- 标题
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- 实验方案
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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) - A 290 W Radially Polarized Output Power from a Single-Stage Single-Crystal Yb:YAG Amplifier
摘要： Radially polarized beams exhibit interesting properties for material processing, as well as for different scientific applications such as optical trapping, plasmon excitation or data storage. With a thin-disk multipass amplifier radially polarized ultra-short pulses with an average output power of 635 W were demonstrated in [1]. For 100 W class operation, single-crystal fiber (SCF) amplifiers are an alternative approach to the thin-disk architecture. This approach reduces the costs and the complexity of the overall laser system significantly. The highest average output power demonstrated with an SCF amplifier was 160 W for a linearly polarized Gaussian seed beam [2] and 85 W for a ring-shaped radially polarized seed beam [3]. In this contribution, we present the amplification of a ring-shaped radially polarized seed beam in a single-stage SCF amplifier to an average output power of 290 W in continuous-wave (CW) operation and 270 W in femtosecond pulsed operation. This is, to the best of our knowledge, the highest average output power of a radially polarized beam demonstrated so far with an SCF amplifier.
关键词： femtosecond pulses,Radially polarized beams,high power lasers,single-crystal fiber amplifiers
更新于2025-09-11 14:15:04
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260?W of average green beam generation by intracavity frequency-doubled acousto-optic Q-Switched Nd:YAG laser
摘要： We developed an intracavity frequency-doubled acousto-optic Q-switched Nd:YAG laser generating * 260 W of average green power using two identical diode-pumped gain modules with ?vefold pumping symmetry in a simple two mirror linear cavity con?guration. The corresponding optical to optical conversion ef?ciency was estimated to be * 16.8%. At maximum output power, individual green pulse duration (FWHM) was measured to be * 73 ns with a pulse repetition rate of 18 kHz. The output average green power was highly stable with measured ?uctuation in average green power ± 0.83 W over 5 h of continuous operation. The jitter in pulse delay time and pulse to pulse amplitude ?uctuation was measured to be within ± 4.25 ns and ± 5%, respectively. The maximum beam drift recorded at 5 m distance away from the laser system was * 14 micron corresponding to beam pointing stability of ± 2.8 micro-rad.
关键词： Acousto-optic Q-switching,Intracavity frequency conversion,Diode-pumped solid-state lasers,High-power green laser
更新于2025-09-11 14:15:04
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Measurements of internal optical loss inside an operating laser diode
摘要： An experimental technique for measuring internal optical loss in high-power edge-emitting semiconductor lasers is demonstrated. The technique is based on coupling a probe beam into the waveguide of a pulse-pumped laser diode. It allows measuring free-carrier absorption (FCA) in a laser heterostructure at di?erent temperatures and at pump current levels up to 30 kA/cm2. Measurement results are presented for two laser heterostructure designs, which vary in the waveguide doping level and material. For both heterostructures, the pump current increase induces a signi?cant rise in FCA and a corresponding increase in internal optical loss, from 0.4–0.7 cm?1 at the threshold current to 2–2.5 cm?1 (65 °C, 27 kA/cm2). The gradient of the FCA current dependence is lower for the laser heterostructure with a doped GaAs waveguide, while the heterostructure with an undoped AlGaAs waveguide displays a larger increase in FCA but better internal quantum e?ciency at high currents. These results show that the proposed experimental method has signi?cant potential.
关键词： internal optical loss,heterostructure,free-carrier absorption,laser diode,high-power lasers
更新于2025-09-11 14:15:04
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Optical Smoothing with Reduced FM-to-AM Conversion in High-Power Lasers Using Spectral Distribution
摘要： High-power energetic nanosecond lasers, such as the Laser Mégajoule, require optical smoothing techniques to make their focal spots as homogeneous as possible. This strongly reduces parametric instabilities that occur during laser-plasma interaction, such as stimulated Brillouin scattering. Smoothing by spectral dispersion is one of the most-used techniques. It requires spectral broadening through phase modulation. However, because of propagation impairments, part of the phase modulation is converted into unwanted intensity modulation that induces laser nonlinearities and optical damage. This is called “FM-to-AM conversion.” Taking advantage of the architecture of the Laser Mégajoule, for which each “beam” (quadruplet) is split into four sub-beams, we show that the spectral broadening can be distributed on the sub-beams, reducing FM-to-AM conversion from 30% to 10% while maintaining smoothing performance for mitigation of stimulated Brillouin scattering.
