Light scattering constitutes the most fundamental process in light-matter interactions and serves as the cornerstone of modern particle metrology. Although numerous scattering-based techniques have been established for characterizing particles in constrained motion, the precise analysis of freely flying particles remains largely underdeveloped. This limitation stems primarily from the severe constraints on accessible data acquisition time and the motion-induced image blur inherent in conventional scattering detection schemes. Here, we report the observation of a Doppler-encoded Mie scattering effect using optically propelled microparticles in antiresonant hollow-core fibers and further introduce a transverse Doppler spectrometry for single-particle-level metrology of flying particles. It is found that, when collected in the near field by a high–numerical aperture objective, the scattering fringes of a flying particle with divergent diffraction angles are encoded with distinct Doppler frequency shifts—this forms a broadband “scattering rainbow” in the transverse direction relative to the incident beam axis. This angle-dependent Doppler effect transforms the spatial diffraction pattern of a flying particle into the frequency domain, enabling high-precision determination of diameter and refractive index of airborne particles within a millisecond-scale observation window. Our findings unlock degrees of freedom for resolving flying particle features in the frequency domain, establishing a versatile diagnostic platform for a broad spectrum of applications that demand in situ particle analysis, such as atmospheric aerosol monitoring, hypersonic flow diagnostics, and label-free flow cytometry.

Fiber endoscopicimaging system exhibits high-precision imaging capability in extreme scenarios due to its flexibility and compatibility. The fiber bundles are naturally suitable to collect 2D intensity information, but it is difficult to directly obtain depth or angle information. Therefore, a large number of complex optical components are usually required to achieve dual-function imaging. In this work, we propose a single round-trip system with metasurface-integrated fiber bundle, namely the so-called Janus metafiber system. With the forward and reverse switching of the same optical path, we simultaneously achieving passive 2D imaging in the visible regime and active 3D depth sensing. The experiment shows high imaging fidelity and noise resilience benefiting from time-division acquisition between single-wavelength array scanning and polychromatic illumination. Especially, a 60° FOV and a divergence angle less than 2° has been verified in the interpolation optimized 3D depth imaging. Furthermore, the enhanced broadband depth-resolved synthetic imaging and edge detection are demonstrated combining the bimodal data. Our work enlightens potential applications in real-time biomedical diagnostics, LiDAR, and industrial inspection.

Predictive modeling of total pressure loss in a high-speed SI engine exhaust manifold: Influence of penetration length and divergence angle

Laser optoelectronic transceiver systems are widely used in space, aviation, and ground platforms. Accurate control of focal positions in the terminal optical path is critical for energy concentration and imaging quality. Conventional laboratory focusing methods use large-aperture, long-focal-length collimators or star-point targets. These systems are bulky and difficult to deploy with the terminal. After environmental tests, they hardly support refocusing calibration or quantitative evaluation of transmitter defocus and divergence. To address these issues, a Gaussian-beam-based alignment and calibration method is proposed. The method enables camera focusing and the measurement of the object-side defocus and beam divergence angle of the transmitting fiber collimator, while a corresponding theoretical model is established. It employs a fiber collimator with fixed divergence. Gaussian spot profiles are fitted within a limited space, which allows high-accuracy quantification of focal length and object-side defocus. Simulation and experimental results consistently confirm the effectiveness of the proposed approach. Compared with the collimator-based focusing method, the mean focal length is closer to the nominal value. The maximum relative error of the focal length is reduced by about 81.3%, and the root-mean-square deviation is reduced by about 80.7%. The deviations of object-side defocus and divergence from theory are within 2%. The method has a compact structure and modest calibration requirements. It is suitable for terminal alignment, recalibration, and focus inspection under static or quasi-static conditions, and provides an effective technical approach for high-precision, miniaturized, and scalable engineering implementation of focusing.

