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High Power Laser Science and Engineering 第7卷 第4期

Author Affiliations
Abstract

The original article contained a spelling error in the first author’s name. The correct name is shown here.

High Power Laser Science and Engineering
2019, 7(4): 04000e57
Q. S. Feng 1L. H. Cao 1,2,3Z. J. Liu 1,2C. Y. Zheng 1,2,3,†X. T. He 1,2,3
Author Affiliations
Abstract
1 Institute of Applied Physics and Computational Mathematics, Beijing 100094, China
2 HEDPS, Center for Applied Physics and Technology, Peking University, Beijing 100871, China
3 Collaborative Innovation Center of IFSA (CICIFSA), Shanghai Jiao Tong University, Shanghai 200240, China
The strong-coupling mode, called the “quasimode”, is excited by stimulated Brillouin scattering (SBS) in high-intensity laser–plasma interactions. Also SBS of the quasimode competes with SBS of the fast mode (or slow mode) in multi-ion species plasmas, thus leading to a low-frequency burst behavior of SBS reflectivity. Competition between the quasimode and the ion-acoustic wave (IAW) is an important saturation mechanism of SBS in high-intensity laser–plasma interactions. These results give a clear explanation of the low-frequency periodic burst behavior of SBS and should be considered as a saturation mechanism of SBS in high-intensity laser–plasma interactions.
Brillouin amplification inertial confinement fusion ion-acoustic waves quasimode stimulated Brillouin scattering 
High Power Laser Science and Engineering
2019, 7(4): 04000e58
Tianyue Hou 1Yi An 1Qi Chang 1Pengfei Ma 1,†[ ... ]Pu Zhou 1,†
Author Affiliations
Abstract
1 College of Advanced Interdisciplinary Studies, National University of Defense Technology, Changsha 410073, China
2 Hypervelocity Aerodynamics Institute, China Aerodynamics Research and Development Center, Mianyang 621000, China
We incorporate deep learning (DL) into tiled aperture coherent beam combining (CBC) systems for the first time, to the best of our knowledge. By using a well-trained convolutional neural network DL model, which has been constructed at a non-focal-plane to avoid the data collision problem, the relative phase of each beamlet could be accurately estimated, and then the phase error in the CBC system could be compensated directly by a servo phase control system. The feasibility and extensibility of the phase control method have been demonstrated by simulating the coherent combining of different hexagonal arrays. This DL-based phase control method offers a new way of eliminating dynamic phase noise in tiled aperture CBC systems, and it could provide a valuable reference on alleviating the long-standing problem that the phase control bandwidth decreases as the number of array elements increases.
coherent beam combining deep learning phase control 
High Power Laser Science and Engineering
2019, 7(4): 04000e59
Author Affiliations
Abstract
1 Centro de Laseres Pulsados, Building M5, Science Park, Calle Adaja 8, 37185 Villamayor, Salamanca, Spain
2 Universidad de Salamanca, Patio de Escuelas 1, 37008 Salamanca, Spain
3 CMAM, Universidad Autónoma de Madrid, Campus de Cantoblanco, E-28049 Madrid, Spain
4 Grupo de Electrónica y Semiconductores, Departamento de Física Aplicada, Universidad Autónoma de Madrid, Cantoblanco, E-28049 Madrid, Spain
5 University of Alberta, 116 St85 Ave, Edmonton, AB T6G 2R3, Alberta, Canada
6 Laser-Plasma Chair at the University of Salamanca, Patio de Escuelas 1, Salamanca, Spain
We present a scintillator-based detector able to measure the proton energy and the spatial distribution with a relatively simple design. It has been designed and built at the Spanish Center for Pulsed Lasers (CLPU) in Salamanca and tested in the proton accelerator at the Centro de Micro-Análisis de Materiales (CMAM) in Madrid. The detector is capable of being set in the high repetition rate (HRR) mode and reproduces the performance of the radiochromic film detector. It represents a new class of online detectors for laser–plasma physics experiments in the newly emerging high power laser laboratories working at HRR.
