Search Results (1,925)

To investigate the polarization characteristics of AlO molecular emission in femtosecond laser-induced aluminum plasma, AlO molecular spectra were generated by irradiating an aluminum target with a femtosecond laser. The experimental results revealed a pronounced polarization response in the AlO emission. After a polarizer was introduced into the collection path, the signal-to-background ratio (SBR) increased from 8.30 to 10.80, while the relative standard deviation (RSD) decreased from 0.043 to 0.036, indicating improved spectral quality and stability. By modulating the laser polarization state using a half-wave plate and a quarter-wave plate, the AlO spectral intensity increased by a factor of 1.26 when the laser polarization was changed from horizontal to vertical, and by a factor of 1.75 when it was changed from linear to circular. Under circular, horizontal, and vertical polarization conditions, the SBR values obtained with a polarizer were consistently higher than those obtained without a polarizer, with the maximum value of 12.46 achieved under vertical polarization. These results demonstrate that both plasma polarization detection and laser polarization modulation can effectively achieve better-quality AlO molecular spectra. This work provides a useful reference for improving molecular spectral quality in femtosecond laser-induced spectroscopy. Full article

To meet the demand for high-capacity indoor wireless access in future 6G systems, we propose and experimentally demonstrate a photonics-aided D-band wireless transmission scheme operating at 138 GHz. At the transmitter, two external-cavity lasers together with an I/Q modulator are used to generate a modulated D-band carrier. At the receiver, homodyne down-conversion is employed to directly recover the received signal to baseband, thereby relaxing the requirements on ultra-wideband analog components and high-speed sampling hardware. A 20 m indoor line-of-sight wireless link is established to transmit a 56-Gbaud-rate OFDM-QPSK signal. The transmitted and received spectra, received constellations and bit-error-rate (BER) performance are functions of optical power at different symbol rates, and the channel amplitude and phase responses are systematically analyzed. The results show that broadband D-band signal generation, transmission, and recovery can be stably achieved in the proposed system. After receiver-side digital signal processing (DSP), clear QPSK constellations are obtained. BER measurements reveal an optimal optical-power operating range, and the 32-GBaud OFDM signal outperforms the 56-Gbaud-rate signal because its narrower occupied bandwidth makes it less sensitive to frequency-selective distortion. For 56-Gbaud-rate OFDM transmission, the BER approaches the 20% low-density parity-check forward-error-correction threshold at an optical power of approximately −1 dBm. Further analysis indicates that the current link performance is mainly limited by frequency-selective amplitude and phase distortions under bandwidth-constrained conditions, together with slight nonlinear effects at high power. These results verify the feasibility of a photonics-aided D-band wireless architecture with homodyne reception for medium-range, high-symbol-rate indoor transmission and provide an experimental basis for future 6G sub-THz wireless links. Full article

To improve the visible-light response and antibacterial performance of titanium dioxide, a TiO₂/GO/CdS mesoporous nanocomposite was prepared via an ultrasound-assisted sol–gel method in this study. Systematic characterizations including XRD, XPS, SEM, TEM, BET, UV-Vis DRS and FTIR were carried out to analyze the structure, morphology and optical properties of the material. The results show that the composite exhibits a typical mesoporous structure with a specific surface area of 197.0962 m²/g and a pore size distribution of 2–14 nm. CdS is successfully doped into the TiO₂ matrix and forms a heterostructure with GO. UV-Vis diffuse reflectance spectra indicate that the synergistic effect of CdS and GO significantly broadens the visible-light absorption range of TiO₂ and suppresses the recombination of photogenerated carriers. Antibacterial tests using Escherichia coli as the target strain demonstrate that the TiO₂/GO/CdS composite exhibits remarkably better visible-light photocatalytic bactericidal activity than pure TiO₂ and the TiO₂/GO composite. This work provides a new strategy for the modification of TiO₂-based photocatalytic antibacterial materials, and the as-prepared composite shows promising application prospects in the antibacterial field. Full article

