Contents 1 Issue (s), 13 Article (s)

Vol.9, Iss.3—Jan.1, 2021 • pp: e35- Spec. pp:

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Vol.9, Iss.3-Jul..1,2021
Research Articles
Diamond Raman laser: a promising high-beam-quality and low-thermal-effect laser
Yulan Li, Jie Ding, Zhenxu Bai, Xuezong Yang, Yuqi Li, Jingling Tang, Yu Zhang, Yaoyao Qi, Yulei Wang, and Zhiwei Lu
Stimulated Raman-scattering-based lasers provide an effective way to achieve wavelength conversion. However, thermally induced beam degradation is a notorious obstacle to power scaling and it also limits the applicable range where high output beam quality is needed. Considerable research efforts have been devoted to developing Raman materials, with diamond being a promising candidate to acquire wavelength-versatile, high-power, and high-quality output beam owing to its excellent thermal properties, high Raman gain coefficient, and wide transmission range. The diamond Raman resonator is usually designed as an external-cavity pumped structure, which can easily eliminate the negative thermal effects of intracavity laser crystals. Diamond Raman converters also provide an approach to improve the beam quality owing to the Raman cleanup effect. This review outlines the research status of diamond Raman lasers, including beam quality optimization, Raman conversion, thermal effects, and prospects for future development directions.
High Power Laser Science and Engineering
  • Publication Date: Jan. 01, 1900
  • Vol.9 Issue, 3 03000e35 (2021)
Research Articles
Optimizing noise characteristics of mode-locked Yb-doped fiber laser using gain-induced RIN-transfer dynamics
Jiangshuoxue Han, Yang Liu, Zejiang Deng, Gehui Xie, Daping Luo, Chenglin Gu, Lian Zhou, and Wenxue Li
High Power Laser Science and Engineering
  • Publication Date: Jan. 01, 1900
  • Vol.9 Issue, 3 03000e36 (2021)
Research Articles
Control of amorphous solid water target morphology induced by deposition on a charged surface
Alexander Bespaly, Indranuj Dey, Jenya Papeer, Assaf Shaham, Pavel Komm, Ibrahim Hadad, Gilad Marcus, and Arie Zigler
Microstructured targets demonstrate an enhanced coupling of high-intensity laser pulse to a target and play an important role in laser-induced ion acceleration. Here we demonstrate an approach that enables us to control the morphology of amorphous solid water (ASW) microstructured targets, by deposition of water vapor on a charged substrate, cooled down to 100 K. The morphology of the deposited ASW structures is controlled by varying the surface charge on the substrate and the pressure of water vapor. The obtained target is structured as multiple, dense spikes, confined by the charged area on the substrate, with increased aspect ratio of up to 5:1 and having a diameter comparable with the typical spot size of the laser focused onto the target.
High Power Laser Science and Engineering
  • Publication Date: Jan. 01, 1900
  • Vol.9 Issue, 3 03000e37 (2021)
Research Articles
High-energy, high-repetition-rate ultraviolet pulses from an efficiency-enhanced, frequency-tripled laser
Xinlin Lü, Yujie Peng, Wenyu Wang, Yuanan Zhao, Xiangyu Zhu, and Yuxin Leng
In this study, a high-energy, temporally shaped picosecond ultraviolet (UV) laser running at 100 Hz is demonstrated, with its pulses boosted to 120 mJ by cascaded regenerative and double-pass amplifiers, resulting in a gain of more than 108. With precise manipulation and optimization, the amplified laser pulses were flat-top in the temporal and spatial domains to maintain high filling factors, which significantly improved the conversion efficiency of the subsequent third harmonic generation (THG). Finally, 91 mJ, 470 ps pulses were obtained at 355 nm, corresponding to a conversion efficiency as high as 76%, which, as far as we are aware of, is the highest THG efficiency for a high-repetition-rate picosecond laser. In addition, the energy stability of the UV laser is better than 1.07% (root mean square), which makes this laser an attractive source for a variety of fields including laser conditioning and micro-fabrication.
