Search Results (2,453)

Laser beam combining is essential for achieving high-power and high-radiance output. However, atmospheric turbulence induces independent tip–tilt aberrations across discrete sub-beams in laser array systems, which severely degrades the concentration of far-field energy. Traditional wavefront sensing techniques are primarily designed for the continuous wavefront of a single laser and are not directly applicable to laser array, whereas indirect optimization-based methods often suffer from slow convergence and limited real-time performance. To address these limitations, this study introduces a tip–tilt aberration compensation system for laser array propagation based on cooperative beacons with a shared-aperture transmit–receive configuration. The primary innovation consists of a modified Shack–Hartmann wavefront sensor (SHWFS) tailored to a discrete multi-beam layout, which facilitates the direct, independent, and simultaneous measurement of tip–tilt aberrations for each sub-beam. In conjunction with a segmented deformable mirror (SDM), the architecture can facilitate real-time closed-loop correction with high bandwidth and high precision. Numerical simulations of a 7-, 19-, and 37-beam laser array, together with validation experiments utilizing a 30-beam configuration, demonstrate that the proposed approach effectively suppresses tip–tilt error induced by turbulence. After closed-loop correction, the Strehl ratio (SR) increases above 0.92 ($r_0=5\mathrm{cm}$), while the beam quality factor β reduces below 1.37 ($r_0=5\mathrm{cm}$). Furthermore, the system retains performance stability as the number of sub-beams increases, demonstrating the scalability of the proposed method. In contrast to conventional approaches designed for a continuous wavefront, the proposed method offers a feasible approach for a discrete laser array system, providing robust and scalable tip–tilt correction under varying atmospheric conditions. Full article

Wound healing research has advanced through nanotechnology-based delivery systems that enhance the stability and therapeutic potential of bioactive compounds. Resveratrol, a natural polyphenol with antioxidant and anti-inflammatory properties, shows promise for wound healing but is limited by poor bioavailability. This study investigates the efficacy of nano-liposome-encapsulated resveratrol in enhancing skin wound repair in adult zebrafish (Danio rerio). Using a laser-based ablation method, precise full-thickness skin wounds were induced and monitored over 50 days. Resveratrol-loaded liposomes were prepared and orally administered via gavage to facilitate systemic exposure. Compared to the control and blank liposome groups, resveratrol liposome treatment significantly accelerated wound closure, achieving earlier healing milestones (25%, 50%, and 75%). The zebrafish model provided a regenerative platform for real-time evaluation of nanomedicine-based therapies. This study demonstrates the wound healing effects of resveratrol and liposomal encapsulation, offering a targeted, systemically administered strategy for advanced systemic healing and highlighting zebrafish as a valuable model for preclinical regenerative medicine research. Full article

Vertical-External-Cavity Surface-Emitting Lasers (VECSELs) have gained significant attention over the past two decades due to their versatility in a wide range of photonic applications. This review focuses on VECSEL configurations for dual-wavelength emission, highlighting their use in high-resolution spectroscopy, terahertz (THz) generation, and advanced optical communication. We explore recent developments in VECSEL designs, including systems utilizing birefringent crystals for polarization-based frequency separation and configurations with dual-VECSEL chips or dual-gain regions within a single cavity. These two-wavelength VECSELs enable diverse operation modes, including narrow-linewidth, pulsed, multimode, and frequency-converted emission, with high-brightness output, excellent beam quality, and tunable wavelengths. Additionally, the review discusses advancements in dual-frequency VECSELs, with applications in LIDAR systems for environmental monitoring, highly stable optical clocks, and fiber sensors. We examine improvements in cavity design, semiconductor structures, and power stabilization, which have enhanced frequency stability and spectral purity, making VECSELs suitable for precision metrology and sensing applications. Full article

