Contents
2021
Volume: 9 Issue 2
25 Article(s)

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Special Issue on Target Fabrication
Morphology analysis of tracks in the aerogels impacted by hypervelocity irregular particles
Ai Du, Yi Ma, Mingfang Liu, Zhihua Zhang, Guangwei Cao, Hongwei Li, Ling Wang, Peijian Si, Jun Shen, and Bin Zhou
As an attractive collector medium for hypervelocity particles, combined with outstanding physical properties and suitable compositional characteristics, SiO2 aerogel has been deployed on outer space missions and laser shock-loaded collection experiments. In this paper, impact experiments were conducted to understand the penetration process of irregular grains, irregular Al2O3 grains with two different sizes and speeds (~110 μm@7 km/s, ~251 μm@2.3 km/s) at various density silica aerogels. By classifying the shapes of projectile residues and tracks, the morphology of tracks was analyzed. It was observed that there were several kinds of typical tracks in the penetration of irregular grains, accompanied by residues with the shapes of near-sphere, polyhedron, streamlined body wedge, and rotator. The rotational behavior was demonstrated by the final status of one flake projectile as direct evidence. In addition, there was no obvious relationship between the track length and experimental parameters, which may be caused by the uncertain interaction between aerogels and irregular particles. In addition, it confirmed the existence of fragmentation, melting situation by observing the shape of the impact entrance hole. At the same time, optical coherence tomography was used to observe the detail of tracks clearly, which provided a method to characterize the tracks nondestructively.
High Power Laser Science and Engineering
  • Publication Date: Jan. 01, 1900
  • Vol.9 Issue, 2 02000e14 (2021)
Radial density profile and stability of capillary discharge plasma waveguides of lengths up to 40 cm
M. Turner, A. J. Gonsalves, S. S. Bulanov, C. Benedetti, N. A. Bobrova, V. A. Gasilov, P. V. Sasorov, G. Korn, K. Nakamura, J. van Tilborg, C. G. Geddes, C. B. Schroeder, and E. Esarey
We measured the parameter reproducibility and radial electron density profile of capillary discharge waveguides with diameters of 650 $\mathrm{\mu} \mathrm{m}$ to 2 mm and lengths of 9 to 40 cm. To the best of the authors’ knowledge, 40 cm is the longest discharge capillary plasma waveguide to date. This length is important for $\ge$10 GeV electron energy gain in a single laser-driven plasma wakefield acceleration stage. Evaluation of waveguide parameter variations showed that their focusing strength was stable and reproducible to $% and their average on-axis plasma electron density to $%. These variations explain only a small fraction of laser-driven plasma wakefield acceleration electron bunch variations observed in experiments to date. Measurements of laser pulse centroid oscillations revealed that the radial channel profile rises faster than parabolic and is in excellent agreement with magnetohydrodynamic simulation results. We show that the effects of non-parabolic contributions on Gaussian pulse propagation were negligible when the pulse was approximately matched to the channel. However, they affected pulse propagation for a non-matched configuration in which the waveguide was used as a plasma telescope to change the focused laser pulse spot size.
High Power Laser Science and Engineering
  • Publication Date: Jan. 01, 1900
  • Vol.9 Issue, 2 02000e17 (2021)
Targets with cone-shaped microstructures from various materials for enhanced high-intensity laser–matter interaction | Editors' Pick
Tina Ebert, René Heber, Torsten Abel, Johannes Bieker, Gabriel Schaumann, and Markus Roth
High Power Laser Science and Engineering
  • Publication Date: Jan. 01, 1900
  • Vol.9 Issue, 2 02000e24 (2021)
Fabrication of large-area uniform carbon nanotube foams as near-critical-density targets for laser–plasma experiments
Pengjie Wang, Guijun Qi, Zhuo Pan, Defeng Kong, Yinren Shou, Jianbo Liu, Zhengxuan Cao, Zhusong Mei, Shirui Xu, Zhipeng Liu, Shiyou Chen, Ying Gao, Jiarui Zhao, and Wenjun Ma
Carbon nanotube foams (CNFs) have been successfully used as near-critical-density targets in the laser-driven acceleration of high-energy ions and electrons. Here we report the recent advances in the fabrication technique of such targets. With the further developed floating catalyst chemical vapor deposition (FCCVD) method, large-area ($>25\kern0.5em {\mathrm{cm}}^2$) and highly uniform CNFs are successfully deposited on nanometer-thin metal or plastic foils as double-layer targets. The density and thickness of the CNF can be controlled in the range of $1{-}13\kern0.5em \mathrm{mg}/{\mathrm{cm}}^3$ and $10{-}200\kern0.5em \mu \mathrm{m}$, respectively, by varying the synthesis parameters. The dependence of the target properties on the synthesis parameters and the details of the target characterization methods are presented for the first time.
