- 标题
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- 实验方案
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Investigation of the influence of welding parameters on the weld geometry when welding structural steel with oscillated high-power laser beam
摘要： Oscillation of the laser beam has been applied to achieve a positive influence on the efficiency of the welding process and the quality of the weld seam. In this work a 10 kW laser beam from a fiber laser was oscillated with frequencies up to 1000 Hz for bead on plate welds in 15 mm thick structural steel to investigate the influence of beam oscillation on geometrical dimensions of the weld seam. The laser beam was oscillated transversally with a given amplitude for each frequency. The parameter set to be varied was laser power, welding speed and focal point position according to the highest influence on the formation of the weld seam and the welding process. The results obtained show that lower oscillation frequencies in the range of 200 Hz with higher amplitudes in combination with either low welding speeds or higher laser powers up to 10 kW had the greatest influence on the geometry of the weld seam.
关键词： fibre laser,transversal scanning,structural steel,oscillating laser beam,high power laser
更新于2025-09-12 10:27:22
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Effect of peak power enhancement of ferrite phase shifter from full-height to increased-height rectangular waveguide
摘要： In order to enhance the high-power performance of the ferrite phase shifter (PS), a method of increasing waveguide height is proposed and experimentally demonstrated. Dual-toroid geometry is utilized as a high-power structure. Two configurations of X-band PSs with full-height (FH) and increased-height (IH) waveguides are designed and fabricated while keeping other parameters consistent. Comparative analysis based on simulation and high-power experiments is conducted. The simulation results agree well with experiments. Compared with the FHPS, the IHPS can enhance the peak-power-capacity from 90 kW to 140 kW while maintaining almost the same insertion loss of 0.5 dB with a slight increase in differential phase shift from 360○ to 380○.
关键词： waveguide height,X-band,dual-toroid geometry,ferrite phase shifter,high-power performance
更新于2025-09-12 10:27:22
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A double-layer white light converter with high efficiency heat transfer structure for high-power NUV LEDs/LDs
摘要： As a next-generation lighting technology, high-power light-emitting diodes (LEDs) and lasing diodes (LDs) lighting have attracted great attention to high-brightness applications. However, producing an efficient illumination-grade color converter with a conspicuous color rendering index (CRI) and a suitable correlated color temperature (CCT) remains an outstanding challenge in the field of high-power LEDs/LDs lighting. In this work, a double-layer white light converter with high efficiency heat transfer structure was designed and prepared by precisely coating a blue/green emitting phosphor-in-silicone (PIS) film on red emitting transparent ceramic substrate. The well-designed double-layer converter exhibits excellent optical properties that the optical-optical conversion efficiency can achieve 156 lm/W with conspicuous CRI (92.6), CIE chromaticity coordinate (0.332, 0.335) and suitable CCT (5511K), respectively. Furthermore, the heat transfer efficiency of the double-layer converter was analyzed and simulated by using infrared thermal imaging and steady state thermal simulation, which reduce the temperature efficiently than single-layer converter under high-power NUV LEDs/LDs excitation. These comprehensive performance show that the double-layer converters are promising as NUV LEDs/LDs-driven phosphors in high-power solid-state lighting devices.
关键词： high-power LED/LD,transparent ceramic,white light converter,thermal performance,double-layer structure
更新于2025-09-12 10:27:22
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170 mW-level mode-locked Er-doped fiber laser oscillator based on nonlinear polarization rotation
摘要： In our work, by optimizing the length of the cavity and using high-power home-made pump source, based on the commonly-used nonlinear polarization rotation (NPR) technique, we designed a stable all-fiber high-power Er-doped mode-locked laser successfully. The maximum average output power was as high as 174 mW under the pump power of 2659 mW. To our knowledge, 174 mW was a new record average output power of NPR based all-fiber mode-locked Er-doped fiber laser, which was much higher than the results reported previously. Our work will provide a significant reference for future demonstrations of high-power mode-locked Er-doped fiber lasers and promote the applications of mode-locked Er-doped oscillators.
关键词： Er-doped fiber laser,mode-locked,high-power,nonlinear polarization rotation
更新于2025-09-12 10:27:22
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Avoidance of end crater imperfections at high-power laser beam welding of closed circumferential welds
摘要： The present work deals with the development of a strategy for the prevention of end crater defects in high-power laser welding of thick-walled circumferential welds. A series of experiments were performed to understand the influence of the welding parameters on the formation of end crater defects such as pores, cracks, root excess weld metal and shrinkage cavities in the overlap area. An abrupt switch-off of the laser power while closing the circumferential weld leads to a formation of a hole which passes through the whole welded material thickness. A laser power ramp-down causes solidification cracks which are initiated on the transition from full-penetration mode to partial penetration. Defocusing the laser beam led to promising results in terms of avoiding end crater defects. Cracks and pores in the overlap area could be effectively avoided by using defocusing techniques. A strategy for avoiding of end crater imperfections was tested on flat specimens of steel grade S355 J2 with a wall thickness of between 8 and 10 mm and then transferred on the 10 mm thick pipe sections made of high-strength pipeline steel API5L-X100Q.