Numerical simulation on the influence of divergence angle of conical nozzle on flow field characteristics of submerged cavitating jet

Lasers typically exhibit many advantages over conventional light sources, including the ability to produce monochromatic laser beams, small divergence angles, excellent coherence, and high output power. Therefore, investigating the application of laser ignition/initiation properties in the field of energetic materials is of great significance. In this study, two energetic coordination compounds (ECCs) were successfully synthesized: [Pb(Az-BTz)(H2O)3]n, referred to as ECC-1 in this work, and [Pb(Az-BTz)(NO3)(H2O)2]n, referred to as ECC-2, where Az-BTz denotes 1,2-di(2'H-[1,5'-bitetrazol]-5-yl)diazene. Although ECC-1 shows a more pronounced red-shifted light absorption than ECC-2 does due to π-π stacking and charge transfer effects, it ultimately underperforms in practical applications because it fails to cover the widely adopted 808 nm band. By contrast, band structure calculation results indicate that ECC-2 features a narrower energy band gap, which significantly improves its light-to-heat conversion efficiency. Despite ECC-2 exhibiting relatively lower thermal stability than ECC-1─thus making it more susceptible to thermal initiation─this drawback is offset by its superior overall performance. Ultimately, laser initiation experiments further confirm the effectiveness of ECC-2, which demonstrates an impressive initiation time of 1.02 ms and an initiation energy below 5 mJ.

A polygonal microcavity 9 μm quantum cascade laser (QCL) incorporating an output waveguide and a master oscillator-power amplifier (MOPA) configuration is proposed and numerically investigated to overcome the inherent trade-off between directional emission and beam quality in long-wavelength infrared (LWIR) microcavity lasers. The active region of a 9 µm InP-based QCL is designed using Nextnano to achieve wavelength-matched optical gain, while the coupling characteristics between the polygonal microcavity and the MOPA waveguide are systematically optimized using Ansys Lumerical. Finite-difference time-domain simulations are performed to examine the influence of key structural parameters, including the flare angle of the power amplifier, the length of the master oscillator section, and the amplifier cavity length, on the output intensity, slow-axis divergence, and diffraction behavior. The results indicate that an appropriately flared amplifier enables effective transverse mode reshaping, leading to significant suppression of higher-order diffraction and pronounced reduction of slow-axis divergence while preserving the resonant properties of the microcavity. The master oscillator length is found to mainly affect the phase distribution at the output facet, with a limited impact on the divergence angle. An optimal amplifier length exists that simultaneously enhances beam quality and output performance. These findings provide a practical design strategy for realizing a high-power, high-beam-quality, and integrated long-wavelength infrared microcavity QCL.

The polarization control and coherence of thermal emission are crucial for enhancing its application performance. However, existing solutions primarily rely on supercell expansion or periodic perturbation to introduce band folding, which complicates the structure, reduces fabrication tolerance, and complicates dynamic control. This study proposes a method for regulating thermal emission based on magneto-optical photonic crystals. By introducing periodic anisotropy in the orthogonal directions of the lattice, a saddle-shaped band that can be tuned by magnetic fields is naturally formed in the terahertz frequency range. This process does not require supercell expansion or periodic perturbation and can achieve strong anisotropic dispersion solely through periodic regulation at the single-cell scale. By introducing magnetic optical materials and applying an external magnetic field, the active control of chirality and polarization state was achieved, and the full polarization-switchable thermal radiation from linear polarization to circular polarization was accomplished. Numerical results demonstrate that this structure can achieve circular dichroism exceeding 0.985, a quality factor exceeding 500, and a radiation divergence angle of less than 0.75°, while exhibiting good robustness to perturbations in key geometric parameters. This work provides an approach for realizing a dynamically reconfigurable, structurally simple, and highly coherent terahertz polarization thermal radiation source.

ABSTRACT Satellite communication fulfills the demand of global connectivity for next‐generation networks. Free space optical (FSO) communication connects these high‐bandwidth global links for seamless transmission. High altitude platform station (HAPS) improves the outage probability by relaying the signal when transmission to the long distances in one hop is not reliable. In this work, we consider adaptive beam divergence (ABD) technique for a low earth orbit (LEO) satellite, which transmits the FSO signal to the HAPS, where the divergence angle of the signal is selected based on the altitude of the HAPS. We considered the effects of threshold signal‐to‐noise ratio (SNR), receiver aperture diameter, jitter standard deviation, optical‐to‐electrical conversion efficiency and the horizontal distance between satellite and HAPS on the link outage probability. The results show that by using an appropriate beam divergence angle according to the height of the HAPS, the performance of the system improves. Additionally, it is observed that for a fixed outage probability, ABD achieves communication for longer transmission range with the HAPS located at an altitude, which is lower in comparison with the altitudes at lower and upper fixed divergence angles by 1.610 and 2.169 km, respectively.