high repetition rate laser particle acceleration online detector proton diagnostic scintillator 
High Power Laser Science and Engineering
2019, 7(4): 04000e60
Author Affiliations
Abstract
1 Key Laboratory for Laser Plasmas (Ministry of Education), Collaborative Innovation Centre of IFSA (CICIFSA), School of Physics and Astronomy, Shanghai Jiao Tong University, Shanghai 200240, China
2 Tsung-Dao Lee Institute, Shanghai Jiao Tong University, Shanghai 200240, China
High-power femtosecond lasers beyond $5~\unicode[STIX]{x03BC}\text{m}$ are attractive for strong-field physics with mid-infrared (IR) fields but are difficult to scale up. In optical parametric chirped-pulse amplification (OPCPA) at mid-IR wavelengths, a nonlinear crystal is vital, and its transmittance, dispersion, nonlinear coefficient and size determine the achievable power and wavelength. OPCPA beyond $5~\unicode[STIX]{x03BC}\text{m}$ routinely relies on semiconductor crystals because common oxide crystals are not transparent in this spectral range. However, the small size and low damage threshold of semiconductor crystals fundamentally limit the peak power to gigawatts. In this paper, we design a terawatt-class OPCPA system at $5.2~\unicode[STIX]{x03BC}\text{m}$ based on a new kind of oxide crystal of $\text{La}_{3}\text{Ga}_{5.5}\text{Nb}_{0.5}\text{O}_{14}$ (LGN). The extended transparent range, high damage threshold, superior phase-matching characteristics and large size of LGN enable the generation of 0.13 TW seven-cycle pulses at $5.2~\unicode[STIX]{x03BC}\text{m}$. This design fully relies on the state-of-the-art OPCPA technology of an octave-spanning ultrafast Ti:sapphire laser and a thin-disk Yb:YAG laser, offering the performance characteristics of high power, a high repetition rate and a stable carrier–envelope phase.
few-cycle mid-infrared OPCPA oxide LGN crystals 
High Power Laser Science and Engineering
2019, 7(4): 04000e61
Author Affiliations
Abstract
1 GSI Helmholtzzentrum für Schwerionenforschung GmbH, Planckstrasse 1, 64291Darmstadt, Germany
2 Helmholtz Institute Jena, Fröbelstieg 3, 07743Jena, Germany
We propose and demonstrate the use of random phase plates (RPPs) for high-energy sub-picosecond lasers. Contrarily to previous work related to nanosecond lasers, an RPP poses technical challenges with ultrashort-pulse lasers. Here, we implement the RPP near the beginning of the amplifier and image-relay it throughout the laser amplifier. With this, we obtain a uniform intensity distribution in the focus over an area 1600 times the diffraction limit. This method shows no significant drawbacks for the laser and it has been implemented at the PHELIX laser facility where it is now available for users.
beam shaping high-power laser phase plate short-pulse laser 
High Power Laser Science and Engineering
2019, 7(4): 04000e62
Author Affiliations
Abstract
546 Carolina Meadows Villa, Chapel Hill, North Carolina27517, USA
Direct-drive laser fusion has one potential advantage over all other approaches to fusion energy. The hot plasma can be kept near or below the various plasma instability thresholds, if one uses purely spherical targets, with a short wavelength, large bandwidth and optically smoothed excimer laser. Instead of trying to manage laser–plasma instabilities, one avoids them. There is a path to complete the evaluation and development of this energy option, with moderate costs and a moderate time scale. Glass lasers, with their longer wavelength and narrower bandwidth, are no longer useful to evaluate fusion targets.
excimer laser laser fusion 
High Power Laser Science and Engineering
2019, 7(4): 04000e63
Author Affiliations
Abstract
1 School of Physics and Optoelectronic Engineering, Xidian University, Xi’an 710071, China
2 Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China
3 Jiangsu Key Laboratory of Advanced Laser Materials and Devices, School of Physics and Electronic Engineering, Jiangsu Normal University, Xuzhou 221116, China
4 School of Physics Science and Engineering, Tongji University, Shanghai 200092, China
We report on the study of single-mode fiber-laser-pumped mode-locked Yb:CALYO lasers via using a passive saturable absorber and Kerr-lens mode-locking technique, respectively. Up to 3.1-W average power with 103-fs pulse duration is obtained from the passive mode-locking, and down to 36-fs pulse duration with more than 2-W average power is achieved by the pure Kerr-lens mode-locking, which is to the best of our knowledge, the highest average power from a reported sub-40-fs Yb-based solid-state oscillator.