In this study, density functional theory (DFT)-based investigations are carried out using the CASTEP code. The plane-wave pseudopotential method is used to explore the multifunctional properties, including the structural, electronic spectra, thermo-mechanical and hydrogen storage properties, of hydrogen-rich mixed-anionic (Li₃H₄N₂X, where X = F, Cl, Br, and I) halides. The exchange–correlation interactions are treated within the generalized gradient approximation (GGA) using the Perdew–Burke–Ernzerhof (PBE) functional, while the hybrid HSE06 function is used for accurate band gap predictions. Moreover, the optical properties of the halides are analyzed under the influence of UV–Vis radiation instances. The band gap values of these orthorhombic-structured halides lie in the visible-to-UV regions of radiation, with values of 2.97 eV, 3.12 eV, 3.06 eV and 3.28 eV, respectively. Such band gap values allow these materials to absorb nearly 75% to 90% of incoming radiation, with absorption values around (10⁵ cm⁻¹). These favorable opto-electronic responses make these halides suitable for solar radiation energy conversion applications. Stable thermodynamic responses and the mechanical nature of the mixes (brittle for Li₃H₄N₂Br and ductile for the rest) reveal their practical applicability for flexible photonics. Moreover, due to the presence of rich hydrogen atoms, the Li₃H₄N₂F halide exhibits a gravimetric ratio of around 6.0 wt%, which is higher than the standard (5.5 wt%) value defined by the US DOE. Similarly, GHSC values of 2.5 wt% for Li₃H₄N₂I, 3.5 wt% for Li₃H₄N₂Br, and 5.0 wt% for Li₃H₄N₂Cl are reported; these values indicate that these compounds possess strong potential for use in the hydrogen fuel cells required in light-duty vehicles. Full article

The increasing adoption of alternative fuels such as hydrogen and ammonia in energy systems has created a growing need for advanced diagnostic techniques capable of monitoring combustion products with high specificity and flexibility. In this context, Raman spectroscopy represents a promising optical approach for gas analysis, as it enables the simultaneous detection of multiple species without requiring sample preparation. In this work, the performance of a cost-effective Raman-based system on quantitative detection of nitrogen oxides (NO and NO₂) and nitrous oxide (N₂O) is presented. The experimental setup is based on a multi-pass optical configuration designed to enhance the Raman signal and employs off-the-shelf components, including an uncooled CMOS detector. Calibration measurements were carried out using gas mixtures at known partial pressures, and gas concentrations were retrieved through a nonlinear least-squares fitting procedure applied to the measured spectra. The results show that the system provides linear and repeatable responses for NO and N₂O over the investigated pressure ranges, with low mean errors and limited data dispersion, while NO₂ performance could not be fully quantified in a comparable manner due to the high reactivity of the species under the tested conditions. Overall, the proposed system represents a viable and cost-effective solution for multi-species gas analysis in emerging combustion applications. This work aims to extend the industrial applicability of Raman spectroscopy to NO_x and NO₂ diagnostics. Full article

Extending the fruiting season of Annona squamosa L. requires overcoming autumn and winter flowering declines. This study investigates the efficacy of light-quality regulation technologies and their temperature dependence for floral induction. Field surveys initially identified temperature as the primary climatic factor governing flowering. Under suboptimal autumn temperatures, red light (R-660) night-break (NB) treatments significantly enhanced shoot growth and flowering compared to other light spectra. Transcriptomic analysis revealed 2027 upregulated and 341 downregulated transcripts consistently regulated by R-660, with significant enrichment in the plant hormone signal transduction pathway. Furthermore, R-660 upregulated cold response genes (e.g., CBFs, WRKYs, ERD7), which are associated with the maintenance of vegetative vigor under suboptimal autumn temperatures. However, mid-winter R-660 NB failed to induce flowering without supplemental greenhouse heating. Ultimately, warm ambient temperature is the absolute prerequisite for A. squamosa floral induction, with R-660 serving as a highly effective seasonal supplement to extend autumn flowering. Full article