Design and simulation of ellipsoidal single-bounce mono-capillary condensers for a laboratory X-Ray nano-imaging system.

We demonstrate room-temperature pulsed lasing of two types of GaN-based surface emitting lasers (SEL) fabricated without epitaxial regrowth. We present a direct comparison between a circular grating (CGSEL) and a photonic crystal (PCSEL) design. The devices are realized by etching the photonic structures directly into the p-GaN cladding, and utilizing a patterned indium tin oxide (ITO) top contact. Both designs exhibit lasing near 438 nm under pulsed current injection. The CGSEL, incorporating a central defect, achieves a low threshold current density (<1 kA/cm2) and a small divergence angle (≈0.15°) by coupling to a bandgap defect mode. In contrast, the PCSEL shows a higher threshold current density and lases on a 1D band-edge mode, resulting in a cross-shaped far-field pattern. These results confirm the regrowth-free method as a viable route for manufacturable GaN SELs. Crucially, the comparative study identifies the CGSEL defect-mode design as a more robust path toward high-performance lasing in low-confinement epitaxial structures.

Quasi-non-diffraction beam plays an important role in suppressing the divergence angle of the vortex electromagnetic wave. In this paper, a circular Pearcey beam is applied for orbital angular momentum (OAM) vortex beam’s divergence angle suppression, and a quasi-non-diffraction circular Pearcey vortex beam is generated with a transmission metasurface in the millimeter wave band. A full design method of the quasi-non-diffraction circular Pearcey vortex beam is proposed, and it is discussed in detail. An amplitude and phase controllable transmission metasurface working at 30 GHz is designed to generate a quasi-non-diffraction circular Pearcey (QCP) vortex beam with OAM mode of l = + 1. The simulated circular Pearcey vortex beam exhibits a distinct quasi-non-diffraction characteristic. Moreover, the circular Airy vortex beam and the conventional OAM vortex beam are also simulated and analyzed to compare with the designed Pearcey vortex beam. To further validate the proposed method, the designed transmission metasurface is fabricated and measured, and the measurement results align well with the simulation.

We propose and experimentally demonstrate an eight-channel high-power distributed feedback–semiconductor optical amplifier (DFB–SOA) master oscillator–power amplifier array with 100 GHz wavelength spacing for optical input/output (I/O) applications. The gratings are fabricated using the reconstruction equivalent chirp technique to simplify the fabrication process and enhance wavelength control accuracy. An equivalent π phase shift is introduced at 1/5 of the cavity length near the HR facet to enhance the single-mode yield. The slab-coupled optical waveguide structure is employed to reduce internal loss, increase output power, compress linewidth, and support single-transverse-mode operation. Each DFB laser is integrated with a dedicated SOA to enable independent power amplification and channel equalization. High-reflection (HR) and anti-reflection (AR) coatings are deposited on the rear and front facets, respectively, to further enhance the output power. Experimental results show that the eight-channel array achieves precise wavelength control and excellent single-mode characteristics, with an average wavelength spacing of 0.798 nm, side-mode suppression ratios (SMSRs) above 60 dB, and a wavelength deviation of 0.002 nm from the design value. At a bias current of 600 mA for both the DFB and SOA, the output power exceeds 300 mW per channel. The measured Lorentzian linewidth is below 300 kHz, the relative intensity noise is lower than −145 dB/Hz, and the far-field full-width at half-maximum divergence angles are 11.6° × 31.4°. The proposed array demonstrates outstanding performance as a multi-wavelength light source for high-power, high-coherence optical I/O systems.

To enhance the far-field beam quality of the optical phased array (OPA) chip, this paper proposes what we believe is a novel OPA coherent combining architecture based on inter-chip interference. In this architecture, phase modulators are employed for inter-chip phase control, with their half-wave voltages serving as critical parameters for achieving high-precision phasing. To address the low-frequency (DC-kHz) phasing requirements in OPA coherent combining, a half-wave-voltage measurement method is proposed, based on which closed-loop coherent combining of two OPA chips is realized. Experimental results demonstrate that the far-field beam can be stably combined into a single-main lobe, with the divergence angle reduced from 0.181° to 0.066°. This significantly enhances beam quality, validating the effectiveness of the proposed architecture and measurement method.

