Contents
2018
Volume: 6 Issue 4
13 Article(s)

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Special Issue on Focus on National Laboratory of High Power Laser and Physics, SIOM
Status and development of high-power laser facilities at the NLHPLP
Jianqiang Zhu, Jian Zhu, Xuechun Li, Baoqiang Zhu, Weixin Ma, Xingqiang Lu, Wei Fan, Zhigang Liu, Shenlei Zhou, Guang Xu, Guowen Zhang, Xinglong Xie, Lin Yang, Jiangfeng Wang, Xiaoping Ouyang, Li Wang, Dawei Li, Pengqian Yang, Quantang Fan, Mingying Sun, Chong Liu, Dean Liu, Yanli Zhang, Hua Tao, Meizhi Sun, Ping Zhu, Bingyan Wang, Zhaoyang Jiao, Lei Ren, Daizhong Liu, Xiang Jiao, Hongbiao Huang, and Zunqi Lin
In this paper, we review the status of the multifunctional experimental platform at the National Laboratory of High Power Laser and Physics (NLHPLP). The platform, including the SG-II laser facility, SG-II 9th beam, SG-II upgrade (SG-II UP) facility, and SG-II 5 PW facility, is operational and available for interested scientists studying inertial confinement fusion (ICF) and a broad range of high-energy-density physics. These facilities can provide important experimental capabilities by combining different pulse widths of nanosecond, picosecond, and femtosecond scales. In addition, the SG-II UP facility, consisting of a single petawatt system and an eight-beam nanosecond system, is introduced including several laser technologies that have been developed to ensure the performance of the facility. Recent developments of the SG-II 5 PW facility are also presented.
High Power Laser Science and Engineering
  • Publication Date: Nov. 16, 2018
  • Vol.6 Issue, 4 04000e55 (2018)
Special Issue on High Energy Density Physics and High Power Lasers 2018
Design and experimental demonstration of a high conversion efficiency OPCPA pre-amplifier for petawatt laser facility
Xiao Liang, Xinglong Xie, Jun Kang, Qingwei Yang, Hui Wei, Meizhi Sun, and Jianqiang Zhu
We present the design and experiment of a broadband optical parametric chirped-pulse amplifier (OPCPA) which provides high conversion efficiency and good beam quality at 808 nm wavelength. Using a three-dimensional spatial and temporal numerical model, several design considerations necessary to achieve high conversion efficiency, good beam quality and good output stability are discussed. To improve the conversion efficiency and broaden the amplified signal bandwidth simultaneously, the nonlinear crystal length and OPCPA parameters are analyzed and optimized with the concept of dissipating amplified idler between optical parametric amplification (OPA) of two crystals configuration. In the experiment, an amplifier consisting of two OPCPA stages of ‘L’ type configuration was demonstrated by using the optimized parameters. An amplified signal energy of 160 mJ was achieved with a total pump-to-signal efficiency of 35% (43% efficiency for the OPCPA stage 2). The output bandwidth of signal pulse reached 80 nm and the signal pulse was compressed to 24 fs. The energy stability reached 1.67% RMS at 3% pump energy variation. The optimized OPCPA amplifier operates at a repetition rate of 1 Hz and is used as a front-end injection for the main amplifier of SG-II 5PW laser facility.
High Power Laser Science and Engineering
  • Publication Date: Nov. 22, 2018
  • Vol.6 Issue, 4 04000e58 (2018)
Single-shot cross-correlator for pulse-contrast characterization of high peak-power lasers
Jingui Ma, Peng Yuan, Jing Wang, Guoqiang Xie, Heyuan Zhu, and Liejia Qian
Pulse contrast is a crucial parameter of high peak-power lasers since the prepulse noise may disturb laser–plasma interactions. Contrast measurement is thus a prerequisite to tackle the contrast challenge in high peak-power lasers. This paper presents the progress review of single-shot cross-correlator (SSCC) for real-time contrast characterization. We begin with the key technologies that enable an SSCC to simultaneously possess high dynamic range (), large temporal window (50–70 ps) and high fidelity. We also summarize the instrumentation of SSCC prototypes and their applications on five sets of petawatt laser facilities in China. Finally, we discuss how to extend contrast measurements from time domain to spatiotemporal domain. Real-time and high-dynamic-range contrast measurements, provided by SSCC, can not only characterize various complex noises in high peak-power lasers but also guide the system optimization.