High Power Laser Science and Engineering
  • Publication Date: Jan. 01, 1900
  • Vol.9 Issue, 2 02000e29 (2021)
Fabrication of disk-shaped, deuterated resorcinol/formaldehyde foam target for laser–plasma experiments
Yumi Kaneyasu, Keiji Nagai, Marilou Cadatal-Raduban, Daniil Golovin, Satoshi Shokita, Akifumi Yogo, Takahisa Jitsuno, Takayoshi Norimatsu, and Kohei Yamanoi
High Power Laser Science and Engineering
  • Publication Date: Jan. 01, 1900
  • Vol.9 Issue, 2 02000e31 (2021)
Deuterated polyethylene nanowire arrays for high-energy density physics
M. G. Capeluto, A. Curtis, C. Calvi, R. Hollinger, V. N. Shlyaptsev, and J. J. Rocca
The interaction of intense, ultrashort laser pulses with ordered nanostructure arrays offers a path to the efficient creation of ultra-high-energy density (UHED) matter and the generation of high-energy particles with compact lasers. Irradiation of deuterated nanowires arrays results in a near-solid density environment with extremely high temperatures and large electromagnetic fields in which deuterons are accelerated to multi-megaelectronvolt energies, resulting in deuterium–deuterium (D–D) fusion. Here we focus on the method of fabrication and the characteristics of ordered arrays of deuterated polyethylene nanowires. The irradiation of these array targets with femtosecond pulses of relativistic intensity and joule-level energy creates a micro-scale fusion environment that produced $2\times {10}^6$ neutrons per joule, an increase of about 500 times with respect to flat solid CD2 targets irradiated with the same laser pulses. Irradiation with 8 J laser pulses was measured to generate up to 1.2 × 107 D–D fusion neutrons per shot.
High Power Laser Science and Engineering
  • Publication Date: Jan. 01, 1900
  • Vol.9 Issue, 2 02000e34 (2021)
Research Articles
Overview and specifications of laser and target areas at the Intense Laser Irradiation Laboratory
Leonida A. Gizzi, Luca Labate, Federica Baffigi, Fernando Brandi, Giancarlo Bussolino, Lorenzo Fulgentini, Petra Köster, and Daniele Palla
We present the main features of the ultrashort, high-intensity laser installation at the Intense Laser Irradiation Laboratory (ILIL) including laser, beam transport and target area specifications. The laboratory was designed to host laser–target interaction experiments of more than 220 TW peak power, in flexible focusing configurations, with ultrarelativistic intensity on the target. Specifications have been established via dedicated optical diagnostic assemblies and commissioning interaction experiments. In this paper we give a summary of laser specifications available to users, including spatial, spectral and temporal contrast features. The layout of the experimental target areas is presented, with attention to the available configurations of laser focusing geometries and diagnostics. Finally, we discuss radiation protection measures and mechanical stability of the laser focal spot on the target.