In this study, zinc sulfide (ZnS) and manganese (Mn)-doped ZnS nanopowder were successfully prepared via a simple and cost-effective chemical precipitation method with various concentrations of Mn for use in UV photodetectors. The effects of Mn doping on the structural, morphological, and optoelectronic properties of ZnS nanopowder were studied. Structural analysis showed that all samples had a cubic structure with crystallite sizes approximately in the region of 2–3 nm. The morphological analysis using scanning electron microscopy confirmed the formation of well-dispersed spherical nanoparticles. Photoluminescence spectra show that Mn doping increased the luminescence intensity and caused a red shift in the emission peaks. Electrical properties such as conductivity and dielectric constant showed marked improvement with increasing Mn content. The conductivity increased from 3.7 mΩ⁻¹·m⁻¹ for pure ZnS to 6.3 mΩ⁻¹·m⁻¹ for the 1.03 mol% Mn²⁺ sample. The performance of photodetectors was evaluated under UV light. It was revealed that the photodetector based on a sample with 1.03 mol% Mn²⁺ reached an optimum state with an EQE of 9.8%, a detectivity of 4.65 × 10⁹ Jones, and a responsivity of 3.64 × 10⁻² A/W, indicating the effectiveness of Mn doping in improving the photo-generated carrier collection. Full article

Flat bands exhibit vanishing group velocity and marked sensitivity to lattice geometry, making them a useful setting for studying localization driven by destructive interference. In this work, electrical-circuit simulations are employed to investigate flat-band systems in one, two, and three dimensions. A one-dimensional two-band circuit is first considered, and its flat-band response is characterized through node-to-ground impedance spectra and steady-state voltage distributions. The analysis is then extended to two- and three-dimensional Lieb lattice circuits characterized by sublattice imbalance. In the two-dimensional Lieb circuit, the flat band touches the dispersive bands at a Dirac point, so hybridization with dispersive modes affects the observed localization. Under periodic boundary conditions, wave vector quantization also produces responses that depend on whether the number of unit cells is even or odd. By contrast, in the three-dimensional Lieb circuit, the flat band is spectrally isolated from the dispersive bands, allowing stronger spatial confinement and clearer sublattice selectivity. The one-dimensional, two-dimensional, and three-dimensional models therefore represent three different situations: a singular flat band, a flat band that touches dispersive bands, and a spectrally isolated flat band. Comparing these cases shows how different degeneracy conditions shape impedance responses and localization patterns in electrical circuit systems. At the flat band frequency, the localized voltage response can also be used to generate spatial patterns in both two-dimensional and three-dimensional circuits, pointing to a possible route for spatial mode control of compact localized states in electrical systems. Full article

Ball resonator optical fiber sensors (OFSs) can offer multiparameter sensing capability, but their non-periodic and low-finesse reflection spectra make conventional spectral demodulation unreliable. This work proposes two sensor configurations: (i) a ball resonator and (ii) a hybrid sensor integrating a Fabry–Pérot interferometer (FPI) with a ball resonator, and compares their performance for multiparameter physiological monitoring using the Karhunen–Loève transform (KLT). The sensors were evaluated for glucose concentration (0–3 mg/mL), temperature (20–55 °C), and pH (3–9) monitoring. The ball resonator sensor, paired with KLT, achieved high linearity across all measurands (R² = 0.989, 0.919, and 0.838 in response to glucose, temperature, and pH, respectively). The hybrid sensor exhibited a higher glucose sensitivity (6.15 a.u./(mg/mL)) compared to the ball resonator (3.77 a.u./(mg/mL)), resulting in limits of detection (LODs) of 2.53 mM and 4.19 mM, respectively. In contrast, the ball resonator sensor demonstrated better sensitivity for temperature and pH sensing. Furthermore, we present a comprehensive benchmarking framework of seven spectral demodulation methods for OFSs. The results demonstrated that KLT consistently provides robust demodulation performance and highlighted the potential of KLT for multiparameter physiological sensing applications. Full article

