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Fractional dynamics of an erbium-doped fiber laser model
摘要： In this paper we investigate the model of the time-fractional dynamics of an erbium-doped fiber laser model (TFDEFL) with Liouville–Caputo (LC), Caputo–Fabrizio–Caputo (CFC) and Atangana–Baleanu–Caputo (ABC) time-fractional derivatives. We employ the homotopy analysis transform method (HATM) to calculate approximate solutions for the TFDEFL model. This method gives the solution in the form of a rapidly convergent series that can ensure the convergence in solving the resultant series. We study the convergence analysis of HATM by computing the interval of convergence through the h-curves, the residual error function and the average residual error, respectively. We also show the effectiveness and accuracy of this method by comparing the approximate solutions based upon the LC, CFC and ABC time-fractional derivatives.
关键词： Erbium-doped fiber laser model,Fractional calculus,Fractional derivatives,Analytical solutions,Homotopy analysis transform method
更新于2025-09-11 14:15:04
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[IEEE 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Munich, Germany (2019.6.23-2019.6.27)] 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Intra-Cavity Mode-Selective Coupler Assisted Ultrafast Cylindrical Vector Fiber Laser
摘要： Cylindrical vector beam (CVB) fiber lasers have attracted great attentions due to their promising applications in optical communications, super-resolution imaging and optical trapping. Recently, it has been proved that mode-selective coupler (MSC) is an efficient method for generating CVBs in all-fiber lasers [1-3]. However, to date, the reported MSC-assisted CVB lasers have a common feature that the fundamental transverse mode (LP01) oscillates in the laser cavity whereas the high-order modes are outside the laser cavity. To some extent, such cylindrical vector lasers belong to the external mode conversion, rather than the direct generation of high-order modes inside the laser cavity. In this contribution, we present an intra-cavity MSC assisted CVB fiber laser in a compact linear-cavity mode-locked by using a semiconductor saturable absorber mirror (SESAM). The laser architecture is shown in Fig. 1(a), which consists of a 5 m Er-doped fiber, a 980/1550 wavelength-division multiplexer (WDM) pumped by a 980 nm laser, a polarization controller (PC), a 90% high coupling ratio MSC with an insertion loss of 0.3 dB. A fiber end-facet mirror is sandwiched between the two fiber ferrules and a SESAM mode locker has a modulation depth of 18%. The rest of cavity consists of ~14.3 m standard single-mode fiber (SMF) and ~0.6 m few mode fiber (FMF). Self-started mode-locking occurs when the pump power reaches ~35 mW. Thanks to the high coupling efficiency of intra-cavity mode converter, LP01 mode in the SMF is sufficiently coupled to LP11 mode in the FMF when it passes through the MSC. The reflected LP11 mode from the mirror can be partially coupled back to the SMF with a low loss, resulting in the laser oscillation. In this case, the laser operates between MSC and the mirror in the LP11 mode, which outputs from the FMF, meanwhile the LP01 mode oscillates in the remaining section of the linear-cavity. Eventually, the laser can allow the direct generation of LP11 mode from the laser cavity. Typical laser output characteristics such as broadband spectra, pulse train and output power are shown in Fig. 1(b)-(e). The laser operates at the wavelength of 1562 nm with a 3-dB bandwidth of ~4.4 nm and a repetition rate of 5.2 MHz. Radially polarized and azimuthally polarized ultrafast CVBs are obtained by adjusting the PC, and corresponding donut beam profiles are demonstrated by checking the rotating intensity distribution through the linear polarizer, as presented in Fig. 1(f).
关键词： Cylindrical vector beam,mode-selective coupler,ultrafast,fiber laser
更新于2025-09-11 14:15:04
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Ytterbium-doped fiber laser as pulsed source of narrowband amplified spontaneous emission
摘要： We report random noise pulsed regime of an ytterbium-doped fiber laser arranged in common Fabry-Perot configuration. We show that the laser output obeys the photon statistics inherent to narrowband amplified spontaneous emission and that the noise pulsing is properly addressed in terms of probability density and autocorrelation functions. Our novel approach reveals, in particular, that the regime’s coherence time dramatically shortens, from few ns to tens ps, with increasing laser power.