关键词： FM-to-AM conversion,stimulated Brillouin scattering,optical smoothing,spectral distribution,high-power lasers
更新于2025-09-11 14:15:04
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[IEEE 2019 IEEE Photonics Conference (IPC) - San Antonio, TX, USA (2019.9.29-2019.10.3)] 2019 IEEE Photonics Conference (IPC) - An Efficient 4-kW Level Random Fiber Laser Based on Tandem-Pumping Scheme
摘要： In this paper, we presented a monolithic high power random fiber laser with a tandem-pumping scheme. The random fiber laser seed centered at 1064 nm was pumped by a 1018 nm fiber laser and reached an output power of 8.66 W. After the two amplifiers, the seed was amplified to 4020 W and the 3 dB width of laser spectrum was broadened from 0.78 nm to 0.99 nm. To increase the efficiency of the 4 kW laser, a specially designed high absorption coefficient (0.6 dB/m @ 1018nm) 30/250 μm Yb doped fiber and high brightness 1018 nm pump laser were adopted. The optical-to-optical efficiency could reach as high as 88.5%. No obvious mode instability was found during the experiment. Furthermore, with the same amplifier stage, we have also built another 4 kW level fiber laser seeded by an oscillator consisting of a pair of fiber Bragg gratings. The comparison of the experimental results showed that high power laser based on RFL seed would have a better control on spectral broadening.
关键词： High power,tandem-pumping,random fiber laser
更新于2025-09-11 14:15:04
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[IEEE 2019 IEEE Photonics Conference (IPC) - San Antonio, TX, USA (2019.9.29-2019.10.3)] 2019 IEEE Photonics Conference (IPC) - High-Power Mid-Infrared Quantum Cascade Semiconductor Lasers
摘要： Quantum cascade lasers (QCLs) employ intersubband transitions between conduction-band (CB) energy states in multi-quantum-well (MQW) structures, carrier tunneling between adjacent MQW stages, and coherent-light emission from multiple (30-50) stages. Unlike interband-transition semiconductor lasers, QCLs are not affected by Auger recombination in the mid-infrared wavelength range (l= 3-20 μm); thus, allowing them to readily reach lasing at room temperature (RT). However, using multiple stages leads to high voltages (3 10 V) that significantly decrease the wall-plug efficiency, hwp. Thus, although pulsed RT operation was obtained in 1996, it took until 2002 to achieve CW RT operation and until 2008 to obtain 1 W CW power.
关键词： Quantum cascade lasers,QCLs,high-power,semiconductor lasers,mid-infrared
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) - Ultrafast Tm-Doped Fiber Amplifier with 1 kW Average Output Power
摘要： Ultrafast thulium-doped fiber lasers emitting in the 2 μm wavelength region have recently attracted a significant amount of attention regarding applications in material processing, life sciences, as well as in fundamental science, e.g. high harmonic generation, particle acceleration, mid-IR generation. In addition to the application-relevant emission wavelength, Tm-doped silica fibers possess many interesting characteristics, such as a broad gain bandwidth spanning from 1700 nm to 2100 nm and more than 70% slope efficiency by exploiting cross-relaxation processes. Furthermore, the longer operation wavelength reduces the impact of detrimental nonlinear effects in fiber lasers, and allows for a larger mode field area with diffraction-limited beam quality as compared to the well-established ytterbium-doped fiber laser systems. In this contribution, we report on a new average power record from a thulium-doped fiber amplifier. We use state-of-the-art laser diodes to reach a combined pump power of more than 2 kW at 793 nm. The use of a polarization maintaining thulium-doped photonic crystal fiber allows for an optical-to-optical efficiency of more than 60% and a pump-limited average output power of 1150 W. After compression to 265 fs pulse duration, 1060 W of average power and 50 MW of peak power at 80 MHz pulse repetition rate are achieved, which represents a performance level that is currently not achievable with a single ultrafast ytterbium-doped fiber amplifier. Additionally, we confirmed a close to diffraction-limited beam quality (M2<1.1) up to the highest power level. From the simulation of the amplification process, the average heat-load of the fiber reaches 95 W/m at full power level, without the onset of transverse mode instability. This average heat-load is significantly higher than the critical value of about 30 W/m, which was found to be the threshold for transverse mode instability in ytterbium-doped fiber lasers.