In vertical farming systems, defining suitable lighting strategies is essential for improving crop productivity and product quality under controlled environmental conditions. This study evaluated the effects of four LED lighting configurations differing in spectral composition and lamp-to-canopy distance on the growth and selected quality traits of arugula (Eruca sativa Mill.) grown in a vertical nutrient film technique (NFT) system. Two light spectra were tested: white LED light and a red–blue LED combination, each applied at two distances from the crop canopy (20 and 40 cm). Two experiments were conducted in 2025 in a climate-controlled cultivation unit, and agronomic and quality-related variables were assessed at harvest, including fresh biomass, leaf development, total polyphenols, antioxidant capacity, chlorophyll index, and nitrate concentration. The LW20 treatment, representing a specific combination of white LED lighting, lamp-to-canopy distance, PPFD, and DLI, was associated with the highest fresh biomass, reaching 42.6 g plant⁻¹ in Experiment 1 and 70.9 g plant⁻¹ in Experiment 2, and with the highest total polyphenol content (38.4 mg GAE 100 g⁻¹ FW). In contrast, the red–blue treatments were associated with lower biomass production, while the RB20 treatment showed the lowest polyphenol concentration (26.2 mg GAE 100 g⁻¹ FW). Among the evaluated quality-related parameters, total polyphenols showed the clearest response to lighting conditions, whereas antioxidant capacity, chlorophyll index, and nitrate concentration were not significantly affected. Under the evaluated conditions, LW20 was the most favorable among the four tested lighting configurations for fresh biomass production and total polyphenol accumulation. However, this response should not be interpreted as evidence of white light superiority alone, because spectral composition, lamp-to-canopy distance, PPFD, and DLI were not independently controlled. Full article

Liquefaction-induced damages related to excess pore water pressure generation in soils and stiffness degradation significantly influence infrastructure and seismic ground response, requiring reliable experimental testing setups and validated numerical models for accurate assessment. This study investigates the free-field liquefaction behavior of saturated sands using the newly proposed ETILam (Enhanced Transparent Impermeable Laminar) soil container under 1 g shaking table conditions. Specimens composed of loose and dense saturated sands overlain by a dry sand layer were prepared and tested under two harmonic motions (0.1 g–2 Hz and 0.2 g–2 Hz), the second motion being two consecutive 6 s excitations. Dynamic response was evaluated through acceleration time histories, shear strains obtained through displacement measurements, excess pore water ratio (r_u), response spectra, transfer functions, and Fourier amplitude computations. Fully coupled effective stress analyses were performed in 2D and 3D using calibrated PM4Sand and P2PSand constitutive models. Experimental results showed limited liquefaction for the lower-amplitude motion, whereas the higher-amplitude motion triggered significant shear strains (up to 10%) and r_u values approaching 0.8, with depth-dependent dissipation patterns between sequential shakings. Numerical simulations reproduced acceleration amplitudes and general pore-pressure trends, with the 2D model providing closer agreement in both generation and dissipation behavior. The findings validate the ETILam container’s capability to simulate free-field liquefaction response and demonstrate that a well-calibrated 2D approach can reliably capture the essential features of the observed behavior. Full article

Zinc–antimony–boro–germanate glasses highly doped with Sm₂O₃ were synthesized by the conventional melt-quenching method. Their structural, optical, and luminescent properties were systematically investigated by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), diffuse reflectance UV–Vis (DR-UV–Vis), and photoluminescence (PL) spectroscopy. XRD analysis confirmed the amorphous nature of all prepared samples. XPS measurements were used to examine the surface chemical composition of the Sm₂O₃-doped glasses, with particular focus on verifying samarium incorporation and identifying its oxidation state after synthesis, since Sm ions act as the luminescent centers in these materials. For the sample containing the highest Sm₂O₃ concentration, the DR-UV–Vis spectrum exhibited ten absorption bands assigned to intra 4f electronic transitions. Based on these data, the nephelauxetic and bonding parameters were determined, indicating that increasing Sm₂O₃ content enhances the ionic character of the bonds within the glass network. PL spectra revealed three characteristic emission bands associated with Sm³⁺ luminescent centers. The emission intensity reached a maximum at 3 mol% Sm₂O₃, while further increases in samarium content led to luminescence quenching. The most intense emission band was in the yellow–orange region of the visible spectrum, highlighting the potential of these materials for yellow–orange-emitting solid-state laser applications. The excitation spectra show that the optical response is strongly dependent on concentration, with a sample doped with 3 mol% Sm₂O₃ exhibiting the highest excitation efficiency. The dominant excitation band centered near 402 nm, together with weaker bands in the blue region, indicating that these glasses are promising candidates for near-UV-pumped orange-emitting photonic devices. Full article