We study a 1D model of a diffraction-mediated self-structuring instability which can occur when a Bose–Einstein condensate is illuminated by a pump laser and its reflection from a single feedback mirror. We carry out a linear stability analysis and, using numerical simulations, investigate the dynamics of the self-structuring process. Two dynamical regimes are identified: one in which the system behaves as a continuous space-time crystal oscillating between two states (one spatially uniform and one spatially periodic) and another where many condensate momentum states are involved and the condensate density develops chevrons which form and disperse quasi-periodically. We show the dependence of the pattern modulation depth and pattern formation time on pump saturation parameter and compare the simulation results with analytical expressions derived from a quantum Hamiltonian Mean Field model. The results show that this system offers a route to the first experimental realisation of the quantum Hamiltonian Mean Field model and of a continuous space-time crystal with a tunable spatial period. Full article

Palm kernel oil is commonly incorporated into plant-based cheeses to mimic the textural and structural properties of animal fats owing to its high saturated fat content. Nevertheless, growing concerns regarding saturated fat consumption have stimulated research into alternative lipid sources for plant-based products. Therefore, this study aimed to evaluate the effects of substituting palm kernel oil with rice bran oil shortening (SRBO) on some selected physical, textural, functional, chemical, fatty acid and microstructural properties of plant-based mozzarella cheese analogs. Five formulations with SRBO levels of 0, 25, 50, 75, and 100% were prepared and their physicochemical properties were analyzed. Increasing SRBO significantly affected color due to natural pigments in rice bran oil. The pH value declined with higher SRBO, likely due to oxidation of unsaturated fatty acids. Texture profile analysis showed increases in hardness, springiness, cohesiveness, gumminess, and chewiness when SRBO was increased from 0% to 100%. Meltability slightly decreased at 25–75% but remained unchanged at 100% SRBO, while stretchability decreased significantly, attributed to β-type fat crystals disrupting protein networks. The work of shear decreased significantly (p ≤ 0.05), indicating improved spreadability attributed to the softer, less-crystalline nature of unsaturated fats compared to saturated fats. Proximate analysis revealed reduced fat content and a shift from saturated to unsaturated fats, notably oleic and linoleic acids, offering potential cardiovascular benefits. Confocal laser scanning microscopy showed denser fat crystal networks and smaller fat droplets at higher SRBO levels, enhancing oil retention and stability. Protein, fiber, moisture, and ash content remained stable across samples. These findings suggested that SRBO could be a functional and health-conscious alternative to palm kernel oil in plant-based mozzarella cheese, improving nutritional quality without compromising texture or functionality. Full article

Background/Objectives: Laryngeal leukoplakia and dysplasia carry a variable risk of malignant transformation. Although microlaryngoscopic excision is standard of care, data on voice function are limited. Multidimensional diagnostics, including the Vocal Extent Measure (VEM), were employed to assess pre- and postoperative status while identifying factors associated with vocal outcomes. Methods: This retrospective cohort included 44 patients with histologically confirmed vocal fold leukoplakia or dysplasia. All underwent cold steel or laser-assisted phonomicrosurgery. Voice assessments were conducted pre- and three months postoperatively, comprising videolaryngostroboscopy, auditory-perceptual evaluation of grade, roughness and breathiness (GRB), self-assessment (Voice Handicap Index, VHI-9i), and objective acoustic-aerodynamic measures. Results: Overall, 57% of patients were active smokers; 73% consumed alcohol. Lesions were mostly unilateral (77%), craniomedially localized (65%), and involved up to one-third of the vocal fold (48%), with impaired mucosal wave (76%). Histopathology revealed mainly hyperkeratosis (52%) and dysplasia (35%). Recurrence rate was 14%, with histology unchanged. Postoperatively, subjective measures showed significant improvements (post- vs. preoperative), with decreased VHI-9i scores (10 vs. 14) and GRB ratings (p < 0.05). Objective measures showed positive trends, including enhanced vocal capacity (VEM 85 vs. 82), stability (jitter 0.6 vs. 0.8%), and aerodynamics (maximum phonation time 18 vs. 15 s). Phonosurgical method, histopathology, and age did not significantly affect voice outcomes; however, higher dysplasia grades and younger age showed trends toward greater VEM gains. Conclusions: Phonomicrosurgical excision of laryngeal leukoplakia and dysplasia effectively preserves or enhances vocal function. The VEM provides a reliable, quantitative complement to established voice diagnostics and should be integrated into standardized assessment protocols. Full article

