Search Results (708)

Acaryochloris marina is a distinctive cyanobacterium that uses chlorophyll d as its primary photosynthetic pigment and possesses two major light-harvesting systems: membrane-integral chlorophyll-binding Pcb/CBP complexes and water-soluble phycobiliproteins. How these antenna systems respond at the transcriptome level to contrasting light environments remains incompletely characterized. Here, we re-analyzed a publicly available RNA-seq dataset for A. marina MBIC11017 (NCBI BioProject PRJNA1130970), comparing cells grown under low-irradiance far-red light (LL-FR; 1.5–2 µmol photons m⁻² s⁻¹, 710-nm peak) and high-irradiance white light (HL-WL; 30–35 µmol photons m⁻² s⁻¹). Because light quality and irradiance both differ in this experimental design, the two effects cannot be separated; all transcriptional changes are therefore interpreted as responses to the combined LL-FR versus HL-WL contrast rather than to far-red wavelength alone. Of 8439 expressed genes, 1810 (21.4%) were significantly differentially expressed (adjusted p < 0.05). Using GFF-verified locus tags which corrected mis-annotations propagated in earlier analyses, the PS-I core gene set showed a mean log₂ fold-change of +1.96 (3.9-fold; 11/11 loci significant), whereas the PS-II core gene set showed a mean log₂ fold-change of +1.10 (2.1-fold; 12/20 loci significant). Light-harvesting genes showed the strongest response: 17/18 phycobiliprotein-pathway genes in KEGG amr00196 were upregulated, together with multiple putative Pcb/CBP loci (mean antenna log₂FC = +3.51; 11.4-fold). Weighted gene co-expression network analysis placed the antenna-associate genes examined here within a module positively correlated with the LL-FR condition (r = 0.802, p = 0.017), and STRING analysis supported an enriched network of predicted or known protein associations (1115 nodes, 4763 edges; PPI enrichment p < 1.0 × 10⁻¹⁶). Recent matched-irradiance experiments indicate that, at equal photon flux, far-red wavelengths reduce phycobilisome content relative to white light. The transcriptional pattern reported here is therefore most parsimoniously interpreted as predominantly a low-irradiance response, with possible wavelength-associated CA5 contributions that cannot be isolated in the present design. Overall, the analysis reveals coordinated transcript-level changes across plasmid-encoded reacquired phycobiliprotein genes, chromosomal Pcb/CBP loci, chlorophyll biosynthesis genes, and photosystem core genes, consistent with coordinated regulation of light-harvesting components in A. marina. Full article

To address the challenge of accurately reconstructing multi-depth targets using single-photon Light Detection and Ranging (LiDAR) under few-frame conditions in high-precision applications such as autonomous driving perception, remote sensing, and military reconnaissance, this paper proposes a computational imaging method named the Jensen–Shannon Divergence Weighted Pixel Fusion Constant False Alarm Rate (JSWPF-CFAR) approach. First, the proposed method utilizes the Jensen–Shannon (JS) divergence to characterize the statistical similarity between adjacent pixels, thereby constructing adaptive weights to achieve the effective fusion of echo signals. The key innovation lies in the formulation of a JS divergence-based weighting factor, which fully exploits the inherent spatial correlation within 3D target structures to optimize the pixel fusion process and enhance the signal statistics of target echoes. Subsequently, a CFAR detection model tailored for Geiger-mode Avalanche Photodiode (GM-APD) multi-depth echo signals is constructed to estimate the noise photon count within a local sliding window; this estimate is then used to calculate a photon counting threshold for identifying and extracting high-confidence target intervals. Finally, a peak-picking method is employed to perform the 3D reconstruction of multi-depth targets. Compared with existing techniques such as matched filtering and Reversible Jump Markov Chain Monte Carlo (RJMCMC), the proposed method exhibits superior reconstruction quality under few-frame and low Signal-to-Background Ratio (SBR) conditions. The experimental results demonstrate that the proposed method achieves an improvement in target restoration degree (RD) of at least 21.16% and a relative variance (Var) optimization of at least 62.90% over the matched filtering and RJMCMC baselines. These results indicate that the proposed approach effectively enhances the multi-depth estimation performance of single-photon LiDAR in complex scenes. 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

