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Third and fifth harmonics generation in air and nanoparticle-containing plasmas using 150-kHz fiber laser
摘要： High-pulse repetition rate lasers allow significant enhancement in the average power of the low-order harmonics generation in isotropic media. We report on the third (343-nm) and fifth (206-nm) harmonics generating in air and different nanoparticle-containing laser-produced plasmas by applying Yb-doped fiber laser delivering 37-fs, 100-kHz, 1030-nm, 0.5-mJ pulses. Different characteristics of these processes (power and density dependences, influence of impeding processes, role of synthesized nanoparticles, variations of the spectral modulation of driving pulses, etc.) are analyzed. We compare the formation of the plasmas on the surfaces of aluminum, carbon, manganese, and titanium bulk species, as well as quantum dots of metal sulfides as the media for low-order harmonics generation, using 250-fs (1030-nm) and 5-ns (1064-nm) heating pulses at different delays between the heating and driving pulses. Average power of about 20 mW was estimated for the third harmonic emission from metal plasmas, with 3 × 1016 UV photons (343 nm) emitted per second.
关键词： Third harmonic generation,Fifth harmonic generation,Nanoparticle-containing plasmas,High-pulse repetition rate,Fiber laser
更新于2025-09-23 15:19:57
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Effect of fiber laser welding on solute segregation and proprieties of CoCrCuFeNi high entropy alloy
摘要： The effect of fiber laser welding on solute segregation and proprieties of CoCrCuFeNi high entropy alloy was investigated. The microstructure and mechanical properties of the parent metal and the fusion zone were comparably studied. The parent metal was dendrite, with elemental Cu segregated to interdendrites owing to small bonding energies with Fe, Co, Ni, and Cr atoms. After laser welding, the microstructure in the center of the fusion zone was predominantly equiaxial grains, whereas that in the edge region was mainly columnar crystals oriented perpendicular to the fusion line. The segregation of Cu in the fusion zone is alleviated by grain refinement and molten pool agitation. Because of the fine-grain strengthening and precipitation hardening effect, the hardness and yield stress of the fusion zone are 12.84% and 26.87% greater than those of the parent metal, respectively.
关键词： CoCrCuFeNi,mechanical properties,fiber laser welding,solute segregation
更新于2025-09-23 15:19:57
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A simple FBG Fabry-Perot sensor system with high sensitivity based on fiber laser beat frequency and Vernier effect
摘要： We numerically study the dynamics of supercontinuum generation (SCG) for a variety of possible combinations of photonic crystal fibers (PCFs) and ultrafast fiber laser pulses that the current technologies offer. Three types of PCFs typically used in SCG and four representative types of ultrafast fiber laser pulses are considered for this combinatorial study. We numerically model and qualitatively discuss the nonlinear evolution of the pulses for their whole 12 combinatorial cases. We also quantitatively analyze their output spectra and organize a performance chart for them in terms of spectral bandwidth, flatness, and degree of spectral coherence. Finally, we suggest the most viable combinations among the given PCFs and ultrafast fiber laser pulses in order for generating a target supercontinuum spectrum for various specific cases.
关键词： Optical fiber laser,supercontinuum generation,nonlinear optics,ultrashort pulse
更新于2025-09-23 15:19:57
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Characteristic Test Analysis of Graphene Plus Optical Microfiber Coupler Combined Device and Its Application in Fiber Lasers
摘要： In this study, a graphene and optical microfiber coupler (OMC) integrated device (GOMC) was proposed and fabricated. After its characteristic analysis and testing, it was applied to the development of adjustable multi-wavelength fiber lasers. By integrating the OMC with graphene, the polarization dependence of OMC was enhanced. Meanwhile, the novel GOMC was given the capabilities of filtering, coupling, beam splitting, and polarization correlation. When the GOMC was integrated as a filter and beam splitter into the ring cavity of the fiber laser, the proposed GOMC-based fiber laser could achieve single-wavelength and multi-wavelength regulated output. The laser had a 3 dB linewidth of less than 30 pm, a signal-to-noise ratio of approximately 40 dB, and an output power fluctuation of less than 1 dB. The GOMC could also be used for the development of functional devices, such as adjustable mode lockers and mode coupling selectors, which provide an excellent experimental platform for new fiber lasers and the research of multi-dimensional light-field manipulation.