High Power Laser Science and Engineering
  • Publication Date: Apr. 20, 2021
  • Vol.9 Issue, 2 02000e10 (2021)
Diode-pumped, electro-optically Q-switched, cryogenic Tm:YAG laser operating at 1.88 μm
Jörg Körner, Venkatesan Jambunathan, Fangxin Yue, Jürgen Reiter, Ondřej Slezák, Petr Navrátil, Samuel Paul David, Antonio Lucianetti, Joachim Hein, Tomáš Mocek, and Malte C. Kaluza
High Power Laser Science and Engineering
  • Publication Date: Apr. 02, 2021
  • Vol.9 Issue, 2 02000e11 (2021)
Multi-octave-spanning supercontinuum generation through high-energy laser filaments in YAG and ZnSe pumped by a 2.4 μm femtosecond Cr:ZnSe laser
Sang-Hoon Nam, Garima C. Nagar, Dennis Dempsey, Ondřej Novák, Bonggu Shim, and Kyung-Han Hong
We present experimental and numerical investigations of high-energy mid-infrared filamentation with multi-octave-spanning supercontinuum generation (SCG), pumped by a 2.4 μm, 250 fs Cr:ZnSe chirped-pulse laser amplifier. The SCG is demonstrated in both anomalous and normal dispersion regimes with YAG and polycrystalline ZnSe, respectively. The formation of stable and robust single filaments along with the visible-to-mid-infrared SCG is obtained with a pump energy of up to 100 μJ in a 6-mm-long YAG medium. To the best of the authors’ knowledge, this is the highest-energy multi-octave-spanning SCG from a laser filament in a solid. On the other hand, the SCG and even-harmonic generation based on random quasi-phase matching (RQPM) are simultaneously observed from the single filaments in a 6-mm-long polycrystalline ZnSe medium with a pump energy of up to 15 μJ. The numerical simulations based on unidirectional pulse propagation equation and RQPM show excellent agreement with the measured multi-octave-spanning SCG and even-harmonic generation. They also reveal the temporal structure of mid-infrared filaments, such as soliton-like self-compression in YAG and pulse broadening in ZnSe.
High Power Laser Science and Engineering
  • Publication Date: Apr. 02, 2021
  • Vol.9 Issue, 2 02000e12 (2021)
High-power linear-polarization burst-mode all-fibre laser and generation of frequency-adjustable microwave signal
Xuan He, Bin Zhang, Shuailin Liu, Linyong Yang, Jinmei Yao, Qilin Wu, Yuxin Zhao, Tao Xun, and Jing Hou
Narrowband microwave generation with tuneable frequency is demonstrated by illuminating a photoconductive semiconductor switch (PCSS) with a burst-mode fibre laser. The whole system is composed of a high-power linearly polarized burst-mode pulsed fibre laser and a linear-state PCSS. To obtain a high-performance microwave signal, a desired envelope of burst is necessary and a pulse pre-compensation technique is adopted to avoid envelope distortion induced by the gain-saturation effect. Resulting from the technique, homogenous peak power distribution in each burst is ensured. The maximum energy of the laser burst pulse reaches 200 μJ with a burst duration of 100 ns at the average power of 10 W, corresponding to a peak power of 4 kW. When the PCSS is illuminated by the burst-mode fibre laser, narrowband microwave generation with tuneable frequency (0.80–1.12 GHz) is obtained with a power up to 300 W. To the best of the authors’ knowledge, it is the first demonstration of frequency-tuneable narrowband microwave generation based on a fibre laser. The high-power burst-mode fibre laser reported here has great potential for generating high-power arbitrary microwave signals for a great deal of applicable demands such as smart adaptive radar and intelligent high-power microwave systems.
High Power Laser Science and Engineering
  • Publication Date: Apr. 20, 2021
  • Vol.9 Issue, 2 02000e13 (2021)
Smooth pulse recovery based on hybrid wavelet threshold denoising and first derivative adaptive smoothing filter
Xinlei Qian, Wei Fan, Xinghua Lu, and Xiaochao Wang
Based on the pulse-shaping unit in the front end of high-power laser facilities, we propose a new hybrid scheme in a closed-loop control system including wavelet threshold denoising for pretreatment and a first derivative adaptive smoothing filter for smooth pulse recovery, so as to effectively restrain the influence of electrical noise and FM-to-AM modulation in the time–power curve, and enhance the calibration accuracy of the pulse shape in the feedback control system. The related simulation and experiment results show that the proposed scheme can obtain a better shaping effect on the high-contrast temporal shape in comparison with the cumulative average algorithm and orthogonal matching pursuit algorithm combined with a traditional smoothing filter. The implementation of the hybrid scheme mechanism increased the signal-to-noise ratio of the laser pulse from about 11 dB to 30 dB, and the filtered pulse is smooth without modulation, with smoothness of about 98.8%.
High Power Laser Science and Engineering
  • Publication Date: Apr. 28, 2021
  • Vol.9 Issue, 2 02000e15 (2021)
Innovative single-shot 2D pulse front tilt diagnostic
M. Galimberti, F. G. Bisesto, and M. Galletti
The presence of pulse front tilt (PFT), caused by angular dispersion (AD) in femtosecond laser pulses, could degrade the performance of the laser system and/or impact the experimental yields. We present a single-shot diagnostic capable of measuring the AD in the x–y plane by adopting an intensity mask. It can be applied to stretched pulses, making it ideal for diagnosing the AD along the amplification chain of a high-power laser system, and to ultrashort pulses exiting from an optical compressor. In this way, it can help in properly characterizing a laser pulse before it is delivered to the target area. In this Letter, we present experimental evidence of AD retrieval for different compression configurations, supported by theoretical analysis.
