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Influence of the degree of dilution with laser beam vacuum-welded Cu-Al mixed joints on the electrical properties
摘要： A great potential for light-weight construction lies in the substitution of copper by aluminum. The state of the art, so far, has put the focus only on the identification of the crack-sensitive intermetallic phase. External influential factors, such as temperature, current-feed and time bring about the change of the joining zone structure by diffusion and electro-migration. Moreover, a temporal change of the technological properties (increase of the electric resistance, reduction of strength) of the dissimilar material joint will occur. Findings about this behavior for laser beam under vacuum welds will allow to draw conclusions about the expected life-time.
关键词： Laser beam welding,Dissimilar material joint,Single-moder fiber laser,Copper,Aluminum
更新于2025-09-12 10:27:22
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Parameter development and characterization of laser metal deposited Ti alloy powders for use at elevated temperatures
摘要： Powder-based laser metal deposition (LMD) of Ti alloys enables the manufacturing of geometrical complex structures with tailored properties for high-temperature applications. The most important parameters for the LMD-process are the laser power, process velocity, laser focus position, gas flow and powder feed rate. Compared to the predominantly used Ti-6Al-4V, Ti-6Al-2Sn-4Zr-2Mo shows a higher oxidation resistance and a lower creep rate. For determining suitable process conditions, a parameter study using Ti-6Al-2Sn-4Zr-2Mo powder is performed. Subsequent, the parameter transfer to a γ-TiAl alloy is examined. The assessment of the dissimilar-LMD-structures is conducted by visual inspection, radiography inspection, microstructural analysis and hardness measurements.
关键词： fiber laser,γ-TiAl,laser metal deposition,microstructure characterization,Ti alloy
更新于2025-09-12 10:27:22
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Efficacy and safety of 1927 nm fractional Thulium fiber laser for the treatment of melasma: a retrospective study of 100 patients
摘要： Background: Melasma is an acquired hyperpigmentation of the skin that mostly affects areas exposed to the sun. The treatment of melasma can be challenging as it is prone to relapse. Recently, new laser and light-based treatment options have been used; one of these treatment modalities is the 1927 nm fractional Thulium fiber laser. Objective: This study aimed to retrospectively evaluate the efficacy and safety of a 1927 nm fractional Thulium fiber laser for the treatment of melasma. Materials and methods: This study retrospectively evaluated patients who were admitted to the dermatology outpatient clinic between September 2015 and March 2018 and treated with a 1927 nm fractional Thulium fiber laser. The MASI score was used to assess improvements of the lesions. Results: The current study included a total of 100 patients who received 1927 nm fractional Thulium fiber laser treatment. Each patient received two treatments at one month intervals. The mean baseline MASI score was 11.8 ± 6.3, the mean MASI score after the first session was 6.7 ± 4.1, and the mean MASI score after the second session was 3.4 ± 3.8. The differences between these three MASI scores were significant, and the laser treatment had no major side effects. Conclusion: Results of this study indicate that the 1927 nm fractional Thulium fiber laser is a safe and effective treatment option for melasma.
关键词： Melasma,1927 nm thulium fiber laser,fractional laser
更新于2025-09-12 10:27:22
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Research of technological possibility of increasing erosion resistance rotor blade using laser cladding
摘要： The publication describes the results of the research of the influence of the parameters of the mode of a laser deposition on the metallurgy of deposited layers, mechanical characteristics and deformations of the samples. Plates, which had made of PC E36 steel and 15Cr11MoW steel, were used as samples. According to the results of experimental researches the peripheral areas of the input edges of the blades were made. Also, an experimental research was conducted on how the parameters of the mode and trajectory of the deposition influence on mechanical and operational characteristics, as well as the deformations forming in the product during the laser surfacing of the Stellite 6 alloy influence on the heat-resistant high-alloy steel 15Cr11MoW.