关键词： Thick-walled pipes,End crater,Circumferential weld,High-power laser beam,Laser beam welding
更新于2025-09-12 10:27:22
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A Waveguide Switch Based on Contactless Gap Waveguide Technology
摘要： A novel dual-pole dual-throw (DPDT) waveguide switch is proposed for high-power and low-loss applications. The proposed DPDT was designed based on the contactless properties of the gap waveguide technologies in the Ku frequency band. The DPDT was composed of two concentric contactless cylinders. Standard rectangular waveguide ports (WR 75) and waveguide paths are machined in the middle of these cylinders. The rotational movement of the inner cylinder is realized using two bearings in the top and bottom of the DPDT. The proposed structure is fabricated and the measured results are in good agreement with the simulated ones. The measured insertion loss and return loss for the aligned ports are better than 0.1 and 25 dB in the frequency band ranging from 11 to 13.5 GHz, respectively, and the measured isolation between two adjacent ports is better than 60 dB.
关键词： gap waveguide,Dual-pole dual-throw (DPDT),high-power applications,waveguide switch
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) - Thin-Disk Laser Emitting Beams with 980 W of CW-Output Power and Radial Polarization
摘要： Within the past decade, a variety of scientific groups have demonstrated the potential of radially and azimuthally polarized laser beams in many applications [1-3]. Experimental investigations in high-power operation indicate additional beneficial properties for material processing, such as drilling and deep-penetration-welding, which have been demonstrated to lead to an increase of the process efficiency by using such a polarization state. Cutting of metal sheets with radially polarized beams at 1 micron wavelength have been reported recently to increase the process efficiency [4]. In the present work, we report on the generation of radially polarized laser beams in cw operation by using grating-waveguide mirror (GWM) [5]. The grating design is based on the leaky-mode coupling mechanism, which allows for sufficient reduction of the reflectivity of the polarization state (azimuthal or radial) to be suppressed in the resonator. It consists of a circular sub-wavelength diffraction grating integrated into a highly or partially reflective dielectric multilayer mirror. At the central wavelength of the Yb:LuAG TDL, i.e., at 1030 nm, the absolute values of the reflectivities for the TE- and TM-polarized light were measured to be (55.2 ± 0.2)% and (99.8 ± 0.2)%, respectively. This corresponds to a reflectivity difference of approximately 45%. At wavelengths of 1023, 1042, and 1059 nm, the reflectivity of the TE-polarized beam was measured to be <1%, making the grating attractive for other applications with lasers operating within this wavelength range. The grating was implemented as cavity end mirror in an Yb:LuAG thin-disk laser setup, pumped at its “zero-phonon” line, i.e. λ = 969 nm. The implementation of the GWM led to the extraction of a radially polarized beam with an output power of 980 W and an optical efficiency of 50.5%. Single transversal mode operation of a radially polarized LG01 mode was sustained for the whole output power range with beam quality factors of Mx2 = 2.0 and My2 = 2.3. Figure 1(a) shows a photograph of the GWM. In Fig. 1(b), the performance of the laser and the far field intensity distribution of the emitted laser beam is shown. A qualitative analysis of the polarization was carried out by recording the intensity distributions transmitted through a rotating polarizer at different orientations of its transmission axis. Furthermore, the purity of polarization (degree of polarization) was measured with a custom-made camera-based 2D Stokes-polarimeter. An average degree of radial polarization of 95% was measured.
关键词： grating-waveguide mirror,high-power operation,radially polarized laser beams,material processing,Yb:LuAG thin-disk laser
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) - Narrower Far Field and Higher Efficiency in 1 kW Diode-Laser Bars using Improved Lateral Structuring
摘要： High power, efficient diode-laser bars with narrow far field angles are sought for many applications, for example in the 9xx nm-range for the pumping of Yb:YAG disc and slab lasers. In previous work, broad-area (BA) diode-laser bars with 4 mm resonator length operated with high conversion efficiency η = 62% at operating power Pop = 1 kW in quasi-continuous wave testing (200 μs, 10 Hz), by using low optical loss and low-resistivity vertical structures and high fill-factors (~70%). Lateral far field (95% power) was θ95% > 10°. However, higher η and narrower θ95% are needed for industrial application, and we seek improvements by altering the lateral bar structure for a fixed vertical design (from [1], wavelength λ = 930 nm, loss αi ≈ 0.4 cm-1). First, narrower θ95% at Pop = 1 kW was sought. In previous studies on 90 μm-wide single emitters, deep implantation through the active region was shown to reduce gain at the emitter edges, suppressing higher-order lateral modes, for smaller θ95%, at the price of reduced η and Pop. A similar implantation approach is assessed here in high fill-factor bars, and the drop in η is mitigated by reducing the implantation depth. Second, higher η at Pop = 1 kW was sought, by increasing the fill-factor, for lower electrical resistance.