High Power Laser Science and Engineering
  • Publication Date: Apr. 29, 2021
  • Vol.9 Issue, 2 02000e16 (2021)
A history of high-power laser research and development in the United Kingdom | On the Cover
Colin N. Danson, Malcolm White, John R. M. Barr, Thomas Bett, Peter Blyth, David Bowley, Ceri Brenner, Robert J. Collins, Neal Croxford, A. E. Bucker Dangor, Laurence Devereux, Peter E. Dyer, Anthony Dymoke-Bradshaw, Christopher B. Edwards, Paul Ewart, Allister I. Ferguson, John M. Girkin, Denis R. Hall, David C. Hanna, Wayne Harris, David I. Hillier, Christopher J. Hooker, Simon M. Hooker, Nicholas Hopps, Janet Hull, David Hunt, Dino A. Jaroszynski, Mark Kempenaars, Helmut Kessler, Sir Peter L. Knight, Steve Knight, Adrian Knowles, Ciaran L. S. Lewis, Ken S. Lipton, Abby Littlechild, John Littlechild, Peter Maggs, Graeme P. A. Malcolm, Stuart P. D. Mangles, William Martin, Paul McKenna, Richard O. Moore, Clive Morrison, Zulfikar Najmudin, David Neely, Geoff H. C. New, Michael J. Norman, Ted Paine, Anthony W. Parker, Rory R. Penman, Geoff J. Pert, Chris Pietraszewski, Andrew Randewich, Nadeem H. Rizvi, Nigel Seddon, Zheng-Ming Sheng, David Slater, Roland A. Smith, Christopher Spindloe, Roy Taylor, Gary Thomas, John W. G. Tisch, Justin S. Wark, Colin Webb, S. Mark Wiggins, Dave Willford, and Trevor Winstone
High Power Laser Science and Engineering
  • Publication Date: Apr. 28, 2021
  • Vol.9 Issue, 2 02000e18 (2021)
A novel laser shock post-processing technique on the laser-induced damage resistance of 1ω HfO2/SiO2 multilayer coatings
Tangyang Pu, Wenwen Liu, Yueliang Wang, Xiaoming Pan, Leiqing Chen, and Xiaofeng Liu
The laser shock processing implemented by a laser-induced high-pressure plasma which propagates into the sample as a shockwave is innovatively applied as a post-processing technique on HfO2/SiO2 multilayer coatings for the first time. The pure mechanical post-processing has provided evidence of a considerable promotion effect of the laser-induced damage threshold, which increased by a factor of about 4.6 with appropriate processing parameters. The promotion mechanism is confirmed to be the comprehensive modification of the intrinsic defects and the mechanical properties, which made the applicability of this novel post-processing technique on various types of coatings possible. Based on experiments, an interaction equation for the plasma pressure is established, which clarifies the existence of the critical pressure and provides a theoretical basis for selecting optimal processing parameters. In addition to the further clarification of the underlying damage mechanism, the laser shock post-processing provides a promising technique to realize the comprehensive and effective improvement of the laser-induced damage resistance of coatings.
High Power Laser Science and Engineering
  • Publication Date: May. 18, 2021
  • Vol.9 Issue, 2 02000e19 (2021)
Effective suppression of mode distortion induced by stimulated Raman scattering in high-power fiber amplifiers
Wei Gao, Wenhui Fan, Pei Ju, Gang Li, Yanpeng Zhang, Aifeng He, Qi Gao, and Zhe Li
Mode distortion induced by stimulated Raman scattering (SRS) has become a new obstacle for the further development of high-power fiber lasers with high beam quality. Here, an approach for effective suppression of the SRS-induced mode distortion in high-power fiber amplifiers has been demonstrated experimentally by adjusting the seed power (output power of seed source) and forward feedback coefficient of the rear port in the seed source. It is shown that the threshold power of the SRS-induced mode distortion can be increased significantly by reducing the seed power or the forward feedback coefficient. Moreover, it has also been found that the threshold power is extremely sensitive to the forward feedback power value from the rear port. The influence of the seed power on the threshold power can be attributed to the fact that the seed power plays an important role in the effective length of the gain fiber in the amplifier. The influence of the forward feedback coefficient on the threshold power can be attributed to the enhanced SRS configuration because the end surface of the rear port together with the fiber in the amplifier constitutes a half-opening cavity. This suppression approach will be very helpful to further develop the high-power fiber amplifiers with high beam quality.