关键词： narrowband amplified spontaneous emission,coherence time,photon statistics,probability density,ytterbium-doped fiber laser,autocorrelation functions,random noise pulsed regime
更新于2025-09-11 14:15:04
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Novel thulium fiber laser for endoscopic enucleation of the prostate: A prospective comparison with conventional transurethral resection of the prostate
摘要： Objective: To compare the efficacy and safety of a novel thulium fiber laser for endoscopic enucleation of the prostate with monopolar transurethral resection of the prostate in patients with smaller glands (<80 cc). Methods: A total of 51 patients underwent thulium fiber laser enucleation of the prostate, and 52 patients underwent monopolar transurethral resection of the prostate. All patients were assessed preoperatively, and at 3, 6, and 12 months postoperatively (International Prostate Symptom Score, maximum urine flow rate, International Prostate Symptom Score-quality of life). Preoperative prostate volumes and prostate-specific antigen levels were complications were graded according to the Clavien classification. Results: Mean surgery time was longer in the thulium fiber laser enucleation of the prostate group (46.6 ± 10.2 vs 39.9 ± 8.6 min, P < 0.001), while catheterization and hospital stay were greater (P < 0.001). At 12 months, there were no differences in functional outcomes (International Prostate Symptom Score, maximum urine flow rate). Despite comparable prostate volumes at 12 months (P = 0.864), the prostate-specific antigen level in the thulium fiber laser enucleation of the prostate group (0.5 ± 0.5 ng/mL) was lower than in the transurethral resection of the prostate group (1.1 ± 1.0 ng/mL; P < 0.001). Hemoglobin and serum sodium decrease was lower in the thulium fiber laser enucleation of the prostate group (1.01 ± 0.4 g/dL and 1.1 ± 1.1 mmol/L) than in the transurethral resection of the prostate group (1.8 ± 0.8 g/dL and 4.1 ± 1.1 mmol/L; P < 0.001). Urinary incontinence rates at 12 months were comparable (P = 0.316). Conclusions: Thulium fiber laser enucleation of the prostate with novel thulium fiber laser in patients with smaller prostate glands (<80 cc) is comparable to transurethral resection of the prostate in voiding parameters improvement and complication rates. At the same time, the technique allows for a more substantial prostate-specific antigen decrease, indicating more complete removal of adenoma.
关键词： transurethral resection of the prostate,benign prostatic hyperplasia,endoscopic enucleation of the prostate,thulium fiber laser
更新于2025-09-11 14:15:04
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Monte Carlo simulation of a transversely excited solar-pumped fiber laser
摘要： A Monte Carlo ray-tracing simulation was developed for a transversely excited solar-pumped fiber laser without focusing optics. To make this possible, the fiber is immersed in a liquid sensitizer and sandwiched between highly reflective mirrors. The top reflector is dichroic to transmit solar radiation but reflect fluorescence to confine photons that match the absorption band of the active fiber. Simulation was used to evaluate the validity of the concept and optimize device performance. For comparison with the calculations, preliminary experiments were conducted by illuminating a 30 cm aperture, laser module with a solar simulator. The observed gains were in good agreement with the calculations for various conditions, such as sensitizer concentration and mirror reflectivity. Finally, we show that the predicted output power reaches 29 mW when the fiber length is optimized, and it will be enhanced to 150 mW with 0.21% solar-to-laser efficiency under the assumption of a reabsorption-free sensitizer.
关键词： unconcentrated,dichroic mirror,Monte Carlo simulation,sensitizer,solar-pumped fiber laser,transversely excited
更新于2025-09-11 14:15:04
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Mechanical and tribological performance of fiber laser cladded h-BN + SS316 composite on SS316 surface
摘要： Laser cladding is a unique process for adding one material to the surface of another base material by utilizing high energy and coherent laser beam. For the present investigation, h-BN (hexagonal boron nitride) + SS316 composite coating was applied on SS316 substrate surface by fiber laser cladding operations. Under the influence of various input process parameters, the surface morphology, microstructure, X-ray diffraction, clad layer thickness, micro-hardness, and tribological behaviour of the composite coating were examined. The result showed good metallurgical bonding between the clad powder and substrate surface. Surface morphology did not show any pores and cracks on the clad surface. From FESEM analysis, the clad surface was found to be smooth and free from any crack propagation during laser processing. X-ray diffraction analysis showed formation of Fe3N, Cr2N, CrB, B2C5N2, γ- (Ni, Fe), h-BN phases which are responsible for enhancing mechanical and tribological properties of the clad layer. During the study, the micro-hardness of the clad layer was found to increase with an increase in % v/v of h-BN by 2-2.5 times compared (525 HV0.3) to parent material (220 HV0.3). Further, dry sliding wear test was carried out with Pin-On-Disc, showed that the coefficient of friction value decreased significantly from 0.560 (parent surface) to 0.251 (clad surface).