关键词： ultrafast,high power,Tm-doped fiber amplifier,photonic crystal fiber
更新于2025-09-11 14:15:04
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Recent Development in Ferrite Material for High Power Application [Passive Components]
摘要： There is no doubt that power electronics is playing a critical role in the evolution of the overall infrastructure of energy supply, from motion control and drives to industry automation and traction techniques. However, unlike decades of impressive developments in semiconductor technologies, the developments in the passive components arena, especially in magnetic components, have been rather slow and have been seen as a power system bottleneck in terms of efficiency and miniaturization. To fully tap the benefits of next-generation semiconductors, namely, silicon carbide (SiC) and gallium nitride power devices, the next-generation passive components, particularly magnetic components, must be compatible with these emerging devices, especially at high frequencies and under high pulse excitation. In essence, high saturation and low-power losses under pulse excitation and relatively high temperatures are required. Current power converters using MnZn-ferrite magnetic materials possess saturation induction (Bs) levels around 530 mT at room temperature that decrease down to 430 mT at 100 °C. It is to be noted that the Bs is measured according to the IEC standard for polycrystalline ferrite under room temperature, at a field strength of 1194 A/m and 10 kHz, which is far beyond the application range. The applicable field strength varies between 100 and 200 A/m depending on the industry (aerospace, industry, and consumer electronics). Accordingly, the power losses of these materials at 1 MHz and 50 mT vary from around 350 mW/cc at room temperature to approximately 1 W/cc at 100 °C. The measuring condition is still under the sinusoidal mode.
关键词： MnZn-ferrite,power losses,ferrite material,saturation induction,high power application
更新于2025-09-10 09:29:36
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High-Periphery GaN HEMT Modeling up to 65 GHz and 200°C
摘要： In this article, we report on the temperature-dependent GaN HEMT behavior. To evaluate the potentialities of this kind of active solid-state electronic device at its best, the experiments are performed at extreme operating conditions. As a case study, we consider a large 0.25-μm GaN HEMT with a gate periphery of 1.5 mm, providing a high dissipated power of 5.1 W. The tested semiconductor device is characterized by measuring scattering parameters at high frequencies up to 65 GHz and at high ambient temperature up to 200°C. To assess the impact of the thermal effects on high-frequency GaN HEMT performance, an equivalent circuit is analytically extracted and then used to determine the main RF figures of merit. The achieved experimental results show evidence that the increase of the temperature causes a significant degradation in device performance.
关键词： scattering parameter measurements,high-power,GaN HEMT,high-temperature,Active solid-state electronic device,millimeter-wave frequency
更新于2025-09-10 09:29:36
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Relativistic microwave oscillators with high power flux in a free space and interaction zone
摘要： In the recent two decades, high-power microwave (HPM) generators producing short Ka-band and X-band pulses were intensively investigated (see Refs. [1–6] and citation therein). For generation of HPM pulses with duration of units of nanosecond and less influence of microwave breakdowns of electrodynamics systems, expansion of cathode and collector plasmas, and electron beam structure distortions becomes insignificant. Though the pulse duration is short, the radiating energy rises if coherent summation of radiation from several generators is provided. When the power in each channel is high, the wave beam could be formed where power flux density is limited only by breakdown strength of the media. Using approaches of the phased arrays, the directional pattern (DP) of summarized radiation could be steered. This is achievable from pulse to pulse, as well as during a single nanosecond pulse if summarized wave beams have a shifted frequencies. The related experiments with Ka-band microwave pulses are presented below.
关键词： directional pattern,Ka-band,phased arrays,superradiance,microwave breakdowns,backward-wave oscillators,X-band,coherent summation,high-power microwave
更新于2025-09-10 09:29:36