ABSTRACT A method for generating dual high‐order orbital angular momentum (OAM) modes by integrating spoof surface plasmon polariton (SSPPs) and spoof localized surface plasmon (SLSPs) is proposed. The proposed design consists of N rotationally arranged SSPP waveguides periodically loaded with SLSP patches, which enables broadband circularly polarized (CP) radiation and introduces a dynamic phase. Unlike conventional approaches that rely on excitation phase control and complex feeding networks, the proposed method utilizes dynamic and geometric phases to synthesize the required phase distribution for high‐order OAM modes, thereby eliminating the need for phase‐shifting networks. Moreover, exploiting the leaky‐wave theory, dual high‐order OAM modes with l = − N + 1 and l = N + 1 are generated by varying the frequency to alter the dynamic phase. The experimental results confirm that the proposed device is capable of generating high‐order l = −7 and l = +9 OAM modes at 9.7 and 13.0 GHz, with gains (divergence angles) of 8.4 dBic (33°) and 5.6 dBic (23°), respectively. This work provides a phase‐network‐free solution for dual high‐order OAM generation with frequency‐controlled mode switching, demonstrating potential for applications in sensing, radar detection, and mode‐division multiplexing systems for wireless communications.

This study presents an innovative design methodology for abrasive nozzles that integrates multi-software collaborative simulation with multi-objective optimization, aiming to significantly improve the overall performance of abrasive jet cleaning. A coupled CFD-DEM numerical model was developed to systematically investigate, for the first time, the inherent influence mechanisms of critical nozzle structural parameters—including throat diameter, contraction length, divergence angle, and total length—on both abrasive jet uniformity and nozzle wear resistance. Through response surface methodology, a multi-objective optimization model was constructed and solved, yielding an optimized nozzle configuration with an inlet diameter of Ф25 mm, throat diameter of Ф14 mm, divergence angle of 8°, and total length of 215 mm. Experimental validation confirmed that this optimized design synergistically enhances performance, achieving a 22.00% increase in abrasive jet core coverage while reducing maximum nozzle wear by 44.62%. Furthermore, this research establishes a multi-software integrated simulation and optimization framework, termed the “FLUENT–EDEM–MATLAB–ORIGIN–DESIGN-EXPERT” workflow, which provides a robust methodological paradigm with considerable engineering relevance for the design of high-performance gas–solid two-phase flow nozzles.

This work proposes and fabricates a loss-enhanced supersymmetric semiconductor laser. By introducing a loss-enhanced slot (LE-slot) into the supersymmetric waveguide arrays, additional loss is imposed on photons propagating within these arrays, thereby increasing the lasing threshold of the corresponding modes. Consequently, a small horizontal far-field (HFF) divergence angle is maintained even at high injection currents. The laser achieved a quasi-single-lobed horizontal far-field distribution at an injection current of 0.5 A with an output power of 200 mW. At a current of 1.5 A, it delivered an output power of 692 mW while maintaining a HFF divergence angle full width at half maximum (FWHM) of 1.5°. This value exhibits a significant advantage compared to the HFF divergence angle FWHM of a supersymmetric laser without a LE-Slot, which is 5.97° at the same current and 2.97° at a comparable output power level.