Tantalum pentoxide (Ta₂O₅) has emerged as a versatile material at the intersection of optical coatings and integrated photonics because it combines a high refractive index, a wide bandgap, low optical loss, and compatibility with multiple thin-film deposition routes. Over the past decade, the literature has expanded from conventional dielectric coating studies to low-loss waveguides, micro-ring resonators, wavelength conversion, and broadband supercontinuum generation, while more recent work has increasingly emphasized defect engineering, nonlinear absorption, and laser damage reliability under strong optical fields. The objective of this review is to establish a process–structure–composition–property–function–reliability framework for understanding Ta₂O₅ and non-stoichiometric Ta₂O_5−x optical coatings in high-power photonics. Unlike previous reviews that mainly emphasized dielectric properties, deposition methods, or general thin-film applications, this review highlights how deposition-induced composition changes, oxygen vacancy-related defects, nonlinear optical response, and laser damage reliability jointly determine the operational limits of tantalum oxide photonic materials. Particular attention is given to ion-assisted and ion gun-assisted processes, which have repeatedly been associated with higher film density, smoother morphology, reduced oxygen vacancy-related loss, and more stable high-field behavior. By linking coating-level process control to device-level functions such as four-wave mixing, self-phase modulation, wavelength conversion, and supercontinuum generation, this review highlights how thin-film engineering governs both optical performance and operational limits. It also identifies several persistent gaps, including the need for standardized reporting of nonlinear absorption, unified damage metrics across film and device geometries, and stronger correlations among microstructure, composition, defects, and long-term optical stability. Overall, this review provides a composition-aware and coating-informed framework for interpreting Ta₂O₅ photonics and a practical roadmap for developing durable high-power photonic components. Full article

Today, the rapid progress in non-invasive light–matter interaction analysis is transforming the landscape of biomedical and life sciences driven by low-intensity light detection technologies. As the complexity of photonic applications continues to grow, the importance of single-photon detection techniques becomes pivotal. Among them, Time-Correlated Single-Photon Counting (TCSPC) has become the gold standard for precise, time-resolved reconstruction of rapid and faint optical signals. However, TCSPC has long been constrained by pile-up distortion, which worsens with increasing acquisition speed, typically limiting it to 5% of the excitation frequency. To overcome the operational constraints of conventional implementations, a novel TCSPC acquisition methodology has been introduced, independent of photodetector dead time, excitation intensity, and prior optical signal knowledge, still enabling distortion-free reconstruction of the measured light profiles. In this context, the development of single-photon detectors with short dead time and low timing jitter becomes crucial. This work presents a single-photon detection module based on a Silicon Photomultiplier, which delivers 750 ps FWHM output pulses with a 33.5 ps RMS IRF. Its performance is showcased through fluorescence measurements employing the constraint-free TCSPC methodology, achieving a photon count rate up to 166% of the excitation frequency with a minimal lifetime estimation error of just −1.46%. Full article

Feedback delays and the coexistence of multiple timescales are central features of complex dynamical systems, ranging from neural networks and ecosystems to electronic and optical devices. Interactions between fast and slow dynamics can give rise to rich emergent behaviors that are absent in single-timescale systems. Here we investigate how these coupled timescales shape the dynamics of a photonic neuron with single and dual delayed feedback. Using ordinal pattern analysis and recent ordinal-based complexity measures, we characterize the temporal correlations and symmetry properties of the fast peaks and slow spikes generated by the system. Our results show that the signatures of determinism exhibited at fast and slow timescales differ markedly, revealing a strongly multiscale organization of the dynamics. Despite these differences, when represented in the symmetry-based $\mathsf{\Phi }$-space, all cases, fast peaks and slow spikes under both single and dual feedback, collapse onto a common curve. This universal structure indicates the presence of underlying constraints governing the system’s dynamics across temporal scales and feedback configurations. These results highlight the power of ordinal-based approaches to uncover hidden symmetries and multiscale organization in delayed nonlinear systems. Full article