关键词： filter,optical microfiber coupler,graphene,fiber laser
更新于2025-09-23 15:19:57
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High-power, cascaded random Raman fiber laser with near complete conversion over wide wavelength and power tuning
摘要： Cascaded Raman fiber lasers based on random distributed feedback (RDFB) are proven to be wavelength agile, enabling high powers outside rare-earth doped emission windows. In these systems, by simply adjusting the input pump power and wavelength, high-power lasers can be achieved at any wavelength within the transmission window of optical fibers. However, there are two primary limitations associated with these systems, which in turn limits further power scaling and applicability. Firstly, the degree of wavelength conversion or spectral purity (percentage of output power in the desired wavelength band) that can be achieved is limited. This is attributed to intensity noise transfer of input pump source to Raman Stokes orders, which causes incomplete power transfer reducing the spectral purity. Secondly, the output power range over which the high degree of wavelength conversion is maintained is limited. This is due to unwanted Raman conversion to the next Stokes order with increasing power. Here, we demonstrate a high-power, cascaded Raman fiber laser with near complete wavelength conversion over a wide wavelength and power range. We achieve this by culmination of two recent developments in this field. We utilize our recently proposed filtered feedback mechanism to terminate Raman conversion at arbitrary wavelengths, and we use the recently demonstrated technique (by J Dong and associates) of low-intensity noise pump sources (Fiber ASE sources) to achieve high-purity Raman conversion. Pump-limited output powers >34W and wavelength conversions >97% (highest till date) were achieved over a broad – 1.1μm to 1.5μm tuning range. In addition, high spectral purity (>90%) was maintained over a broad output power range (>15%), indicating the robustness of this laser against input power variations.
关键词： wavelength conversion,spectral purity,random distributed feedback,Raman fiber laser,high-power
更新于2025-09-23 15:19:57
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Environmentally stable black phosphorus saturable absorber for ultrafast laser
摘要： Black phosphorus (BP) attracts huge interest in photonic and optoelectronic applications ranging from passive switch for ultrafast lasers to photodetectors. However, the instability of chemically unfunctionalized BP in ambient environment due to oxygen and moisture remains a critical barrier to its potential applications. Here, the parylene-C layer was used to protect inkjet-printed BP- saturable absorbers (BP-SA), and the efficacy of this passivation layer was demonstrated on the stable and continuous operation of inkjet-printed BP-SA in harsh environmental conditions. BP-SA was integrated in an erbium-doped ring laser cavity and immersed in water at ~60°C during operation for investigation. Mode-locked pulses at ~1567.3 nm with ~538 fs pulse width remained stable for >200 h. The standard deviation of spectral width, central wavelength, and pulse width were 0.0248 nm, 0.0387 nm, and 2.3 fs, respectively, in this period, underscoring the extreme stability of BP-SA against high temperature and humidity. This approach could enable the exploitation of BP-based devices for photonic applications when operating under adverse environmental conditions.
关键词： black phosphorus,fiber laser,2D materials
更新于2025-09-23 15:19:57
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Atomic layer deposition of zirconium oxide thin film on an optical fiber for cladding light strippers
摘要： Cladding light strippers are essential components in high-power fiber lasers used for removal of unwanted cladding light that can distort the beam quality or even damage the whole fiber laser system. In this study, an Atomic Layer Deposition system was used for the first time to prepare the cladding light stripper devices using a 40 nm thick zirconia layer grown on optical fiber. The thickness of the zirconia coating was confirmed using the Scanning Electron Microscopy (SEM) and the Ellipsometry techniques. The elemental analysis was also performed using the wavelength dispersive X-ray spectroscopy technique. The Raman spectroscopy and XRD data confirm the structure of the atomic layer deposition-grown zirconia thin films to be predominantly amorphous. The cladding light stripper devices formed using the zirconia thin films with the lengths of 8.5 and 15.5 cm were able to strip approximately 30% (~1.5 dB) and 40% (~2.3 dB) of the unwanted cladding light.