Metabolic heterogeneity within the cell microenvironment is a key driver of cancer progression and resistance to therapy. However, current approaches lack the spatial and temporal resolution required to capture its dynamics in living systems. While recent advances in 3D cell culture models and metabolomic profiling have improved our understanding of the tumor niche, their integration with real-time optical sensing remains underdeveloped. Here, we present an integrated platform combining a 3D-printed microreactor culture chamber with Raman spectroscopy to enable non-invasive, spatially resolved metabolic monitoring of living cell cultures. Our microreactor platform generates controlled oxygen and nutrient cues while simultaneously acquiring label-free Raman spectra, revealing extracellular metabolic fingerprints linked to cell catabolism (e.g., glucose and lactate shifts) and acidification. Analysis across four cell lines uncovered temporal evolution as the dominant source of metabolic variance, while spatial heterogeneity along oxygen gradients is a secondary factor. In particular, diffusion-limited regions exhibited localized acidification and accumulation of stress biomarkers—such as the release of nucleotides—features that cannot be detected using conventional bulk assays. By providing a versatile platform for real-time mapping, this work enables the mechanistic dissection of cell adaptation to microenvironmental stress and supports the prediction of metabolic signatures underlying drug response and treatment outcomes. Full article

In response to the increasingly severe issue of heavy metal pollution in water, this paper proposes a method for the robust quantitative analysis of copper ions in purified water and real water samples based on the feature-level fusion of ultraviolet-visible absorption (UV-Vis) spectra and fluorescence spectra, combined with the Extreme Gradient Boosting (XGBoost) algorithm. Specifically, this study introduces a feature-level fusion strategy to overcome the limitations of single-spectrum detection, while the optimized XGBoost algorithm is employed to model the complex non-linear relationships that are difficult to capture using traditional linear regression methods. An optimization algorithm is introduced to fine-tune the model’s hyperparameters, thereby enhancing its predictive performance. Using the coefficient of determination (R²) and root mean square error (RMSE) as evaluation metrics, rapid and accurate detection of copper ions in water is achieved. Experimental results show that, for standard solutions, the optimized XGBoost model achieves a coefficient of determination of 0.9915 and a root mean square error of 2.6663 mg/L; for actual water samples, the optimized XGBoost model achieved a coefficient of determination of 0.9892 and RMSE of 1.2738 mg/L. This demonstrates the model’s strong generalization ability in overcoming the physical limitations of optical probes. This method effectively identifies and quantifies copper ions in water samples, demonstrating good accuracy and stability. Full article

Artificial lighting is a central and resource-intensive component of controlled environment agriculture, directly regulating plant physiological processes while influencing energy efficiency and production outcomes. Chlorophyll fluorescence analysis, particularly pulse-amplitude-modulated fluorometry, provides a rapid and non-destructive method for assessing plants’ photosynthetic efficiency. However, the extent to which chlorophyll fluorescence reflects plant responses to different light spectra across species remains insufficiently understood. In this study, species-specific photoresponses of leafy vegetables (Amaranthus tricolor, Barbarea verna, Chrysanthemum coronarium, Perilla frutescens) to different light spectra were investigated by integrating chlorophyll fluorescence with growth, antioxidant, and pigment traits. Plants were cultivated under monochromatic red, blue, and combined red–blue light, with additional far-red supplementation. Correlation analysis was performed among growth, antioxidant parameters, pigment contents, and chlorophyll fluorescence parameters. The obtained results show that chlorophyll fluorescence parameters respond selectively, but species-specifically, to applied lighting-spectrum conditions. Relationships between fluorescence indices and physiological traits varied between species, and no single parameter consistently reflected plant performance across all crops. Therefore, to employ chlorophyll fluorescence as a useful proxy for assessing plant responses to lighting spectrum, a species-specific and context-dependent approach is required. Full article