Despite the growing adoption of Ti6Al4V-ELI made by Laser Powder Bed Fusion (LPBF) in tribologically demanding applications, the influence of hybrid nanoparticle additives on its lubrication behavior under starved contact conditions remains insufficiently explored. The tribological performance of Ti6Al4V was investigated under starved boundary-to-mixed lubrication conditions using engine oil modified with Ag-doped TiO₂ nanoparticles. Double-scan LPBF-fabricated discs were tested in a ball-on-disc configuration against AISI 52100 bearing steel using a TRB³ tribometer. Nanolubricants were prepared by dispersing TiO₂ and Ag–TiO₂ nanopowders with different Ag⁺/Ti⁴⁺ ratios (0.5%, 1.5%, and 2.5%) in SAE 10W-40 engine oil at a constant nanoparticle concentration of 0.05 wt%. Comprehensive physicochemical characterization of the nanopowders and nanolubricants was performed through structural, chemical, optical, morphological, rheological, and stability analyses. Tribological experiments were conducted following a full-factorial design combining three normal loads (5–15 N), three sliding speeds (0.10–0.20 m·s⁻¹), and four lubricant formulations. The steady-state coefficient of friction ranged between 0.281 and 0.359, while the specific wear rate varied from 2.81 × 10⁻⁴ to 4.83 × 10⁻⁴ mm³·N⁻¹·m⁻¹. The contact temperature rise remained relatively moderate, within the interval of 1.9–9.4 °C. Among the investigated formulations, the lubricant containing 1.5% Ag–TiO₂ exhibited the lowest friction coefficient, whereas the formulation with the highest Ag content showed improved stability of tribological performance across the investigated operating domain. These results indicate that Ag-modified TiO₂ nanoparticles are consistent with the formation of protective tribofilms and contribute to the stabilization of friction, wear, and thermal behavior under starved lubrication conditions. ANOVA confirmed that sliding speed and the load–lubricant interaction are the dominant factors governing friction and wear, while normal load controls the thermal response. These findings support the use of Ag–TiO₂ nanolubricants as a viable strategy for stabilizing interfacial behavior in LPBF-fabricated titanium components operating under starved lubrication conditions. Full article

Research into the spatial reshaping of monochromatic laser beams grew significantly in the late 1990s due to improvements in the fabrication of diffractive optical elements. Nowadays, some applications, such as optical coherence tomography, necessitate the use of broadband light beams with a spectral width of hundreds of nanometers. The difficulty in reshaping such spectrally broadened beams lies in the wavelength dependence of the beam shaping process. This paper presents a numerical study of the wavelength dependence of two beam shaping techniques that allow a Gaussian beam to be transformed into a flat-top or doughnut intensity profile in the focal plane of a focusing lens. The first technique is based on the diffraction of an incident Gaussian beam passing through a simple binary diffractive optical element. The second technique can be described as an interferometric method, as it involves the coaxial superposition of two Gaussian beams emerging from a Michelson interferometer. We compared the stability of these two techniques’ ability to reshape the beam versus the spectral bandwidth of the incident Gaussian beam. We showed that the interferometric method is more resilient than the diffractive method to changes in the spectral bandwidth of the Gaussian beam. We also considered the case of a quasi-monochromatic beam delivered by a widely tunable laser and reshaped using the interferometric method, where the dispersion of beam reshaping could be mitigated by two programmable liquid lenses that enable control of the curvature of the Michelson interferometer mirrors. Full article