关键词： Rotor blade,15Cr11MoW,Stellite 6,ytterbium fiber laser,cladding blade,РС Е36,Inconel 625,laser cladding
更新于2025-09-12 10:27:22
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Oxidation-resistance Black Phosphorus Enable Highly Ambient-stable Ultrafast Pulse Generation at 2 μm Tm/Ho-doped Fiber Laser
摘要： Black phosphorus (BP) ranks among the most promising saturable absorber materials for ultrafast pulse generations at 2 μm. However, the easy-to-degrade characteristic of BP seriously limits the long-term operation of ultrafast fiber lasers and hence becomes a bottleneck for its relevant practical applications. In this paper, a modified electrochemical delamination exfoliation process was explored to produce high-performance, large-size and oxidation-resistance BP nanosheets, where BP nanosheets in high yield with evenly coated tetra-n-butyl-ammonium (TBA) organics by precisely controlling the intercalation chemistry can be obtained. A mode-locked Tm/Ho co-doped fiber laser with high temporal stability and long-term operation capability was demonstrated based on the innovatively-fabricated BP saturable absorber. The self-starting mode-locking operation featuring high signal-to-noise ratio of 58 dB and long-term stability has been verified for at least three weeks, which indicates the successful passivation of the employed synthesis method. These results fully indicated that passivated BP is an efficient candidate in 2 μm range ultrafast photonics field, which will promote the ultrafast optical application of BP and also other infrared photonic and photoelectronic devices.
关键词： mode-locked laser,2D materials,fiber laser,mid-infrared,black phosphorus
更新于2025-09-12 10:27:22
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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) - Widely Tunable Tm:CaF <sub/>2</sub> Laser In-Band Pumped by a Fiber Laser at 1610 nm
摘要： High-brightness and tunable lasers operating in the 1800-2000 nm wavelength region are very attractive for applications such as spectroscopy, atmospheric remote sensing and medical surgery. So far, Tm3+-doped crystalline hosts, such as YLF and YAG, have proven to be ones of the most interesting gain materials [1, 2]. Among other available hosts, Tm:CaF2 offers a high thermal conductivity and a very broad emission bands due to multisite crystal structure. Therefore, Tm:CaF2 is a good candidate for high-power and broadband tunable laser emission between 1750 nm and 2000 nm. However, there are only a few reports on Tm:CaF2 laser operation, mainly because of the lack of powerful pump sources at the optimum absorption wavelength of 767 nm, when using cross-relaxation process [3]. In comparison, in-band pumping of Tm-doped materials can be very efficient as the quantum defect may approach 85% [4, 5]. In this contribution, we demonstrate the tunable laser emission of Tm:CaF2 crystal at 1775-1955 nm using in-band pumping by a fiber laser system at 1610 nm. We employed a linear plane-concave resonator built around a Tm:CaF2 crystal doped at 3% and 5 mm long (Fig. 1). The plane input mirror (M1) has transmission of 98% at the pump wavelength and is HR near 1850 nm, the concave output mirror (M2) has a transmission of 5-10% at 1850 nm. A birefringent plate can be inserted into the cavity at Brewster angle to act as a wavelength selective component. The pump source used in the experiments is an all-fiber MOPA specifically designed for an emission wavelength at 1610 nm. The MOPA consists of a 12 mW seed laser diode amplified into a two-stage fiber amplifier. A 50 nm band-pass filter centered at 1620 nm was used to suppress the ASE at 1530-1560 nm from the pre-amplifier stage. The power-amplifier stage is based on a 10 m long Er/Yb-codoped double-clad fiber pumped at 915 nm in order to maximize the gain on the long wavelength side. The 1610 nm MOPA laser source achieves more than 2.5 W of diffraction-limited power incident on the crystal, with a 0.5 nm spectral linewidth. Using a 10% transmission output coupler and without the birefringent plate, a maximum output power of 1.25 W is obtained, which represents a conversion efficiency of 70% with respect to the absorbed pump power. Inside the resonator, the pump beam waist is measured to be 45 μm and the signal beam waist is about 60 μm. As shown in Fig. 2, using an intra-cavity birefringent plate and a T2=5% output coupler, it was possible to tune the laser over 180 nm. Compared to a previous report [3], shorter wavelengths below 1800 nm are achieved thanks to the high-brightness pump source at 1610 nm. At the highest output power, the laser beam quality factors M2 of the laser is measured to be 1.1. These results are promising for the future development of in-band pumped mode-locked Tm:CaF2 laser.