High Power Laser Science and Engineering
  • Publication Date: May. 18, 2021
  • Vol.9 Issue, 2 02000e20 (2021)
Novel constant-cladding tapered-core ytterbium-doped fiber for high-power fiber laser oscillator
Yun Ye, Xianfeng Lin, Xiaoming Xi, Chen Shi, Baolai Yang, Hanwei Zhang, Xiaolin Wang, Jinyan Li, and Xiaojun Xu
Power scaling based on traditional ytterbium-doped fibers (YDFs) is limited by optical nonlinear effects and transverse mode instability (TMI) in high-power fiber lasers. Here, we propose a novel long tapered fiber with a constant cladding and tapered core (CCTC) along its axis direction. The tapered-core region of the fiber is designed to enhance the stimulated Raman scattering (SRS) threshold and suppress higher-order mode resonance in the laser cavity. The CCTC YDF was fabricated successfully with a modified chemical vapor deposition (MCVD) method combined with solution doping technology, which has a cladding diameter of 400 μm and a varying core with a diameter of ~24 μm at both ends and ~31 μm in the middle. To test the performance of the CCTC fiber during high-power operation, an all-fiber laser oscillator based on a CCTC YDF was investigated experimentally. As a result, a maximum output power of 3.42 kW was achieved with an optical-to-optical efficiency of 55.2%, although the TMI effect was observed at an output power of ~3.12 kW. The measured beam quality (M2 factor) was ~1.7, and no sign of the Raman component was observed in the spectrum. We believe that CCTC YDF has great potential to simultaneously mitigate the SRS and TMI effects, and further power scaling is promising by optimizing the structure of the YDF.
High Power Laser Science and Engineering
  • Publication Date: May. 18, 2021
  • Vol.9 Issue, 2 02000e21 (2021)
1178 J, 527 nm near diffraction limited laser based on a complete closed-loop adaptive optics controlled off-axis multi-pass amplification laser system
Deen Wang, Xin Zhang, Wanjun Dai, Ying Yang, Xuewei Deng, Lin Chen, Xudong Xie, Dongxia Hu, Feng Jing, Zeping Yang, Qiang Yuan, Xiaofeng Wei, Qihua Zhu, Wanguo Zheng, Xiaomin Zhang, and Lei Huang
A 1178 J near diffraction limited 527 nm laser is realized in a complete closed-loop adaptive optics (AO) controlled off-axis multi-pass amplification laser system. Generated from a fiber laser and amplified by the pre-amplifier and the main amplifier, a 1053 nm laser beam with the energy of 1900 J is obtained and converted into a 527 nm laser beam by a KDP crystal with 62% conversion efficiency, 1178 J and beam quality of 7.93 times the diffraction limit (DL). By using a complete closed-loop AO configuration, the static and dynamic wavefront distortions of the laser system are measured and compensated. After correction, the diameter of the circle enclosing 80% energy is improved remarkably from 7.93DL to 1.29DL. The focal spot is highly concentrated and the 1178 J, 527 nm near diffraction limited laser is achieved.
High Power Laser Science and Engineering
  • Publication Date: May. 24, 2021
  • Vol.9 Issue, 2 02000e22 (2021)
Design of large mode area all-solid anti-resonant fiber for high-power lasers
Xin Zhang, Shoufei Gao, Yingying Wang, Wei Ding, and Pu Wang
High-power fiber lasers have experienced a dramatic development over the last decade. Further increasing the output power needs an upscaling of the fiber mode area, while maintaining a single-mode output. Here, we propose an all-solid anti-resonant fiber (ARF) structure, which ensures single-mode operation in broadband by resonantly coupling higher-order modes into the cladding. A series of fibers with core sizes ranging from 40 to 100 μm are proposed exhibiting maximum mode area exceeding 5000 μm2. Numerical simulations show this resonant coupling scheme provides a higher-order mode (mainly TE01, TM01, and HE21) suppression ratio of more than 20 dB, while keeping the fundamental mode loss lower than 1 dB/m. The proposed structure also exhibits high tolerance for core index depression.
