Search Results (2,323)

The 795 nm wavelength corresponds to the D1 transition of rubidium atoms and is widely used in atomic optical pumping, atomic clocks, magnetometers, and precision spectroscopy. For compact free-space collimation, beam shaping, and efficient fiber coupling, edge-emitting semiconductor lasers with reduced fast-axis (vertical) divergence are highly desirable, yet low-divergence designs at 795 nm remain limited. Here, we propose and demonstrate low-divergence photonic-crystal epitaxy (LD–PC) for 795 nm edge-emitting lasers. By engineering a periodic n-side photonic-crystal stack to place the fundamental vertical mode near the photonic band edge, the vertical mode is expanded while maintaining effective modal discrimination. Narrow-ridge Fabry–Pérot lasers based on GaAsP/AlGaAs single-quantum-well epitaxy were fabricated and characterized. The optimized LD–PC device (3 μm ridge width, 1 mm cavity length) delivers 227 mW at 200 mA with a threshold current of 23 mA, a slope efficiency of 1.28 W/A, and a peak wall-plug efficiency of 55% under continuous-wave operation at 25 °C. The measured far-field divergences (FWHMs) are 7.16° and 18.83° in the lateral and vertical directions, respectively, corresponding to a reduction in the vertical divergence from >40° in the reference structure to <20° with LD–PC. These results validate photonic-crystal epitaxy as an effective route toward compact, high-performance, low-divergence 795 nm semiconductor laser sources for rubidium-based atomic systems. Full article

Soliton molecules offer practical advantages in high-speed optical communication, precision spectroscopy, and micromachining. In all-normal dispersion fiber lasers, group velocity dispersion broadens the pulse duration, hindering the attainment of the nonlinearity dispersion balance essential for soliton molecule formation. Consequently, the generation of soliton molecules in such lasers is a technically demanding task. Here, we report an all-normal dispersion fiber laser, mode-locked via nonlinear polarization evolution (NPE) and Lyot filtering. By adjusting the intracavity polarization, this setup allows direct control over pulse interactions, enabling the generation of stable soliton molecules, soliton bound states, and multipulse states. A spectral modulation period of up to 0.95 nm is achieved. In addition, different types of solitons, such as soliton singlets and soliton molecules in tightly and loosely bound states, are observed. Full article

This paper demonstrates a C-band continuously tunable mode-locked fiber laser based on a carbon nanotube saturable absorber (CNT-SA) and a commercial broadband tunable filter. The laser operates in the C-band with a continuous tuning range of 37.3 nm from 1532.6 nm to 1569.9 nm. The erbium-doped fiber (EDF) has a wide gain range, enabling the laser to achieve ultrafast mode-locking. Meanwhile, the tunable filter offers a broad wavelength selection range. This continuously tunable mode-locked fiber laser features a simple structure and a broad operating wavelength range, making it highly suitable for applications in optical communication, sensing, and laser processing. Full article

Singlet oxygen (¹O₂) is a key mediator in photodynamic therapy (PDT), and its generation and reactivity in biological systems have been extensively studied. It has been shown that laser radiation at near-infrared (NIR) regions can be used to directly generate ¹O₂. In this work, we investigated photosensitizer-free ¹O₂ generation using an original all-fiber pulsed laser operating at 1066 nm and 1241 nm and evaluated its impact on mitochondrial activity in U-87 MG glioblastoma cells. Singlet oxygen was evaluated using the 1,3-diphenylisobenzofuran (DPBF) chemical probe and confirmed with argon-purging controls, demonstrating clear oxygen- and wavelength-dependent effects. Laser irradiation of glioblastoma cells demonstrated distinct effects depending on the wavelength, although decrease in cellular metabolic activity was observed in both cases. Interestingly, some inhibitory effect was also observed when the culture medium was pre-irradiated at 1241 nm and subsequently added to intact cells. These results demonstrate that laser radiation at both studied wavelengths can elicit measurable biological effects, although the relative efficiency in chemical versus cellular systems varies. Collectively, these findings provide a foundation for further systematic studies of wavelength-specific NIR interactions with cellular and molecular components in biological environments. Full article