High Power Laser Science and Engineering
  • Publication Date: Jan. 01, 1900
  • Vol.9 Issue, 3 03000e38 (2021)
Research Articles
Utilizing phase-shifted long-period fiber grating to suppress spectral broadening of a high-power fiber MOPA laser system
Yinxu Bian, Kerong Jiao, Xuecheng Wu, Hua Shen, Feiyan Yang, and Rihong Zhu
Suppressing nonlinear effects in high-power fiber lasers based on fiber gratings has become a hotspot. At present, research is mainly focused on suppressing stimulated Raman scattering in a high-power fiber laser. However, the suppression of spectral broadening, caused by self-phase modulation or four-wave mixing, is still a challenging attribute to the close distance between the broadened laser and signal laser. If using a traditional fiber grating with only one stopband to suppress the spectral broadening, the signal power will be stripped simultaneously. Confronting this challenge, we propose a novel method based on phase-shifted long-period fiber grating (PS-LPFG) to suppress spectral broadening in a high-power fiber master oscillator power amplifier (MOPA) laser system in this paper. A PS-LPFG is designed and fabricated on 10/130 passive fiber utilizing a point-by-point scanning technique. The resonant wavelength of the fabricated PS-LPFG is 1080 nm, the full width at half maximum of the passband is 5.48 nm, and stopband extinction exceeds 90%. To evaluate the performance of the PS-LPFG, the grating is inserted into the seed of a kilowatt-level continuous-wave MOPA system. Experiment results show that the 30 dB linewidth of the output spectrum is narrowed by approximately 37.97%, providing an effective and flexible way for optimizing the output linewidth of high-power fiber MOPA laser systems.
High Power Laser Science and Engineering
  • Publication Date: Jan. 01, 1900
  • Vol.9 Issue, 3 03000e39 (2021)
Research Articles
Time-dependent measurement of high-power laser light reflection by low-Z foam plasma
M. Cipriani, S. Yu. Gus’kov, F. Consoli, R. De Angelis, A. A. Rupasov, P. Andreoli, G. Cristofari, G. Di Giorgio, and M. Salvadori
Porous materials have many applications for laser–matter interaction experiments related to inertial confinement fusion. Obtaining new knowledge about the properties of the laser-produced plasma of porous media is a challenging task. In this work, we report, for the first time to the best of our knowledge, the time-dependent measurement of the reflected light of a terawatt laser pulse from the laser-produced plasma of low-Z foam material of overcritical density. The experiments have been performed with the ABC laser, with targets constituted by foam of overcritical density and by solid media of the same chemical composition. We implemented in the MULTI-FM code a model for the light reflection to reproduce and interpret the experimental results. Using the simulations together with the experimental results, we indicate a criterion for estimating the homogenization time of the laser-produced plasma, whose measurement is challenging with direct diagnostic techniques and still not achieved.
High Power Laser Science and Engineering
  • Publication Date: Jan. 01, 1900
  • Vol.9 Issue, 3 03000e40 (2021)
Research Articles
A 3.5-kW near-single-mode oscillating–amplifying integrated fiber laser
Lingfa Zeng, Xiaolin Wang, Baolai Yang, Hanwei Zhang, and Xiaojun Xu
The fiber laser based on an oscillating-amplifying integrated structure has the potential to benefit from the advantages of a fiber laser oscillator and amplifier with the characteristics of strong anti-back-reflected light ability and high efficiency. Here, we achieved a 3.5-kW near-single-mode (M2 ∼ 1.24) oscillating–amplifying integrated fiber laser with an active fiber length of 8 m in the oscillating section and 17.6 m in the amplifying section. While operating at the maximum power, the optical-to-optical conversion efficiency is 87.0%, and the intensity of stimulated Raman scattering is about 23.61 dB lower than that of the signal light. To the best of the authors’ knowledge, this is the highest output power of an oscillating–amplifying integrated fiber laser, accompanied with the best beam quality and the highest efficiency.