High Power Laser Science and Engineering
  • Publication Date: Dec. 18, 2018
  • Vol.6 Issue, 4 04000e61 (2018)
Overview of ytterbium based transparent ceramics for diode pumped high energy solid-state lasers
Samuel Paul David, Venkatesan Jambunathan, Antonio Lucianetti, and Tomas Mocek
High Power Laser Science and Engineering
  • Publication Date: Dec. 18, 2018
  • Vol.6 Issue, 4 04000e62 (2018)
Development of a 100 J, 10 Hz laser for compression experiments at the High Energy Density instrument at the European XFEL
Paul Mason, Saumyabrata Banerjee, Jodie Smith, Thomas Butcher, Jonathan Phillips, Hauke Höppner, Dominik Möller, Klaus Ertel, Mariastefania De Vido, Ian Hollingham, Andrew Norton, Stephanie Tomlinson, Tinesimba Zata, Jorge Suarez Merchan, Chris Hooker, Mike Tyldesley, Toma Toncian, Cristina Hernandez-Gomez, Chris Edwards, and John Collier
In this paper we review the design and development of a 100 J, 10 Hz nanosecond pulsed laser, codenamed DiPOLE100X, being built at the Central Laser Facility (CLF). This 1 kW average power diode-pumped solid-state laser (DPSSL) is based on a master oscillator power amplifier (MOPA) design, which includes two cryogenic gas cooled amplifier stages based on DiPOLE multi-slab ceramic Yb:YAG amplifier technology developed at the CLF. The laser will produce pulses between 2 and 15 ns in duration with precise, arbitrarily selectable shapes, at pulse repetition rates up to 10 Hz, allowing real-time shape optimization for compression experiments. Once completed, the laser will be delivered to the European X-ray Free Electron Laser (XFEL) facility in Germany as a UK-funded contribution in kind, where it will be used to study extreme states of matter at the High Energy Density (HED) instrument.
High Power Laser Science and Engineering
  • Publication Date: Dec. 19, 2018
  • Vol.6 Issue, 4 04000e65 (2018)
Special Issue on Laboratory Astrophysics
Experimental methods for warm dense matter research | On the Cover
Katerina Falk
The study of structure, thermodynamic state, equation of state (EOS) and transport properties of warm dense matter (WDM) has become one of the key aspects of laboratory astrophysics. This field has demonstrated its importance not only concerning the internal structure of planets, but also other astrophysical bodies such as brown dwarfs, crusts of old stars or white dwarf stars. There has been a rapid increase in interest and activity in this field over the last two decades owing to many technological advances including not only the commissioning of high energy optical laser systems, z-pinches and X-ray free electron lasers, but also short-pulse laser facilities capable of generation of novel particle and X-ray sources. Many new diagnostic methods have been developed recently to study WDM in its full complexity. Even ultrafast nonequilibrium dynamics has been accessed for the first time thanks to subpicosecond laser pulses achieved at new facilities. Recent years saw a number of major discoveries with direct implications to astrophysics such as the formation of diamond at pressures relevant to interiors of frozen giant planets like Neptune, metallic hydrogen under conditions such as those found inside Jupiter’s dynamo or formation of lonsdaleite crystals under extreme pressures during asteroid impacts on celestial bodies. This paper provides a broad review of the most recent experimental work carried out in this field with a special focus on the methods used. All typical schemes used to produce WDM are discussed in detail. Most of the diagnostic techniques recently established to probe WDM are also described. This paper also provides an overview of the most prominent examples of these methods used in experiments. Even though the main emphasis of the publication is experimental work focused on laboratory astrophysics primarily at laser facilities, a brief outline of other methods such as dynamic compression with z-pinches and static compression using diamond anvil cells (DAC) is also included. Some relevant theoretical and computational efforts related to WDM and astrophysics are mentioned in this review.