Parkinson’s disease (PD) is a neurodegenerative disorder caused by the death of dopaminergic neurons in the substantia nigra pars compacta (SNc). Lipid metabolism, especially phospholipids, has been reported to be altered in PD. The purpose of this study is to investigate the temporal expression and spatial distribution of phospholipids in the motor cortex and striatum at different time points of PD using matrix-assisted laser desorption/ionization mass spectrometry imaging (MALDI-MSI) in a 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-induced parkinsonian mouse model. Mice were injected with saline (NSS) or MPTP at two different time points to create acute and subacute models. Motor analysis was performed at 0, 3, 7, 14, and 21 days post-injection. Tyrosine hydroxylase (TH) staining revealed progressive damage of neurons in the substantia nigra compacta (SNc) and reduced striatal fibers in MPTP-treated animals. By using MALDI-MSI, we identified changes in phosphatidylcholine (PC) profiles in the brains of MPTP-treated animals. Polyunsaturated PCs, including PC 36:4 (16:0/20:4), PC 38:6 (16:0/22:6), and PC 40:8 (18:2/22:6), were decreased in the MPTP-treated groups. These reductions were time-dependent and were more pronounced in the subacute MPTP-treated group. The loss of dopamine neurons caused by MPTP may be associated with the selective loss of polyunsaturated PCs in brain membranes, indicating that lipid metabolism and membrane structural alterations may contribute to the pathology of PD. Full article

Background/Objectives: To evaluate the short-term effects of direct selective laser trabeculoplasty (DSLT) on retinal nerve fiber layer (RNFL) and ganglion cell layer (GCL) thickness in patients with ocular hypertension (OHT) and primary open-angle glaucoma (POAG). Methods: This retrospective, single-center study included 45 eyes of 45 patients with OHT or POAG who underwent DSLT at Shaare Zedek Medical Center between February 2024 and February 2025. The primary outcome was the change in RNFL and GCL thickness, as measured by spectral-domain optical coherence tomography (SD-OCT) before and two months after treatment. Secondary outcomes included intraocular pressure (IOP) reduction, corrected distance visual acuity (CDVA), and safety. Only high-quality OCT scans (quality score > 25) were included in the analysis. Results: OCT analysis revealed no statistically significant changes in the inner retinal structure two months post-treatment. The mean RNFL thickness was 77.1 ± 17.2 µm at baseline and 77.4 ± 17.3 µm at follow-up (p = 0.285). The mean GCL thickness remained unchanged (42.4 ± 11.6 µm vs. 42.4 ± 11.3 µm, p = 0.750). CDVA remained stable (0.2 ± 0.4 vs. 0.2 ± 0.4 logMAR; p = 0.351), and no vision-threatening complications were observed. Mean IOP decreased significantly from 19.7 ± 4.0 mmHg at baseline to 16.2 ± 3.5 mmHg at two months (p < 0.001). The mean total laser energy delivered was 196.5 ± 10.2 mJ (range: 176–210 mJ). Conclusions: DSLT was not associated with significant short-term changes in RNFL or GCL thickness, supporting its structural safety in patients with OHT or glaucoma. Further long-term studies are warranted to determine the durability of these findings and the potential neuroprotective effects of DSLT. Full article

Weed management, particularly in organic farming, poses a significant challenge due to high manual labor costs and the crop’s low competitive ability. Precision laser technology offers a promising non-chemical alternative. This study evaluates the field performance of a novel robotic system based on a Thulium fiber laser. The validation was conducted on commercial fields of the Westhof Bio GmbH in Friedrichsgabekoog, Germany. The Weeding Success rate of the laser weeding robot was 95% and the Detection Rate 85% for carrots for one weeding cycle. For beetroot, these values are 98% and 88%, respectively, after two weeding cycles. The field trials validate the Thulium fiber laser system as an agronomically effective and economically viable alternative for sustainable weed management. The technology demonstrates the potential to significantly reduce manual labor and reliance on herbicides in challenging crops. Full article

Background: Diabetic neuropathy manifests as symmetric distal and autonomic neuropathy, including cardiovagal dysfunction. Small-fiber involvement can occur, leading to neuropathic pain and dysautonomia. The diagnostic gold standard of these two conditions comprehends skin biopsy and cardiovascular autonomic reflex tests (CARTs), respectively. Non-invasive diagnostic tools, such as laser-evoked potentials (LEPs), show promise in detecting small-fiber damage, though correlations between LEP abnormalities and cardiovascular autonomic dysfunction remain poorly investigated. Methods: We retrospectively evaluated LEPs (from hands and feet stimulation) in 33 diabetic patients, comparing them to a cohort of 33 age-matched healthy subjects, to highlight any significant abnormalities in the diabetic cohort. We further analyzed the LEP results in T2DM cohort with clinical, laboratory variables and CARTs to explore potential correlations and to assess whether any association between LEPs and CARTs could be identified. Results: N2/P2 complex amplitude was significantly reduced in diabetic patients compared to healthy subjects, with greater involvement in the lower limbs. While no association between LEP abnormalities and abnormal CARTs was observed, LEP amplitude reductions were notably associated with elevated glycated hemoglobin levels and longer disease duration, which appeared to be the strongest predictor of LEP reduction. Conclusions: Our findings corroborated literature data regarding length-dependent LEP alterations detectable even in initial diabetic stages. The lack of correlation between LEP abnormalities and autonomic dysfunction may stem from the predominant involvement of C fibers in autonomic neuropathy, which are not adequately assessed by currently used LEPs. Full article