To investigate the influence of external ambient temperature on the transmission characteristics of laser propagation in an internal channel, a simulation model of laser transmission within a closed channel is established in this study. The model comprehensively considers factors including gas density, refractive index distribution, and thermal deformation of optical components. Based on optical transmission theory, the model is used to calculate the beam drift characteristics and the variation in the Strehl ratio at different temperatures. The results indicate that ambient temperature has a significant impact on beam stability and quality. At low temperature (−30 °C), speckle structures appear in the laser spot, with minor drift along the X direction but obvious negative drift along the Y direction, mainly caused by the sinking of cold air driven by gravity and the refractive index gradient. The beam drift decreases initially with increasing temperature, reaches its minimum at around 10 °C, and then increases gradually as the temperature continues to rise. The Strehl ratio initially increases during the early stage of temperature rise, but diminishes in the high-temperature range due to intensified gas disturbances, enhanced thermal lensing effects, and aggravated mirror surface deformation. Full article

Additive manufacturing (AM) represents a quite interesting technology for manufacturing components of nuclear reactors. This work investigated the microstructural stability of 316 L steel fabricated via Laser Powder Bed Fusion (L-PBF) from room temperature to 650 °C. Despite the reduced susceptibility of the material to sensitization owing to its low carbon content, temperature variations may induce deleterious effects in nuclear safety-critical components. In as-printed condition, the microstructure is not stable and undergoes significant changes induced by thermal cycling up to 650 °C in Mechanical Spectroscopy (MS) tests: the typical melt-pool pattern disappears, a population of equiaxed grains substitutes the original ones elongated in the build direction, the average size of the cells forming a finer sub-structure inside the grains increases, texture changes, and the excess of vacancies induced by the rapid cooling is recovered. Although the current literature reports that the microstructure is stable up to 500 °C, MS results indicate that the aforesaid irreversible phenomena start at a lower temperature (~230 °C). The present results suggest that the microstructure of the printed material must be stabilized through suitable heat treatments before its application in structural components for nuclear reactors. Full article

Electromagnetic leakage through ventilation interfaces is a critical challenge in photonic instrumentation, where laser controllers and photoelectric readout circuits are highly sensitive to external interference. In photonic instruments, enclosure leakage may couple into laser controller and photoelectric readout circuits, degrading optical signal stability and electromagnetic cleanliness. To enable fast shielding assessment at the packaging stage, this paper proposes an improved semi-analytical shielding-effectiveness model for hexagonal honeycomb waveguides used in laser controller enclosures. Within a transmission matrix formulation, finite-conductivity loss is included through propagation constant correction, and inter-cell interaction is represented by an array-based coupling correction. The model captures high-frequency additional transmission effects that are not reflected in simplified independent-cell formulations. Validation against CST full-wave simulations from 1 to 40 GHz demonstrates improved agreement, particularly near cutoff and in the upper-frequency range, with substantially lower computational cost than full-wave optimization loops. Geometry-dependent trends are further quantified to support EMC co-design of ventilation and enclosure structures in photonic and optoelectronic platforms. Full article

Titanium and its alloys are widely used in orthopedic and dental implantology for their corrosion resistance and biocompatibility supporting osseointegration; however, their usage is accompanied by release of wear debris that may induce inflammatory responses. The necessity of formation of multifunctional coatings that accelerate osseointegration and provide long-term mechanical stability of titanium implants remains highly relevant. We propose a new simple and scalable coating method based on the laser shock processing technique, with TiO₂ and SrCO₃ powder mix used as an absorption layer. Our results show that this treatment created an approximately 158.3 ± 35.8 μm thick coating consisting of a mixed SrTiO₃-TiO₂ phase. The hardness of this coating evaluated by Vickers microhardness measurements showed a hardness increase of 3.3 times compared to the initial titanium substrate. Piezoelectric force microscopy (PFM) analysis revealed the presence of a reverse piezoelectric effect in the obtained structure confirming the highly likely successful synthesis of coating impregnated with SrTiO₃. This piezoelectric coating can be readily deposited onto titanium substrates using the proposed method, enabling exploration of potential biomedical applications in future research. Full article