High Power Laser Science and Engineering
  • Publication Date: Jan. 01, 1900
  • Vol.9 Issue, 3 03000e41 (2021)
Research Articles
High-resolution X-ray flash radiography of Ti characteristic lines with multilayer Kirkpatrick–Baez microscope at the Shenguang-II Update laser facility
Shengzhen Yi, Feng Zhang, Qiushi Huang, Lai Wei, Yuqiu Gu, and Zhanshan Wang
High-resolution X-ray flash radiography of Ti characteristic lines with a multilayer Kirkpatrick–Baez microscope was developed on the Shenguang-II (SG-II) Update laser facility. The microscope uses an optimized multilayer design of Co/C and W/C stacks to obtain a high reflection efficiency of the Ti characteristic lines while meeting the precise alignment requirement at the Cu Kα line. The alignment method based on dual simulated balls was proposed herein, which simultaneously realizes an accurate indication of the center field of view and the backlighter position. The optical design, multilayer coatings, and alignment method of the microscope and the experimental result of Ti flash radiography of the Au-coned CH shell target on the SG-II Update are described.
High Power Laser Science and Engineering
  • Publication Date: Jan. 01, 1900
  • Vol.9 Issue, 3 03000e42 (2021)
Research Articles
Efficient bright γ-ray vortex emission from a laser-illuminated light-fan-in-channel target
Hao Zhang, Jie Zhao, Yanting Hu, Qianni Li, Yu Lu, Yue Cao, Debin Zou, Zhengming Sheng, Francesco Pegoraro, Paul McKenna, Fuqiu Shao, and Tongpu Yu
X/γ-rays have many potential applications in laboratory astrophysics and particle physics. Although several methods have been proposed for generating electron, positron, and X/γ-photon beams with angular momentum (AM), the generation of ultra-intense brilliant γ-rays is still challenging. Here, we present an all-optical scheme to generate a high-energy γ-photon beam with large beam angular momentum (BAM), small divergence, and high brilliance. In the first stage, a circularly polarized laser pulse with intensity of 1022 W/cm2 irradiates a micro-channel target, drags out electrons from the channel wall, and accelerates them to high energies via the longitudinal electric fields. During the process, the laser transfers its spin angular momentum (SAM) to the electrons’ orbital angular momentum (OAM). In the second stage, the drive pulse is reflected by the attached fan-foil and a vortex laser pulse is thus formed. In the third stage, the energetic electrons collide head-on with the reflected vortex pulse and transfer their AM to the γ-photons via nonlinear Compton scattering. Three-dimensional particle-in-cell simulations show that the peak brilliance of the γ-ray beam is $\sim 1{0}^{22}$ photons·s–1·mm–2·mrad–2 per 0.1% bandwidth at 1 MeV with a peak instantaneous power of 25 TW and averaged BAM of $1{0}^6\hslash$/photon. The AM conversion efficiency from laser to the γ-photons is unprecedentedly 0.67%.
High Power Laser Science and Engineering
  • Publication Date: Jan. 01, 1900
  • Vol.9 Issue, 3 03000e43 (2021)
Research Articles
Direct acceleration of an annular attosecond electron slice driven by near-infrared Laguerre–Gaussian laser
C. Jiang, W. P. Wang, S. Weber, H. Dong, Y. X. Leng, R. X. Li, and Z. Z. Xu
A new near-infrared direct acceleration mechanism driven by Laguerre–Gaussian laser is proposed to stably accelerate and concentrate electron slice both in longitudinal and transversal directions in vacuum. Three-dimensional simulations show that a 2-μm circularly polarized ${\mathrm{LG}}_p^l$ (p = 0, l = 1, σz = -1) laser can directly manipulate attosecond electron slices in additional dimensions (angular directions) and give them annular structures and angular momentums. These annular vortex attosecond electron slices are expected to have some novel applications such as in the collimation of antiprotons in conventional linear accelerators, edge-enhancement electron imaging, structured X-ray generation, and analysis and manipulation of nanomaterials.