High Power Laser Science and Engineering
  • Publication Date: Nov. 29, 2018
  • Vol.6 Issue, 4 04000e59 (2018)
Research Articles
Suppression of amplitude modulation induced by polarization mode dispersion using a multi-degree-of-freedom fiber filter
Rao Li, Youen Jiang, Zhi Qiao, Canhong Huang, Wei Fan, Xuechun Li, and Zunqi Lin
Polarization mode dispersion (PMD) in fibers for high-power lasers can induce significant frequency modulation to amplitude modulation (FM-to-AM) conversion. However, existing techniques are not sufficiently flexible to achieve efficient compensation for such FM-to-AM conversion. By analyzing the nonuniform transmission spectrum caused by PMD, we found that the large-scale envelope of the transmission spectrum has more serious impacts on the amount of AM. In order to suppress the PMD-induced FM-to-AM conversion, we propose a novel tunable spectral filter with multiple degrees of freedom based on a half-wave plate, a nematic liquid crystal, and an axis-rotated polarization-maintaining fiber. Peak wavelength, free spectral range (FSR), and modulation depth of the filter are decoupled and can be controlled independently, which is verified through both simulations and experiments. The filter is utilized to compensate for the PMD-induced FM-to-AM conversion in the front end of a high-power laser facility. The results indicate that, for a pulse with phase-modulation frequency of 22.82 GHz, the FM-to-AM conversion could be reduced from 18% to 3.2% within a short time and maintained below 6.5% for 3 h. The proposed filter is also promising for other applications that require flexible spectral control such as high-speed channel selection in optical communication networks.
High Power Laser Science and Engineering
  • Publication Date: Nov. 11, 2018
  • Vol.6 Issue, 4 04000e53 (2018)
Loss mechanism of all-fiber cascaded side pumping combiner
Chengmin Lei, Zilun Chen, Yanran Gu, Hu Xiao, and Jing Hou
Compared with end pumping fiber combiner, one of the advantages for side pumping combiner is the unlimited pumping points, which means multi-point or cascaded side pumping can be realized. However, the loss mechanism of the cascaded structure is rarely discussed. In this paper, we present the numerical and experimental investigation about the loss mechanism of a two-stage-cascaded side pumping combiner based on tapered-fused technique. The influence of loss mechanism on the coupling efficiency and thermal load of the fiber coating is analyzed according to simulations and experiments with different tapering ratios for the first stage. Based on the analysis, a cascaded component with total pump coupling efficiency of 96.4% handling a pump power of 1088 W is achieved by employing 1018 nm fiber laser as the pump source. Future work to further improve the performance of a cascaded side pumping combiner is discussed and prospected.
High Power Laser Science and Engineering
  • Publication Date: Dec. 27, 2018
  • Vol.6 Issue, 4 04000e56 (2018)
High power all-fiberized and narrow-bandwidth MOPA system by tandem pumping strategy for thermally induced mode instability suppression
Pengfei Ma, Hu Xiao, Daren Meng, Wei Liu, Rumao Tao, Jinyong Leng, Yanxing Ma, Rongtao Su, Pu Zhou, and Zejin Liu
An all-fiberized and narrow-bandwidth master oscillator power amplification (MOPA) system with record output power of 4 kW level and slope efficiency of 78% is demonstrated. Tandem pumping strategy is tentatively introduced into the narrow-bandwidth MOPA system for thermally induced mode instability (TMI) suppression. The stimulated Brillouin scattering (SBS) effect is balanced by simply using one-stage phase modulation technique. With different phase modulation signals, SBS limited output powers of 336 W, 1.2 kW and 3.94 kW are respectively achieved with spectral bandwidths accounting for 90% power of ${\sim}$ 0.025, 0.17 and ${\sim}$ 0.89 nm. Compared with our previous 976 nm pumping system, TMI threshold is overall boosted to be ${>}$ 5 times in which tandem pumping increases the TMI threshold of ${>}$ 3 times. The beam quality ( $M^{2}$ factor) of the output laser is well within 1.5 below the TMI threshold while it is ultimately saturated to be 1.86 with the influence of TMI at maximal output power. Except for SBS and TMI, stimulated Raman scattering (SRS) effect will be another challenge for further power scaling. In such a high power MOPA system, multi-detrimental effects (SBS, SRS and TMI) will coexist and may be mutual-coupled, which could provide a well platform for further comprehensively investigating and optimizing the high power, narrow-bandwidth fiber amplifiers.