Dual-frequency lasers with narrow linewidth and high coherence serve as essential light sources for systems such as heterodyne detection, LiDAR, and precision interferometry. However, existing technologies cannot directly separate the two frequency components at MHz-scale differences, which remains a persistent bottleneck in this field. In this paper, we present a dual-frequency fiber laser based on a bidirectional dual-path ring cavity. The proposed laser supports flexible switching between single-frequency and dual-frequency operation while allowing straightforward physical separation of the two outputs via intrinsic beam routing. In single-frequency mode, the two beams exhibit Lorentzian linewidths of 1.1 kHz and 1.16 kHz, respectively. In dual-frequency operation, the laser produces a beat signal at 470 MHz with a 3-dB linewidth of 340.2 Hz and a signal-to-noise ratio (SNR) exceeding 70 dB. This dual-frequency fiber laser provides a novel and practical source for heterodyne detection and LiDAR-based measurement systems. Full article

Background/Objectives: Laser Doppler flowmetry enables rapid and simple measurement of microcirculation. However, variations in probe configuration can influence signal acquisition, making it essential to understand each probe’s characteristics when selecting equipment for specific physiological assessments. Therefore, this study aimed to compare perfusion measurements obtained with single-fiber (VP1T) and multi-fiber (VP1T/7) probes and to evaluate the effects of normalization strategies. Methods: Nine healthy female volunteers were recruited. Probes were positioned on the palmar aspects of the index and middle fingers of both hands while participants underwent a standardized brachial artery occlusion protocol. Data are presented as mean ± standard error of the mean. Correlations were assessed using Pearson’s correlation coefficient. Coefficients of variation (CV) and intraclass correlation coefficients were calculated. Baseline normalization was applied to measurements. Statistical analyses were performed using Student’s t-test, with significance set at p < 0.05. Results: Analysis of the full protocol revealed significant positive correlations between probes, indicating consistent temporal perfusion patterns. The VP1T/7 probe yielded significantly higher perfusion values than the VP1T probe, although both exhibited similar CVs. Inter-probe reliability was good, and intra-probe reproducibility ranged from good to excellent, particularly for the VP1T/7 probe. During the reperfusion phase, significant differences were observed only for ipsilateral measurements obtained with the VP1T probe. Normalization effectively reduced variability, and significant differences during reperfusion were detected with both probes. Conclusions: Although the multi-fiber probe consistently recorded higher perfusion values, normalization was essential to reduce variability and to enhance the detection of microvascular reactivity parameters. Full article

Background and Objectives: This meta-analysis aimed to compare the clinical efficacy and safety of the Thulium fiber laser (TFL) and Holmium:Yttrium-Aluminum-Garnet (Ho:YAG) laser for ureteroscopic lithotripsy, considering the distinct technical characteristics of these two systems. Materials and Methods: Following the PRISMA guidelines and PROSPERO registration (CRD42023461573), a systematic search of PubMed, EMBASE, Cochrane Library, and Web of Science was conducted through August 2025. We included randomized controlled trials and non-randomized comparative studies comparing TFL and Ho:YAG laser in patients undergoing ureteroscopic management for urolithiasis. The primary outcomes were the stone-free rate (SFR) and complication rates (intraoperative and postoperative). Results: Thirteen studies involving 2217 patients were included. Overall, the TFL group demonstrated a significantly higher SFR compared to the Ho:YAG group (OR = 1.57, 95% CI 1.20–2.06, p = 0.001). In subgroup analysis, TFL showed superior SFR compared to Ho:YAG without pulse modulation (OR = 1.69, p = 0.01) and comparable efficacy to Ho:YAG with pulse modulation (OR = 1.52, p = 0.24). Regarding safety, no significant difference was observed in the intraoperative complication rate (OR = 0.77, 95% CI 0.35–1.70, p = 0.52) or the postoperative complication rate (OR = 1.02, 95% CI 0.65–1.60, p = 0.93) between the two groups. Conclusions: TFL provides a superior SFR compared to the Ho:YAG laser overall, a benefit primarily driven by its significant outperformance of standard Ho:YAG systems without pulse modulation. Importantly, TFL demonstrates comparable efficacy to modern Ho:YAG systems equipped with pulse modulation. The safety profile of TFL, including intraoperative and postoperative complications, is comparable to that of the Ho:YAG laser. Our findings suggest that TFL is a highly effective and safe modality for ureteroscopic lithotripsy, offering distinct advantages over standard Ho:YAG lasers while performing comparably to the latest pulse-modulated systems. Full article