关键词： lateral structuring,efficiency,narrow far field,high power,diode-laser bars
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) - Thin Disk Laser Operating in Fundamental Mode up to a Power of 4kW
摘要： Fundamental mode lasers at high power are desirable to accommodate many industrial and scientific applications especially in pulsed mode of operation. Due to its unique properties the thin disk laser (TDL) concept is an ideal platform for the generation of high optical power with excellent beam quality. Reliability, low brightness constraints for the pump source, insensitivity to back reflections, negligible nonlinearities, high scalability are a few inherent properties, and thus TDLs have been widely used in industrial applications. In the past there have been many efforts to reach the maximum output power keeping the beam quality close to the diffraction limit. Here we report on an enhanced system reaching 4 kW output power with a beam quality M2<1.2 over the full power range. The experimental setup consists of a multipass pump chamber which enables 22 passes through the active laser disk, two convex high-reflection (HR) mirrors, a spherically deformable mirror (SDM), an Yb-doped laser disk mounted on a heat sink and an outcoupling (OC) mirror. The OC is shaped such that static aspherical wavefront aberrations originating from the laser disk can be compensated. Using this approach, we demonstrate a 4 kW diffraction limited building block. Further power scaling can be achieved by using conventional combining methods such as polarization beam combining, spatial beam combining or disk multipass amplification.
关键词： high power,beam quality,thin disk laser,fundamental mode,diffraction limit
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) - Monolithic Master Oscillator with Tapered Power Amplifier Diode Laser at 1060 nm with Additional Control Section for High Power Operation
摘要： State of the art diode laser light sources for high power operation with good beam quality are distributed Bragg reflector tapered diode lasers (DBR-TPLs). These devices deliver over 10 W of spectrally narrowband emission within an almost diffraction-limited beam [1]. However, due to the integration of the tapered section into the resonator, these devices are designed that only a forward traveling wave is optimal confined and amplified. This trade-off limits the potential of these devices. One way to overcome this limitation is to move the tapered section outside of the resonator and use as a single pass power amplifier in a monolithic master oscillator power amplifier (MOPA) layout [2]–[4]. However, the benefits on the emissions characteristics, as discussed below, of these devices can diminish if multi-cavity operation occurs. In this work, we present results on recently developed monolithic MOPAs for enhanced suppression of multi-cavity operation. The MOs in these devices are 2 mm long with a 7th order DBR grating at the front- and backside and a 0.75 mm long active section in the middle. An active 0.5 mm long control section (CON) follows the MO section. Both have a ridge waveguide (RW) width of 5 μm. The PA section is 3.5 mm long and defined by the tapered p-side contact with a full angle of 6°. The 3 different layouts are depicted in Fig. 1 a). In the first layout (top) all three section are in a straight line perpendicular to the front facet. The second layout (middle) has a MO section tilted by 4° and a bent CON section and the third layout (bottom) has bent CON section and a PA section tilted by 4°. Fig. 1 a) Sketch of all three monolithic MOPA layouts. b) Optical output power (solid lines) and the peak wavelength (dots) for three different monolithic MOPAs. The straight layout is used as reference to discuss the benefits of a bent control section and either a tilted MO or tilted PA on the emission characteristics of the devices. Furthermore the influence of the control section on the emission characteristics of the devices will be presented. This includes a comparison of the optical output power, the spectra and the beam quality factor of the devices. All devices provide over 6 W of optical output power at 1060 nm within a narrow spectral bandwidth below 17 pm (spectrometer resolution limit). However the overall emission characteristics have clear differences as can be seen in Fig. 1 b). Here the optical output power and the peak wavelength are plotted in dependence of the PA current. The laser with the tilted MO layout shows a small increase in output power compared to the straight layout and a reduction of spectral mode jumps for PA currents below IPA = 8 A. For the laser with the tilted PA layout the small spectral mode jumps due to multi-cavity operation are completely suppressed but the output power is reduced by 0.5 W.
关键词： MOPA,spectral bandwidth,diode laser,monolithic master oscillator power amplifier,high power operation,beam quality
更新于2025-09-11 14:15:04