关键词： zirconium oxide,atomic layer deposition,cladding light stripper,thin film,Fiber laser
更新于2025-09-23 15:19:57
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Wavelength-switchable erbium-doped fiber laser incorporating fiber Bragg grating array fabricated by infrared femtosecond laser inscription
摘要： Wavelength-switchable fiber laser systems have many potential applications. Herein, the use of an erbium-doped fiber laser based on parallel fiber Bragg gratings (FBGs) (ASE: amplified spontaneous emission; BRM: broadband reflection mirror; CCD: charged-coupled device; EDFL: erbium-doped fiber laser; FBG: fiber Bragg gratings; IR: infrared; MZI: Mach–Zehnder interferometer; OSA: optical spectrum analyzer; OC: output coupler; PC: polarization controller; SNR: signal-to-noise ratios; 3D: three-dimensional; wavelength division multiplexing (WDM)) is proposed to achieve C + L band triple-wavelength-switchable laser output at approximately 1.5 μm. In the proposed system configuration, three parallel FBGs with different resonant wavelengths were fabricated using an 800 nm femtosecond pulsed laser. The proposed fiber laser incorporates first-order FBGs with the periods of 538, 542, and 547 nm. The femtosecond laser was propagated through polyimide coating and cladding and was focused onto the fiber core by a 63× oil lens, while FBGs were inscribed with the use of a point-by-point method to generate resonant wavelengths at 1555.3, 1569.2, and 1583.1 nm. When the FBGs were used as wavelength selectors, a lasing threshold of 85 mW was obtained, and switchable lasing with stable single- and dual-wavelength outputs was achieved based on the adjustment of a polarization controller. Concerning the switchable single-wavelength lasing, the signal-to-noise ratio was greater than 37.23 dB, and the 3 dB linewidth was less than 0.09 nm. The respective power fluctuation measurements were less than 0.22 and 0.68 dB for the single- and dual-wavelength lasers at 26 °C over a scan time of 30 min.
关键词： Erbium-doped fiber laser,Femtosecond laser,Point-by-point wavelength generation method,Fiber Bragg grating
更新于2025-09-19 17:13:59
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Comparison of fractional neodymium-doped yttrium aluminum garnet (Nd:YAG) 1064-nm picosecond laser and fractional 1550-nm erbium fiber laser in facial acne scar treatment
摘要： To compare the safety and efficacy of fractional neodymium-doped yttrium aluminum garnet (Nd:YAG) 1064-nm picosecond laser and fractional 1550-nm erbium fiber laser in acne scar treatment and to assess the adverse effects and complications of the two devices. Thirty patients with cosmetically similar acne scars on both sides of the faces were enrolled and treated four times at 4-week intervals. Each side of the face was treated with either fractional 1064-nm Nd:YAG picosecond laser or fractional 1550-nm erbium fiber laser. Efficacy was evaluated using digital photography taken at baseline and 5 months by a blinded dermatologist using the ECCA grading scale (échelle d’évaluation clinique des cicatrices d’acné). Patient overall satisfaction and self-rated improvement scores were recorded at baseline and 5 months. Adverse effects were recorded at every visit. Twenty-seven patients completed the study. Both devices demonstrated significant median ECCA score improvement from baseline (P < 0.001). However, there was no significant difference between the two in terms of median ECCA score improvement, patients’ perception of scar improvement, and overall satisfaction. Considering the adverse effects, more pinpoint bleeding was significantly observed with the picosecond laser (P = 0.002), whereas more pain was noted with the erbium laser (P < 0.001). Both fractional 1064-nm Nd:YAG picosecond laser and fractional 1550-nm erbium fiber laser are safe and effective in the treatment of acne scars. Costs should be taken into consideration when deciding on which device to use to maximize treatment outcomes.
关键词： Erbium fiber laser,Acne scar,Picosecond laser,Acne scar treatment,Fractional laser
更新于2025-09-19 17:13:59
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An experimental study of geometrical characteristic in low power fiber laser drilling of Monel k-500 superalloy
摘要： Precise holes in advanced dif?cult to cut nickel-based superalloys can be drilled with ease by the method of ?ber laser drilling. Laser trepanned drilling has become more acceptable laser percussion drilling as it can produce better hole quality and generate macro or micro size hole. On the basis of geometrical quality feature like hole taper for drilling small diameter hole in dif?cult to cut Monel k-500 superalloy sheet laser trepanned drilling process performance studies have been made in the present research paper. The laser drilling has become a highly non-linear and complex process as there is involvement of different and large process parameters. Application of response surface methodology (RSM) has been made for attaining optimization by way of handling the non-linearity and complexity. Input process parameters like sawing angle, power setting, duty cycle, pulse frequency and trepanning speed have been used in this study. A well-designed experimental matrix has supplied essential data to ?nd out the in?uence of signi?cant process parameters on characteristic of the hole taper. Development of reliable empirical models has been achieved to relate different quality characteristic.
关键词： Hole taper,RSM,Laser trepan drilling,Monel k-500,Fiber laser
更新于2025-09-19 17:13:59