Electrochemical exfoliation is an efficient approach for producing MoS₂ nanosheets, yet the correlation between exfoliation conditions, structural evolution, and nonlinear optical (NLO) properties remains insufficiently understood. In this work, MoS₂ nanosheets were prepared using two representative electrolyte systems, acetonitrile/TPABr and aqueous Na₂SO₄, under controlled voltages. The results reveal distinct exfoliation mechanisms, where ion intercalation dominates in the nonaqueous system, while bubble-assisted processes prevail in the aqueous system. Structural and chemical analyses (Raman, XRD, EDS, and XPS) demonstrate that the nonaqueous system yields MoS₂ with higher crystallinity and lower oxidation degree, whereas the aqueous system shows increased oxidation with the coexistence of Mo⁵⁺ and Mo⁶⁺ species. Correspondingly, enhanced nonlinear absorption and optical limiting performance are observed. A clear mechanism–structure–property relationship is established, highlighting the critical role of electrolyte environment and applied voltage in tailoring NLO responses. This work provides insights into the controlled preparation of MoS₂ nanosheets for photonic and optoelectronic applications. Full article

In this paper we study photon entanglement in the framework of Maxwell–Schwartz field theory. The ambient state space is the complex Maxwellian distribution space $W={\mathcal{S}}^{\prime }({\mathbb{M}}_4,{\mathbb{C}}^3)$, whose elements are fields of the form $F=\overrightarrow{E}+ic\overrightarrow{B}$. Polarization is realized as a two-dimensional complex subspace of W, generated by suitable linearly polarized Maxwellian solutions associated with opposite propagation directions. This yields canonical polarization sectors $P_A$ and $P_B$, each naturally isomorphic to ${\mathbb{C}}^2$. Within this setting, the Bell singlet state is represented by a non-factorizable tensorial Maxwellian field in $P_A\otimes P_B\subset W\otimes W$. By means of the induced rotated polarization bases, the standard joint probabilities of the photon polarization experiment are recovered exactly, and the correlation law $E(a,b)=-cos\left(2\right(a-b\left)\right)$ is obtained. Consequently, the usual CHSH value $2\sqrt{2}$ is reproduced in the Maxwell–Schwartz framework. To clarify the meaning of this violation, we first formulate the CHSH inequality in a purely measure-theoretic form, as a theorem about four correlators represented on a single probability space by bounded measurable functions. We then show that the correlators produced by the intrinsic Maxwellian Bell state do not admit such a common representation. The obstruction is structural: the ontic state is a global non-product field configuration, and the four correlations arise from different polarization resolutions of the same tensorial Maxwellian state. A second main result concerns the Born rule. For $L^2$ scalar quantum states in the domain of the Maxwellian correspondence, we prove that the squared Hilbert norm, times the constant ${\epsilon }_0$, coincides with the electromagnetic energy of the associated field. This leads to an energy interpretation of the Born rule: the Born probability density is identified with the normalized electromagnetic energy density up to an interference term depending on the chosen Maxwell–Schwartz isomorphism, which assumes the role of a quantum context. In the context of the Aspect and collaborators’ experiment, we prove that, on the other hand, the polarization probabilities become energy contributions of the corresponding field components. These results show that photon entanglement, Bell inequality violation, and the Born rule admit a coherent interpretation within Maxwell–Schwartz field theory, where the basic ontological objects are electromagnetic-like fields rather than abstract state vectors. Full article