Sex determination from skeletal remains is a crucial step in forensic identification, particularly in cases involving incomplete or fragmented remains such as those encountered in mass disasters. Among skeletal elements, the mandible is frequently preserved due to its high resistance to environmental damage. The mandible is the largest and the most robust bone of the facial skeleton. It provides attachment for major masticatory muscles. Mandible also displays distinct morphological traits that are valuable for sex determination. Several non-metric mandibular features have been reported to demonstrate sexual dimorphism. However, the predictive accuracy of these traits varies considerably among different populations due to genetic, functional, and environmental influences. Moreover, studies investigating non-metric mandibular characteristics in the Indonesian population remain limited. Therefore, this study aimed to analyse nonmetric mandibular characteristics in adult Indonesian individuals and evaluated their effectiveness for sex determination. A cross-sectional study was conducted on 49 mandibles of adult (30 males and 19 females) from an Indonesian population. Eight non-metric parameters were observed, including chin shape, chin profile, mandibular ramus shape, mandibular ramus profile, posterior mandibular ramus flexure, gonial angle divergence, muscle marking, and the presence of antegonial notch. Statistical analysis was performed using appropriate software, SPSS version 22.0. The frequency of occurrence of each variable was calculated. Sexual differences were analysed using the Chi-square test and the significance level was set at p&lt;0.05. Then, discriminant function analysis was performed to assess the combined predictive accuracy of the significant traits. As a result, four morphological traits demonstrated significant sexual dimorphism, including chin shape (p&lt;0.05), posterior mandibular ramus flexure (p&lt;0.001), gonial angle divergence(p&lt;0.001), and muscle markings (p&lt;0.001). Based on the discriminant function analysis, the accuracy of prediction for sex determination was 86.7 % in males and 78.9 %, in female, with the overall total predictive accuracy was 83.7 %. The obtained data emphasize that several nonmetric morphological mandibular traits include chin shape, posterior mandibular ramus flexure, gonial angle divergence, and muscle markings, demonstrate marked sexual dimorphism and can therefore serve as an initial approach for sex determination in Indonesian population. The combined assessment of multiple non-metric features improves predictive accuracy and offers a practical screening tool in forensic context, particularly when skeletal remains are incomplete or fragmented.

This research focuses on determining the optimal parameters for maximizing dissolved oxygen (DO) when using a Venturi-type aerator, considering two objectives: oxygen transfer coefficient corrected to 20°C (KLa20) and standard aeration efficiency (SAE). The determination of the optimal parameters for the Venturi-type aerator was carried out under thirty experimental conditions of a face-centered central composite design (FCCD), involving four influencing variables: Venturi convergence angle (α), Venturi divergence angle (β), water flow rate (Qw), and air flow rate (Qa). Response surface methodology (RSM) was used to evaluate the experimentally collected data. The analysis of the experimental results showed that the most suitable conditions for were 45° convergence angles and 15° divergence angles, with a water flow rate of 40 L/min and an air flow rate of 0.9 L/min, resulting in a value of 4.278 h-1. For optimal SAE values, the study found that the Venturi convergence angle of 45°, the Venturi divergence angle of 15°, the water flow rate of 20 L/min, and the air flow rate of 0.9 L/min should be set. These parameters gave an SAE value of 0.0343 kgO2/kWh. Analysis of the regression equations developed in this study showed that the coefficients of determination (R2) of the KLa20 and SAE prediction equations were more than 90% for both equations. Therefore, the response can be accurately predicted, and these equations serve as guidelines for the design of the most appropriate Venturi-type aerator in practice.

Photonic-crystal surface-emitting lasers (PCSELs) are a new type of semiconductor laser with the potential for high-power output and high-beam-quality operation. Integrating a distributed Bragg reflector (DBR) into PCSELs can significantly enhance device performance. However, the growth of high-aluminum-content DBRs on photonic crystal layers with buried air holes presents two major challenges. First, the low mobility of aluminum atoms increases the propagation of surface roughness from the substrate into the DBR, increasing defect density. Second, the high growth temperatures required for DBR growth can deform the thermally unstable air holes. In this work, we investigated a metal–organic chemical vapor deposition (MOCVD) regrowth process for fabricating DBRs on PCSELs. By adjusting the epitaxial growth temperature and V/III ratio, we effectively controlled the diffusion of adatoms on both the sample surface and inside the holes. As a result, the root mean square (RMS) surface roughness decreased by ~96%, and uniform buried air holes were obtained, with a filling factor of ~ 18.8% and a depth of ~ 270 nm, without significant deformation. Finally, we fabricated a PCSEL device with a DBR structure, exhibiting a beam divergence angle of ~ 0.5° and a peak power of about 0.86 W. This study provides a key process solution for the development of PCSELs with high-quality DBR structures, enabling further improvement in optical output performance.