High Power Laser Science and Engineering
  • Publication Date: Mar. 21, 2019
  • Vol.6 Issue, 4 04000e57 (2018)
Optimization of the pulse width and injection time in a double-pass laser amplifier
Daewoong Park, Jihoon Jeong, and Tae Jun Yu
High Power Laser Science and Engineering
  • Publication Date: Dec. 27, 2018
  • Vol.6 Issue, 4 04000e60 (2018)
All-optical acceleration in the laser wakefield
F. Zhang, Z. G. Deng, L. Q. Shan, Z. M. Zhang, B. Bi, D. X. Liu, W. W. Wang, Z. Q. Yuan, C. Tian, S. Q. Yang, B. Zhang, and Y. Q. Gu
Muons produced by the Bethe–Heitler process from laser wakefield accelerated electrons interacting with highmaterials have velocities close to the laser wakefield. It is possible to accelerate those muons with laser wakefield directly. Therefore for the first time we propose an all-optical ‘Generator and Booster’ scheme to accelerate the produced muons by another laser wakefield to supply a prompt, compact, low cost and controllable muon source in laser laboratories. The trapping and acceleration of muons are analyzed by one-dimensional analytic model and verified by two-dimensional particle-in-cell (PIC) simulation. It is shown that muons can be trapped in a broad energy range and accelerated to higher energy than that of electrons for longer dephasing length. We further extrapolate the dependence of the maximum acceleration energy of muons with the laser wakefield relativistic factorand the relevant initial energy. It is shown that a maximum energy up to 15.2 GeV is promising withandon the existing short pulse laser facilities.
High Power Laser Science and Engineering
  • Publication Date: Dec. 27, 2018
  • Vol.6 Issue, 4 04000e63 (2018)
Dispersion effects on performance of free-electron laser based on laser wakefield accelerator
Ke Feng, Changhai Yu, Jiansheng Liu, Wentao Wang, Zhijun Zhang, Rong Qi, Ming Fang, Jiaqi Liu, Zhiyong Qin, Ying Wu, Yu Chen, Lintong Ke, Cheng Wang, and Ruxin Li
In this study, we investigate a new simple scheme using a planar undulator (PU) together with a properly dispersed electron beam (beam) with a large energy spread () to enhance the free-electron laser (FEL) gain. For a dispersedbeam in a PU, the resonant condition is satisfied for the center electrons, while the frequency detuning increases for the off-center electrons, inhibiting the growth of the radiation. The PU can act as a filter for selecting the electrons near the beam center to achieve the radiation. Although only the center electrons contribute, the radiation can be enhanced significantly owing to the high-peak current of the beam. Theoretical analysis and simulation results indicate that this method can be used for the improvement of the radiation performance, which has great significance for short-wavelength FEL applications.
High Power Laser Science and Engineering
  • Publication Date: Dec. 27, 2018
  • Vol.6 Issue, 4 04000e64 (2018)

About the Cover

A snapshot of a DFT-MD simulation of isochoricaly heated warm dense beryllium at a temperature of 12 eV. Shown are the position of the nuclei (green spheres) and several isosurfaces of the electronic density ranging from core electrons to valence electrons.