Three ethynyl-extended benzanthrone derivatives with benzonitrile (Dye A), thiophene (Dye B), and methyl propiolate (Dye C) as substituents were synthesized and investigated to illustrate structure–property relationships governing their nonlinear optical (NLO) behavior. The third-order nonlinear absorption and refractive index of three dyes were studied using open- and closed-aperture z-scan measurements under 532 nm continuous-wave laser excitation. All dyes exhibited reverse saturable absorption dominated by two-photon absorption, with Dye A showing the highest nonlinear absorption coefficient (βeff = 2.3 × 10⁻⁵ cm/W) and two-photon response, attributed to its extended conjugation and smaller HOMO−LUMO gap (6.45 eV). Closed-aperture Z-scans revealed strong nonlinear refraction (n₂), with the thiophene-substituted Dye B displaying the largest n₂ (14.8 × 10⁻⁹ cm²/W) and third-order susceptibility (χ³ = 3.1 × 10⁻⁶ esu). The evaluated optical switching figures of merit met the requirements for all-optical switching and optical limiting. DFT and TDDFT calculations demonstrated that donor substitution and conjugation length govern electronic structure, charge transfer character, and global reactivity descriptors. Enhanced electronic softness and hyperpolarizability in Dye B further support its superior refractive nonlinearity. These results establish clear structure–property correlations and highlight donor engineering as an effective strategy for developing organic nonlinear optical and photonic materials. Full article

Underwater gated time-correlated single-photon-counting (TCSPC) LiDAR is advantageous when weak target echoes coexist with strong backscatter. However, under the first-photon-triggering and SPAD dead-time mechanism, the estimated time of flight becomes dependent on the return strength, thereby producing a range walk error (RWE). This paper develops a condition-calibrated correction framework for accumulated-histogram underwater ranging in the low-photon regime. A non-homogeneous Poisson first-arrival model that jointly includes gate-limited signal photons and in-gate background triggering yields a computable expression for the total trigger probability and the conditional first-arrival time. A first-order expansion around $N_{pe}\approx 0$ leads to an approximately linear RWE–$N_{pe}$ relation under the present system–water condition. A density-based signal-window localization method and a noise-occlusion-compensated estimator of $N_{pe}$ are combined with reference-plane differential calibration. Experiments in a 10 m clear-freshwater tank at 9.11 m show that the mean absolute error is reduced from 39.205 mm to 2.130 mm, corresponding to a 94.57% improvement. Compared with a quadratic model used under higher-photon conditions, the proposed linear model yields an order-of-magnitude smaller residual error in the low-photon region ($N_{pe}<1.6$). Full article

Conventional tests of Bell’s inequality rely on entangled photon pairs. Here, we replace entangled pairs with two independent photons of orthogonal polarization and demonstrate that Bell’s inequality is still violated. Given the inherent local realism of independent photons, this experiment proves that Bell’s inequality cannot falsify the local realism of photons. We thus conjecture that the violation of Bell’s inequality by entangled photon pairs originates from their orthogonal polarizations rather than the breakdown of local realism. To interpret this unexpected violation with independent photons, we further substitute the two photons with two monochromatic light beams and calculate the transmittance correlation through polarizers via Malus’s law and Karl Pearson’s correlation formula. We show that this correlation also defies Bell’s inequality. Retracing the derivation of Bell’s inequality reveals that its validity is restricted to binary events, which accounts for the observed violation with light beams. Finally, we propose a thought experiment involving the gradual attenuation of light intensity down to the single-photon regime and hypothesize that single-photon transmission through a polarizer does not constitute a binary event. This hypothesis provides a unified interpretation for both our experimental findings and all canonical Bell inequality tests reported to date. Full article

Detection of trace gases with high sensitivity and weak excitation power is highly desired for long-range remote sensing. Here, we report the detection of the greenhouse gas nitrous oxide (N₂O) with the power of excitation light down to picowatts, by converting the mid-infrared laser to near-infrared photons through an intra-cavity-enhanced sum-frequency upconversion system. The intra-cavity-enhanced pumping power of 1064.0 nm reaches about 200.0 W, resulting in the conversion of the 4514.6 nm mid-infrared laser to 861.1 nm with an efficiency up to 73.4% under optimal conditions. The upconverted light is then detected by a single-photon avalanche detector, followed by a time-correlated single-photon counting module, which can measure the arrival time of each upconverted photon. By performing discrete Fourier transformations of the arrival time of the detected photons, the frequency spectrum can be determined. By using frequency modulation, this method can suppress background noise significantly. Consequently, the excitation power can be brought down to about 100 pW with the concentration of N₂O being 10 ppm. As a demonstration of application, the presented system is also used for N₂O sensing in an open-path geometry, highlighting the potential for stand-off leak detection. Our proposal offers promising applications to monitor trace gases over long distances with weak excitation powers. Full article