We report on sub-50 fs pulse generation from a diode-pumped mode-locked laser based on an ytterbium-doped monoclinic potassium yttrium double tungstate crystal operating in the 1 μm spectral region. Pumping by a low-power, spatially single-mode, fiber-coupled laser diode at 976 nm, a maximum continuous-wave output power of 433 mW at 1066.1 nm was obtained. Using a quartz-based intracavity Lyot filter, an exceptionally broad continuous-wavelength tuning range of 98 nm was achieved. In the mode-locked regime, the diode-pumped Yb:KY(WO₄)₂ laser delivered soliton pulses as short as 46 fs at a central wavelength of 1069.2 nm by employing a SEmiconductor Saturable Absorber Mirror. To the best of our knowledge, these results represent the broadest continuous-wave tuning range and the shortest pulse duration ever reported for lasers based on ytterbium-doped monoclinic double tungstate crystals. Full article

The shift toward lightweight powertrain architectures necessitates a detailed characterization of polymer gears to verify their efficiency and durability. This study investigated the effectiveness of non-contact structured-light 3D scanning for evaluating the surface topography and dimensional tolerance quality of polymer gears produced via distinct manufacturing technologies. A structured-light 3D scanner was used to capture dense point clouds (exceeding 6 million points) of gears produced by three methods: conventional hobbing (POM-C), Material Extrusion (MEX) with carbon fiber reinforcement, and Selective Laser Sintering (SLS). The manufactured parts were compared against the nominal Computer Aided Design (CAD) models to evaluate their geometrical deviations in accordance with DIN 3961 and surface roughness parameters per ISO 25178. The experimental results revealed a consistent ranking of manufacturing quality. The conventionally hobbed POM-C gear exhibited superior precision, achieving DIN quality grades of Q9–Q10 and the smoothest surface finish (S_a = 5.0 µm). Among additive manufacturing techniques, SLS-printed PA 12 showed intermediate quality (Q11, S_a = 12 µm), whereas MEX-printed PPS-CF exhibited significant deviations (exceeding Q12) and the highest surface irregularity (S_a = 25 µm) due to stair-stepping effects. These findings indicate that while additive manufacturing offers geometric flexibility, conventional hobbing retains a decisive advantage in dimensional precision. The optical scanning methodology demonstrated here constitutes an efficient metrological framework for gear quality control, with potential applications extending to the quality assurance of additively manufactured adaptive fixtures and assembly tooling, including automotive assembly operations. Full article

This study addresses the problem of whispering gallery mode (WGM) selection in spherical microresonators by means of their femtosecond micro-processing. The proposed method involves fabrication on the microsphere surface of defects playing the role of scattering elements for higher-order modes with low azimuthal mode indices. These two T-shaped trenches are created using femtosecond laser ablation, with a depth of 2 microns, gap of 30 microns between them, and each of length of 20 microns along the equatorial direction. A tapered fiber with a sub-micron waist diameter serves as the excitation element for WGMs. This method allows for spectral purification of the WGMs, reducing the number of resonances by 180 times, with a quality factor of $Q>{10}^5$ for the non-inverted spectrum in the form of resonance dips. Additionally, an inverted spectrum with narrow resonance peaks of about 35%, low background level and single mode regime with 3 dB side peak suppression has been simultaneously achieved in the taper transmission, for the first time to our knowledge. The latter was obtained by exciting the microsphere at the taper waist. These results hold promise for the development of narrowband filters, laser mode selectors, and optical sensors based on microresonators. Full article

In the current paper, the nonlinear absorption characteristics and laser modulation performance of the ternary anisotropic semiconductor material ZrGeTe₄ were successfully explored. The recovery time of the ZrGeTe₄-PVA thin film was measured to be 5.74 ps by the pump–probe technology. By employing ZrGeTe₄ as a saturable absorber, a passive mode-locked Yb-doped fiber laser was demonstrated for the first time. In the 1 µm mode-locked operation, the central wavelength was 1031.29 nm, the pulse repetition rate was 24.85 MHz, and the pulse width was 786.3 ps. In an Er-doped fiber laser operating at a wavelength of 1561.10 nm, the pulse width was as short as 1.26 ps with a repetition rate of 4.38 MHz. The results show that ZrGeTe₄ has excellent broadband nonlinear optical characteristics. Full article