High Power Laser Science and Engineering
  • Publication Date: May. 24, 2021
  • Vol.9 Issue, 2 02000e23 (2021)
High-power non-perturbative laser delivery diagnostics at the final focus of 100-TW-class laser pulses
Fumika Isono, Jeroen van Tilborg, Samuel K. Barber, Joseph Natal, Curtis Berger, Hai-En Tsai, Tobias Ostermayr, Anthony Gonsalves, Cameron Geddes, and Eric Esarey
Controlling the delivery of multi-terawatt and petawatt laser pulses to final focus, both in position and angle, is critical to many laser applications such as optical guiding, laser–plasma acceleration, and laser-produced secondary radiation. We present an online, non-destructive laser diagnostic, capable of measuring the transverse position and pointing angle at focus. The diagnostic is based on a unique double-surface-coated wedged-mirror design for the final steering optic in the laser line, producing a witness beam highly correlated with the main beam. By propagating low-power kilohertz pulses to focus, we observed spectra of focus position and pointing angle fluctuations dominated by frequencies below 70 Hz. The setup was also used to characterize the excellent position and pointing angle correlation of the 1 Hz high-power laser pulses to this low-power kilohertz pulse train, opening a promising path to fast non-perturbative feedback concepts even on few-hertz-class high-power laser systems.
High Power Laser Science and Engineering
  • Publication Date: Aug. 03, 2021
  • Vol.9 Issue, 2 02000e25 (2021)
Modeling of three-dimensional exciplex pumped fluid Cs vapor laser with transverse and longitudinal gas flow
Chenyi Su, Xingqi Xu, Jinghua Huang, and Bailiang Pan
Considering the thermodynamical fluid mechanics in the gain medium and laser kinetic processes, a three-dimensional theoretical model of an exciplex-pumped Cs vapor laser with longitudinal and transverse gas flow is established. The slope efficiency of laser calculated by the model shows good agreement with the experimental data. The comprehensive three-dimensional distribution of temperature and particle density of Cs is depicted. The influence of pump intensity, wall temperature, and fluid velocity on the laser output performance is also simulated and analyzed in detail, suggesting that a higher wall temperature can guarantee a higher output laser power while causing a more significant heat accumulation in the cell. Compared with longitudinal gas flow, the transverse flow can improve the output laser power by effectively removing the generated heat accumulation and alleviating the temperature gradient in the cell.
High Power Laser Science and Engineering
  • Publication Date: Jun. 10, 2021
  • Vol.9 Issue, 2 02000e26 (2021)
First radiative shock experiments on the SG-II laser
Francisco Suzuki-Vidal, Thomas Clayson, Chantal Stehlé, Uddhab Chaulagain, Jack W. D. Halliday, Mingying Sun, Lei Ren, Ning Kang, Huiya Liu, Baoqiang Zhu, Jianqiang Zhu, Carolina De Almeida Rossi, Teodora Mihailescu, Pedro Velarde, Manuel Cotelo, John M. Foster, Colin N. Danson, Christopher Spindloe, Jeremy P. Chittenden, and Carolyn Kuranz
We report on the design and first results from experiments looking at the formation of radiative shocks on the Shenguang-II (SG-II) laser at the Shanghai Institute of Optics and Fine Mechanics in China. Laser-heating of a two-layer CH/CH–Br foil drives a $\sim 40$ km/s shock inside a gas cell filled with argon at an initial pressure of 1 bar. The use of gas-cell targets with large (several millimetres) lateral and axial extent allows the shock to propagate freely without any wall interactions, and permits a large field of view to image single and colliding counter-propagating shocks with time-resolved, point-projection X-ray backlighting ($\sim 20$ μm source size, 4.3 keV photon energy). Single shocks were imaged up to 100 ns after the onset of the laser drive, allowing to probe the growth of spatial nonuniformities in the shock apex. These results are compared with experiments looking at counter-propagating shocks, showing a symmetric drive that leads to a collision and stagnation from $\sim 40$ ns onward. We present a preliminary comparison with numerical simulations with the radiation hydrodynamics code ARWEN, which provides expected plasma parameters for the design of future experiments in this facility.
