device is able to simultaneously maintain stable resistive switching and robust rectification, avoiding the mutual interference commonly observed in conventional designs. The memristor reliably reproduces key synaptic functions, including transitions from short-term to long-term potentiation and depression, as well as spike-timing-dependent plasticity. Artificial neural networks constructed using experimentally extracted device characteristics achieve image and digit recognition accuracies exceeding 90%. This work demonstrates that flexible organic memristors with built-in p–n junction rectification can simultaneously address mechanical compliance, energy efficiency, and integration density, thereby establishing a viable materials and device platform for biocompatible neuromorphic hardware and scalable pattern-recognition systems.
Cold stress during winter over North India: Patterns, trends, and mortality risks
The cold temperatures during winter contribute to significant discomfort, causing cold stress to the lives of people. In this study, we investigate the cold stress conditions and their trends over north India during November – February for the period 1982−2020, using Universal Thermal Climate Index (UTCI), a widely recognized biometeorological variable. The onset of cold stress typically initiates in the late evening (18 IST) and gradually spreads across the north India. It then intensifies over night into moderate cold stress, persisting from 20 IST until the early morning hours (7 IST). Cold stress is found to be most intense in January, with UTCI values ranging between 0 °C to −13 °C among winter months. During cold wave events, cold stress reaches its maximum spatial extent and intensity throughout the study region, with the most intense conditions observed in Jammu & Kashmir and Ladakh. Results show a significant increase in slight cold stress hours during the winter season over the period 1982−2020 in north India. This increase reflects a transition from stronger cold stress categories to the slight cold stress category. Such a shift indicates a reduction in the severity of cold stress rather than an intensification of cold conditions. Slight cold stress occurs when UTCI values range between 0 °C and −9 °C and the duration of such conditions has increased at a rate of 33.64 hours per decade. This increase is most prominent in the high-altitude regions of Jammu & Kashmir, Ladakh and Himachal Pradesh. In contrast, moderate cold stress which occurs when the UTCI values are in the range −9 °C to −13 °C shows a significant decreasing trend, particularly in Rajasthan, Punjab, Haryana and Uttar Pradesh. Despite this, cold stress remains a major contributor to cold wave-related mortality in north India. Uttar Pradesh recorded the highest number of deaths of 4449, followed by Punjab (2606) and Bihar (2479). Although these states generally experience only slight cold stress with UTCI values in the range of 0 °C to 9 °C, the impact is amplified by wind chill with a category of ‘Tonic- very cold sub comfort’ caused by cold, dry northwesterly winds blowing directly into the region. This compound effect of cold stress and wind chill considerably enhances the mortality risk during cold wave events across north India.