关键词： fiber laser,Tm:CaF2,tunable laser,in-band pumping,1610 nm
更新于2025-09-12 10:27:22
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Elemental micro-segregation characteristic of fiber laser welded Hastelloy C-276 sheet
摘要： The elemental micro-segregation characteristic within the weld zone for ytterbium fiber laser welded Hastelloy C-276 sheet was investigated. The analysis of segregation ratio and equilibrium distribution coefficient of elements, determined through EDS data, indicate the reduction in micro-segregation of elements compared with the previous reported literatures for laser welded Hastelloy C-276. High melting efficiency of ytterbium fiber laser, reduction in the amount of linear heat input, and high cooling rate of the mushy zone lead to the reduction in micro-segregation. The melting efficiency of ytterbium fiber laser for welding of Hastelloy C-276 of 64% is higher than that (48%) of conventional welding methods. High melting efficiency leads to the reduction in the linear heat input required for welding. Hence, in the present investigation, the same was found to substantially reduce as compared to the previous reported literature. The cooling rate from liquidus temperature to solidus temperature at the weld centerline was found to be in the order of 103 °C/s. Cellular dendritic substructure that constituted for lower micro-segregation was formed at the weld centerline.
关键词： laser welding,Hastelloy C-276 alloy,fiber laser,micro-segregation
更新于2025-09-12 10:27:22
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A 142 W Ho:YAG laser single-end-pumped by a Tm-doped fiber laser at 1931 nm
摘要： In this paper, a high-power Ho:YAG laser in-band pumped by a Tm-doped fiber laser at 1931 nm is reported. A maximum output power of 142.2 W is achieved at 2091 nm using a single-end-pumped configuration, corresponding to a slope efficiency of 56.7%. This is, to the best of our knowledge, the highest output power directly generated by bulk Ho-oscillators in the 2.1 μm spectral region.
关键词： fiber laser,Ho:YAG,solid state laser
更新于2025-09-12 10:27:22
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Surface transformation hardening of ductile cast iron by a 600w fiber laser
摘要： Laser transformation surface hardening of the forming edges of large mold made of nodular cast iron has gained momentum in recent years. In this investigation a 600w fiber laser was employed to harden GGG-60 cast iron. It is found that to achieve the optimum surface properties, the combination of laser power density and travel speed has to be set such that to dissolve the carbides but not that high to dissolve the graphite nodules. The response of a hardened track to a second thermal cycle by a neighboring laser track in terms of both tempering and re-hardening showed that by increasing the overlapping, a more uniform surface microstructure and hardness is obtained. In addition by employing differential scanning calorimetry (DSC) analysis the maximum “Hardening Ratio” by the fiber laser as the power source for GGG-60 cast iron was found to be 15.3 %.
关键词： Tempering,Laser Transformation Hardening,Hardening Ratio,Fiber Laser,Overlapping
更新于2025-09-12 10:27:22
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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) - Mode Re-Locking in an RF Detuned Actively Mode-Locked Fiber Ring Laser
摘要： RF detuning of the actively mode-locked ?ber ring laser (AMLL) causes deterioration in its performance due to lock-loss of higher cavity modes [1, 2]. The effects of detuning are typically mitigated by either modifying the cavity or using additional optical components [3]. We demonstrate an improvement in the performance of the detuned AMLL using multiple RF input signals without altering the cavity while achieving an extension of the injection range of the modes and increasing number of locked modes.
关键词： Lasers, injection-locked,Lasers, fiber,Laser theory,Mode-locked lasers
更新于2025-09-12 10:27:22