fiber pump high power solid-state laser sub-40-fs Yb:CALYO 
High Power Laser Science and Engineering
2019, 7(4): 04000e64
Author Affiliations
Abstract
1 Laboratory of Infrared Material and Devices, Research Institute of Advanced Technologies, Ningbo University, Ningbo315211, China
2 Key Laboratory of Photoelectric Detection Materials and Devices of Zhejiang Province, Ningbo315211, China
3 Faculty of Electrical Engineering and Computer Science, Ningbo University, Ningbo315211, China
We report on the investigation of intermode beating mode-locked (IBML) pulse generation in a simple all-fiber Tm$^{3+}$-doped double clad fiber laser (TDFL). This IBML TDFL is implemented by matching longitudinal-mode frequency between 793 nm laser and TDFL without extra mode locker. The central wavelength of ${\sim}1983~\text{nm}$, the fundamental pulse frequency of ${\sim}9.6~\text{MHz}$ and the signal-to-noise ratio (SNR) of ${>}50~\text{dB}$ are achieved in this IBML TDFL. With laser cavity optimization, the IBML TDFL can finally generate an average output power of 1.03 W with corresponding pulse energy of ${\sim}107~\text{nJ}$. These results can provide an easily accessible way to develop compact large-energy, high-power TDFLs.
average output power intermode beating mode-locking Tm3+ -doped double clad fiber laser pulse energy 
High Power Laser Science and Engineering
2019, 7(4): 04000e65
Author Affiliations
Abstract
1 Institute of Computer Application, China Academy of Engineering Physics, Mianyang621900, China
2 Research Center of Laser Fusion, China Academy of Engineering Physics, Mianyang621900, China
A number of vision-based methods for detecting laser-induced defects on optical components have been implemented to replace the time-consuming manual inspection. While deep-learning-based methods have achieved state-of-the-art performances in many visual recognition tasks, their success often hinges on the availability of a large number of labeled training sets. In this paper, we propose a surface defect detection method based on image segmentation with a U-shaped convolutional network (U-Net). The designed network was trained on paired sets of online and offline images of optics from a large laser facility. We show in our experimental evaluation that our approach can accurately locate laser-induced defects on the optics in real time. The main advantage of the proposed method is that the network can be trained end to end on small samples, without the requirement for manual labeling or manual feature extraction. The approach can be applied to the daily inspection and maintenance of optical components in large laser facilities.
deep learning defect detection laser-induced defects 
High Power Laser Science and Engineering
2019, 7(4): 04000e66
Cheng Xi 1,2,3Peng Wang 1,2,3Xiao Li 1,2,3,†Zejin Liu 1,2,3,†
Author Affiliations
Abstract
1 College of Advanced Interdisciplinary Studies, National University of Defense Technology, Changsha410073, China
2 State Key Laboratory of Pulsed Power Laser Technology, Changsha410073, China
3 Hunan Provincial Key Laboratory of High Energy Laser Technology, Changsha410073, China
We report on a new scheme for efficient continuous-wave (CW) mid-infrared generation using difference frequency generation (DFG) inside a periodically poled lithium niobate (PPLN)-based optical parametric oscillator (OPO). The pump sources were two CW fiber lasers fixed at 1018 nm and 1080 nm. One worked as the assisted laser to build parametric oscillation and generate an oscillating signal beam while the other worked at low power (${\leqslant}3~\text{W}$) to induce DFG between it and the signal beam. The PPLN temperature was appropriately adjusted to enable OPO and DFG to synchronously meet phase-matching conditions. Finally, both low-power 1018 nm and 1080 nm pump beams were successfully converted to $3.1~\unicode[STIX]{x03BC}\text{m}$ and $3.7~\unicode[STIX]{x03BC}\text{m}$ idler beams, respectively. The conversion efficiencies of the 1018 nm and 1080 nm pumped DFG reached 20% and 15%, respectively, while their slope efficiencies reached 19.6% and 15%. All these data were comparable to the OPOs pumped by themselves and never realized before in traditional CW DFG schemes. The results reveal that high-efficiency frequency down-conversion can be achieved with a low-power near-infrared pump source.
difference frequency generation nonlinear wave mixing optical parametric oscillator 
High Power Laser Science and Engineering
2019, 7(4): 04000e67