High Power Laser Science and Engineering
  • Publication Date: Jun. 10, 2021
  • Vol.9 Issue, 2 02000e27 (2021)
New phase-matching selection rule to generate angularly isolated harmonics
Xiaomei Zhang, Baifei Shen, Lingang Zhang, and Yin Shi
High harmonic generation (HHG) is an ideal probing source. In general, all harmonics are coupled with the corresponding input laser when generated, and for applications, they are separated using additional spectrometers. Herein, we report the angular isolation of relativistic harmonics at a predicted emission angle upon generation and, most importantly, a new phase-matching chain selection rule is derived to generate harmonics. Based on the laser plasma mechanism involving two non-collinear relativistic driving lasers, the nth harmonic carrying the information of both input lasers originates from its adjacent (n – 1)th harmonic coupled with one of the input lasers. Meanwhile, the intensity and emission angle of the generated isolated harmonic are both greatly increased compared with those in the gas scheme. These results are satisfactorily verified by theoretical analysis and three-dimensional particle-in-cell simulations, which have physical significance and are essential for practical applications.
High Power Laser Science and Engineering
  • Publication Date: Jun. 16, 2021
  • Vol.9 Issue, 2 02000e28 (2021)
Design, installation and commissioning of the ELI-Beamlines high-power, high-repetition rate HAPLS laser beam transport system to P3
S. Borneis, T. Laštovička, M. Sokol, T.-M. Jeong, F. Condamine, O. Renner, V. Tikhonchuk, H. Bohlin, A. Fajstavr, J.-C. Hernandez, N. Jourdain, D. Kumar, D. Modřanský, A. Pokorný, A. Wolf, S. Zhai, G. Korn, and S. Weber
The design and the early commissioning of the ELI-Beamlines laser facility’s 30 J, 30 fs, 10 Hz HAPLS (High-repetition-rate Advanced Petawatt Laser System) beam transport (BT) system to the P3 target chamber are described in detail. It is the world’s first and with 54 m length, the longest distance high average power petawatt (PW) BT system ever built. It connects the HAPLS pulse compressor via the injector periscope with the 4.5 m diameter P3 target chamber of the plasma physics group in hall E3. It is the largest target chamber of the facility and was connected first to the BT system. The major engineering challenges are the required high vibration stability mirror support structures, the high pointing stability optomechanics as well as the required levels for chemical and particle cleanliness of the vacuum vessels to preserve the high laser damage threshold of the dielectrically coated high-power mirrors. A first commissioning experiment at low pulse energy shows the full functionality of the BT system to P3 and the novel experimental infrastructure.
High Power Laser Science and Engineering
  • Publication Date: Aug. 03, 2021
  • Vol.9 Issue, 2 02000e30 (2021)
Amplification characteristics in active tapered segmented cladding fiber with large mode area
Caijian Xie, Tigang Ning, Jingjing Zheng, Li Pei, Jianshuai Wang, Jing Li, Haidong You, Chuangye Wang, and Xuekai Gao
A kind of tapered segmented cladding fiber (T-SCF) with large mode area (LMA) is proposed, and the mode and amplification characteristics of T-SCFs with concave, linear, and convex tapered structures are investigated based on finite-element method (FEM) and few-mode steady-state rate equation. Simulation results indicate that the concave tapered structure can introduce high loss for high-order modes (HOMs) that is advantageous to achieve single-mode operation, whereas the convex tapered structure provides large effective mode area that can help to mitigate nonlinear effects. Meanwhile, the small-to-large amplification scheme shows further advantages on stripping off HOMs, and the large-to-small amplification scheme decreases the heat load density induced by the high-power pump. Moreover, single-mode propagation performance, effective mode area, and heat load density of the T-SCF are superior to those of tapered step index fiber (T-SIF). These theoretical model and numerical results can provide instructive suggestions for designing high-power fiber lasers and amplifiers.
High Power Laser Science and Engineering
  • Publication Date: Jun. 22, 2021
  • Vol.9 Issue, 2 02000e32 (2021)
Diode-pumped 10 W femtosecond Yb:CALGO laser with high beam quality
Jinfang Yang, Zhaohua Wang, Jiajun Song, Renchong Lv, Xianzhi Wang, Jiangfeng Zhu, and Zhiyi Wei
High Power Laser Science and Engineering
  • Publication Date: Jun. 25, 2021
  • Vol.9 Issue, 2 02000e33 (2021)