High Power Laser Science and Engineering
  • Publication Date: Jan. 01, 1900
  • Vol.9 Issue, 3 03000e44 (2021)
Research Articles
All-fiberized and narrow-linewidth 5 kW power-level fiber amplifier based on a bidirectional pumping configuration
Pengfei Ma, Hu Xiao, Wei Liu, Hanwei Zhang, Xiaolin Wang, Jinyong Leng, and Pu Zhou
In this paper, an all-fiberized and narrow-linewidth 5 kW power-level fiber amplifier is presented. The laser is achieved based on the master oscillator power amplification configuration, in which the phase-modulated single-frequency laser is applied as the seed laser and a bidirectional pumping configuration is applied in the power amplifier. The stimulated Brillouin scattering, stimulated Raman scattering, and transverse mode instability effects are all effectively suppressed in the experiment. Consequently, the output power is scaled up to 4.92 kW with a slope efficiency of as high as approximately 80%. The 3-dB spectral width is about 0.59 nm, and the beam quality is measured to be M2∼1.22 at maximum output power. Furthermore, we have also conducted a detailed spectral analysis on the spectral width of the signal laser, which reveals that the spectral wing broadening phenomenon could lead to the obvious decrease of the spectral purity at certain output power. Overall, this work could provide a reference for obtaining and optimizing high-power narrow-linewidth fiber lasers.
High Power Laser Science and Engineering
  • Publication Date: Jan. 01, 1900
  • Vol.9 Issue, 3 03000e45 (2021)
Research Articles
Spectral filtering effect on multi-pulsing induced by chirped fiber Bragg grating in dispersion-managed mode-locked Yb-doped fiber lasers
Dongyu Yan, Bowen Liu, Defeng Zou, Jie Guo, Yuxi Chu, Youjian Song, and Minglie Hu
We numerically and experimentally investigate the multi-pulsing mechanism in a dispersion-managed mode-locked Yb-doped fiber laser. Multi-pulsing occurs primarily owing to the inherent filtering effect of the chirped fiber Bragg grating. The spectral filtering effect restricts the spectral broadening induced by self-phase modulation and causes extra loss, leading to a decreased pump power threshold for the multi-pulsing state. Numerical simulations show that multi-pulsing emerges at a lower pump power when the spectral filter bandwidth becomes narrower. In the experiment, the spectral width increases as the net cavity dispersion approaches zero. Pulses with wider spectral widths experience more loss from the spectral filtering effect, leading to a decreased pump power threshold for multi-pulsing. Therefore, the net cavity dispersion also has an impact on the multi-pulsing threshold. Based on this conclusion, we devise a strategy to obtain single-pulsing operation with the shortest pulse width and the highest pulse energy.
High Power Laser Science and Engineering
  • Publication Date: Jan. 01, 1900
  • Vol.9 Issue, 3 03000e46 (2021)
Research Articles
Shock dynamics and shock collision in foam layered targets
K. Batani, A. Aliverdiev, R. Benocci, R. Dezulian, A. Amirova, E. Krousky, M. Pfeifer, J. Skala, R. Dudzak, W. Nazarov, and D. Batani
We present an experimental study of the dynamics of shocks generated by the interaction of a double-spot laser in different kinds of targets: simple aluminum foils and foam–aluminum layered targets. The experiment was performed using the Prague PALS iodine laser working at 0.44 μm wavelength and irradiance of a few 1015 W/cm2. Shock breakouts for pure Al and for foam-Al targets have been recorded using time-resolved self-emission diagnostics. Experimental results have been compared with numerical simulations. The shocks originating from two spots move forward and expand radially in the targets, finally colliding in the intermediate region and producing a very strong increase in pressure. This is particularly clear for the case of foam layered targets, where we also observed a delay of shock breakout and a spatial redistribution of the pressure. The influence of the foam layer doped with high-Z (Au) nanoparticles on the shock dynamics was also studied.
High Power Laser Science and Engineering
  • Publication Date: Jan. 01, 1900
  • Vol.9 Issue, 3 03000e47 (2021)