关键词： solid lubricant,micro-hardness,fiber laser cladding,coefficient of friction,h-BN,microstructure
更新于2025-09-11 14:15:04
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Bright/dark switchable mode-locked fiber laser based on black phosphorus
摘要： Stable bright/dark switchable mode-locked nanosecond pulse fiber laser incorporating black phosphorus (BP) was demonstrated in the Yb-doped fiber ring cavity for the first time, to the best of our knowledge. The high-quality BP saturable absorber (SA) was fabricated by the modified electrochemical delamination exfoliation process. The states between bright and dark pulse could be switched by simply adjusting the intra-cavity polarization states, and close agreement with the cubic Ginzburg-Landau equation (CGLE) models is present.
关键词： Mode-locked,Bright/dark pulse,Fiber laser,Black phosphorus
更新于2025-09-11 14:15:04
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Nanostructure fabrication on the top of laser-made micropillars for enhancement of water repellence of aluminium alloy
摘要： Fabrication of superhydrophobic surfaces is a popular topic in research and industry due to many potential applications including self-cleaning, anti-icing or drag reduction. Laser micro and nanostructuring is an efficient method to replicate lotus leaves double-scale structures to achieve superhydrophobicity without chemical treatment. Immediately after laser processing, samples are hydrophilic and become hydrophobic in a few days, exposed to atmospheric conditions. This time was significantly reduced by vacuum processing to only 4 h. Two-step fabrication method of superhydrophobic surfaces have been developed using nanosecond laser system. In the first step, large scale micropillars are fabricated and covered by nano-scale protrusions in the following step using defocused laser beam. The nanostructure formation increased the apparent contact angle from 149° to 175°.
关键词： Nanostructures,Aluminium,Superhydrophobic,Fiber laser
更新于2025-09-11 14:15:04
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Dynamic interaction between a laser beam and keyhole front wall during fiber laser welding
摘要： A bright spot (laser beam spot-center-induced metal vapor) on the keyhole front wall (KFW) was observed during fiber laser keyhole welding of a ‘sandwich’ specimen to reveal the interaction between the laser beam and the KFW. The dynamic behavior of the bright spot shows that the keyhole formation is the result of periodical drilling of the laser beam spot center on the KFW during welding. Welding parameters have little effect on the drilling period. The drilling speed first increases and then decreases with the increase in the keyhole depth, and the next drilling process begins before the drilling speed reduces to 0 m s?1. The average drilling speed can be increased by increasing the line energy or power density of the laser.
关键词： keyhole front wall (KFW),drilling speed,interaction,fiber laser welding,period
更新于2025-09-11 14:15:04
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Nonlinear optical properties of tungsten disulfide as saturable absorber based on Q-switched fiber laser
摘要： In this paper, nonlinear optical properties of tungsten disulfide are studied. Tungsten disulfide (WS2) is prepared as saturable absorber (SA) with the microstructured optical fiber. When the SA based on WS2 is assembled into a fiber laser, Q-switched operation is demonstrated. The 2 nm spectral width is obtained at the central wavelength of 1531 nm. The signal-to-noise ratio is about 80 dB, which indicates that the fiber laser is very stable. The shortest pulse duration is 800 nm at the maximum input power of 650 mW. The conclusion shows that WS2 is a good nonlinear optical material.
关键词： Saturable absorber,Fiber laser,Tungsten disulfide,Nonlinear optical properties
更新于2025-09-11 14:15:04