Spaceborne LiDAR systems, such as ICESat-2, provide critical data for global land cover and topography; however, their performance in rugged, vegetated landscapes requires rigorous local validation. This study evaluates the vertical accuracy of ICESat-2 ATL08 terrain height metrics in the complex Turkish Western Black Sea region, utilizing a reference dataset of high-precision terrestrial GNSS measurements. Following strict IQR-based outlier detection and photon density filtering, 1637 spatially matched segments were analyzed. The h_te_best_fit terrain height metric showed the best agreement with the terrestrial GNSS reference data, yielding an RMSE of 3.37 m and a mean bias of −0.42 m, indicating a slight underestimation of the terrain surface. The univariate analysis revealed a strong positive correlation between terrain slope and vertical error, indicating that slope is the prominent degradation factor contributing to pulse broadening. Additionally, dense forest cover was found to limit ground photon retrieval, leading to increased error margins, whereas nighttime acquisitions offered slightly improved precision. These findings suggest that while ATL08 is a valuable topographic source, slope-dependent corrections are essential for applications in mountainous environments. Full article

Geometrical and structural disorders are inevitable in fabricated photonic structures and can significantly impact their optical performance. Here, we investigate the robustness of perfectly nonreciprocal diffraction (PND) against these two types of disorder in one-dimensional (1D) atomic lattices. The significantly distinct diffraction phenomenon can be uncovered when the optical lattices introduce controlled random perturbations into the geometrical and structural parameters of each lattice site. Our results demonstrate that the forward diffraction spectrum exhibits remarkable resilience to both disorder types. Conversely, the backward diffraction spectrum is highly sensitive, displaying distinct responses to uncorrelated and correlated disorders. Specifically, PND persists only below a critical strength for uncorrelated geometrical disorder but is well preserved under correlated geometrical disorder. In stark contrast, PND shows strong robustness against uncorrelated structural disorder yet is significantly degraded by its correlated counterpart. These contrasting phenomena are attributed to whether the disorder introduces random spatial phase shifts that disrupt the destructive interference underlying PND. Our findings provide fundamental insights into wave transport in disordered potentials and offer a pathway for designing robust nonreciprocal devices resilient to fabrication imperfections. Full article

Consciousness presents a structural puzzle: a unified, context-sensitive, globally integrated mode of experience emerging from distributed neural dynamics. While classical neuroscience has mapped synaptic, oscillatory, and network-level mechanisms with increasing precision, debate persists as to whether classical formalisms fully capture the integrative and contextual features of conscious processing. This review examines whether quantum principles offer explanatory leverage in two distinct senses: as formal mathematical frameworks for modeling contextual cognition, and as mechanistic hypotheses proposing biologically instantiated non-classical states. We surveyed empirical and theoretical developments spanning zero-quantum-coherence in MRI signals, entanglement-structured learning paradigms, quantum-inspired computational models, and proposed neural substrates, including microtubules, nuclear spins, and photonic architectures. Although certain findings have been interpreted as consistent with a non-classical structure, no study to date has demonstrated entanglement, long-lived coherence, or collapse dynamics in neural tissue under operational criteria comparable to those used in controlled quantum systems. Replication remains limited, biological entanglement witnesses are not yet established, and nonlinear classical dynamics can reproduce many putative quantum signatures. Accordingly, the decisive question is not whether the brain is quantum, but whether its dynamics exceed the explanatory reach of rigorously defined classical models. Progress hinges on replication, adversarial scrutiny, and operational criteria precise enough to discriminate genuine non-classical correlations from classical complexity. Whether quantum mechanisms ultimately prove necessary or refined classical models remain sufficient, this inquiry compels a deeper understanding of integration, contextuality, and the physical constraints shaping conscious experience. Full article