Background: Reactive hyperemia (RH) is used to assess microcirculatory function in vivo and has traditionally been interpreted as a local, ischemia-driven vasodilatory response following arterial occlusion. However, perfusion changes consistently observed in contralateral, non-challenged limbs question the exclusively local nature of RH. Objective: This study aimed to characterize reactive hyperemic responses elicited by subsystolic cuff pressures, below arterial occlusion pressure (AOP), and to investigate their effects on glabrous and non-glabrous skin microcirculation and on global hemodynamics. Methods: Seven healthy women underwent a standardized protocol consisting of baseline stabilization, a 2 min subsystolic cuff inflation (70–80% of resting AOP) in one arm, and a recovery period. Microvascular perfusion was simultaneously assessed in both hands using laser Doppler flowmetry (LDF) on glabrous skin and polarized light spectroscopy (PSp) on non-glabrous dorsal skin. Hemodynamic indicators were continuously monitored using CNAP (Continuous Non-invasive Arterial Pressure) technology. Ipsilateral and contralateral responses were compared across experimental phases. Results: Subsystolic cuff inflation induced significant perfusion changes not only in the challenged limb but also in the contralateral limb, despite the absence of a complete arterial occlusion. Conclusions: These findings confirm the adaptive nature of RH emphasizing the major role for the sympathetic nervous system in glabrous skin. In glabrous (palmar) skin, a similar perfusion profile is shown in both hands but significant differences could only be found in the ipsilateral hand. In contrast, non-glabrous (dorsal) skin demonstrated region-specific increases in perfusion, again evident in the ipsilateral hand, suggesting venous stasis. No changes in global hemodynamic variables were observed throughout the protocol. Further studies in larger, more diverse populations are needed to confirm these observations and refine the mechanistic understanding of reactive hyperemia. Full article

Photothermal therapy is a highly promising non-invasive treatment strategy, but its clinical application is still limited by issues such as insufficient light-to-heat conversion efficiency and potential biological toxicity. To address these challenges, this study employed a biomineralization strategy to synthesize gold nanoflowers (Van@Au₄ NFs) using vancomycin as a template. The synthesized Van@Au₄ NFs exhibited a uniform flower-like morphology with a hydrodynamic diameter of approximately 122 nm. Under 808 nm laser irradiation, this material demonstrated excellent photothermal properties, with a photothermal conversion efficiency of 34.94%, and remained stable after four cold-hot cycles. The introduction of vancomycin effectively enhanced the colloidal stability and photothermal conversion ability of the nanoflowers. In vitro experiments showed that Van@Au₄ NFs had an inhibition rate of 90.8% against Staphylococcus aureus and 95.18% against A549 tumor cells under near-infrared light irradiation. This study constructed an efficient photothermal agent, providing important experimental evidence for in vitro synergistic photothermal treatment of bacterial infections and tumors. Full article

Sensitivity and effective sensing range are core performance metrics of flexible pressure sensors, directly dictating their practical applicability. A key challenge in sensor design is sensitivity degradation with elevated pressure, hindering synergistic optimization of high sensitivity and broad sensing range, while cumbersome electrode fabrication further impedes facile preparation and large-scale deployment of high-performance devices. Herein, this work proposes a novel fabrication strategy for flexible iontronic pressure sensors via direct laser writing (DLW) technology. A controllable ultraviolet laser patterns polyimide substrates to fabricate hierarchical stepped conoid-like microstructural templates, which are transferred to ion gels through reverse molding. The DLW-enabled precise geometric control and hierarchical conical architectures efficiently amplify interfacial contact area variation under pressure, significantly boosting sensitivity. The resultant sensor achieves a high sensitivity of 118.4 kPa⁻¹ and a broad detection range up to 2000 kPa, with fast response/recovery times of 38.4 ms and 47 ms and excellent mechanical stability enduring 2000 loading–unloading cycles at 850 kPa. Multi-scenario physiological signal monitoring validates its accurate capture of laryngeal vibrations and joint movements. This work establishes a straightforward, efficient microfabrication route for high-performance flexible iontronic sensors, accelerating their practical application in wearable health monitoring and related fields. Full article