• Special Issue
  • High Energy Density Physics and High Power Lasers 2018
  • 21 Article (s)
Performance demonstration of the PEnELOPE main amplifier HEPA I using broadband nanosecond pulses
D. Albach, M. Loeser, M. Siebold, and U. Schramm
High Power Laser Science and Engineering
  • Publication Date: Dec. 27, 2018
  • Vol.7 Issue, 1 010000e1 (2019)
Reflection of intense laser light from microstructured targets as a potential diagnostic of laser focus and plasma temperature
J. Jarrett, M. King, R. J. Gray, N. Neumann, L. Döhl, C. D. Baird, T. Ebert, M. Hesse, A. Tebartz, D. R. Rusby, N. C. Woolsey, D. Neely, M. Roth, and P. McKenna
The spatial-intensity profile of light reflected during the interaction of an intense laser pulse with a microstructured target is investigated experimentally and the potential to apply this as a diagnostic of the interaction physics is explored numerically. Diffraction and speckle patterns are measured in the specularly reflected light in the cases of targets with regular groove and needle-like structures, respectively, highlighting the potential to use this as a diagnostic of the evolving plasma surface. It is shown, via ray-tracing and numerical modelling, that for a laser focal spot diameter smaller than the periodicity of the target structure, the reflected light patterns can potentially be used to diagnose the degree of plasma expansion, and by extension the local plasma temperature, at the focus of the intense laser light. The reflected patterns could also be used to diagnose the size of the laser focal spot during a high-intensity interaction when using a regular structure with known spacing.
High Power Laser Science and Engineering
  • Publication Date: Dec. 27, 2018
  • Vol.7 Issue, 1 010000e2 (2019)
Dynamic stabilization of plasma instability
S. Kawata, T. Karino, and Y. J. Gu
The paper presents a review of dynamic stabilization mechanisms for plasma instabilities. One of the dynamic stabilization mechanisms for plasma instability was proposed in the paper [Kawata, Phys. Plasmas 19, 024503 (2012)], based on a perturbation phase control. In general, instabilities emerge from the perturbations. Normally the perturbation phase is unknown, and so the instability growth rate is discussed. However, if the perturbation phase is known, the instability growth can be controlled by a superimposition of perturbations imposed actively. Based on this mechanism we present the application results of the dynamic stabilization mechanism to the Rayleigh–Taylor instability (RTI) and to the filamentation instability as typical examples in this paper. On the other hand, in the paper [Boris, Comments Plasma Phys. Control. Fusion 3, 1 (1977)] another mechanism was proposed to stabilize RTI, and was realized by the pulse train or the laser intensity modulation in laser inertial fusion [Betti et al., Phys. Rev. Lett. 71, 3131 (1993)]. In this latter mechanism, an oscillating strong force is applied to modify the basic equation, and consequently the new stabilization window is created. Originally the latter was proposed by Kapitza. We review the two stabilization mechanisms, and present the application results of the former dynamic stabilization mechanism.
High Power Laser Science and Engineering
  • Publication Date: Dec. 27, 2018
  • Vol.7 Issue, 1 010000e3 (2019)
Technology development for ultraintense all-OPCPA systems|Editors' Pick
J. Bromage, S.-W. Bahk, I. A. Begishev, C. Dorrer, M. J. Guardalben, B. N. Hoffman, J. B. Oliver, R. G. Roides, E. M. Schiesser, M. J. Shoup, M. Spilatro, B. Webb, D. Weiner, and J. D. Zuegel
Optical parametric chirped-pulse amplification (OPCPA) [Dubietis et al., Opt. Commun. 88, 437 (1992)] implemented by multikilojoule Nd:glass pump lasers is a promising approach to produce ultraintense pulses (${>}10^{23}~\text{W}/\text{cm}^{2}$). Technologies are being developed to upgrade the OMEGA EP Laser System with the goal to pump an optical parametric amplifier line (EP OPAL) with two of the OMEGA EP beamlines. The resulting ultraintense pulses (1.5 kJ, 20 fs, $10^{24}~\text{W}/\text{cm}^{2}$) would be used jointly with picosecond and nanosecond pulses produced by the other two beamlines. A midscale OPAL pumped by the Multi-Terawatt (MTW) laser is being constructed to produce 7.5-J, 15-fs pulses and demonstrate scalable technologies suitable for the upgrade. MTW OPAL will share a target area with the MTW laser (50 J, 1 to 100 ps), enabling several joint-shot configurations. We report on the status of the MTW OPAL system, and the technology development required for this class of all-OPCPA laser system for ultraintense pulses.
High Power Laser Science and Engineering
  • Publication Date: Feb. 08, 2019
  • Vol.7 Issue, 1 010000e4 (2019)
Study of backward terahertz radiation from intense picosecond laser–solid interactions using a multichannel calorimeter system|On the Cover
H. Liu, G.-Q. Liao, Y.-H. Zhang, B.-J. Zhu, Z. Zhang, Y.-T. Li, G. G. Scott, D. Rusby, C. Armstrong, E. Zemaityte, P. Bradford, N. Woolsey, P. Huggard, P. McKenna, and D. Neely
A multichannel calorimeter system is designed and constructed which is capable of delivering single-shot and broad-band spectral measurement of terahertz (THz) radiation generated in intense laser&ndash;plasma interactions. The generation mechanism of backward THz radiation (BTR) is studied by using the multichannel calorimeter system in an intense picosecond laser&ndash;solid interaction experiment. The dependence of the BTR energy and spectrum on laser energy, target thickness and pre-plasma scale length is obtained. These results indicate that coherent transition radiation is responsible for the low-frequency component (${<}$1 THz) of BTR. It is also observed that a large-scale pre-plasma primarily enhances the high-frequency component (${>}$3 THz) of BTR.
High Power Laser Science and Engineering
  • Publication Date: Jan. 22, 2019
  • Vol.7 Issue, 1 010000e6 (2019)
High-power, Joule-class, temporally shaped multi-pass ring laser amplifier with two Nd:glass laser heads
Jiangtao Guo, Jiangfeng Wang, Hui Wei, Wenfa Huang, Tingrui Huang, Gang Xia, Wei Fan, and Zunqi Lin
A high-power, Joule-class, nanosecond temporally shaped multi-pass ring laser amplifier system with two neodymium-doped phosphate glass (Nd:glass) laser heads is demonstrated. The laser amplifier system consists of three parts: an all-fiber structure seeder, a diode-pumped Nd:glass regenerative amplifier and a multi-pass ring amplifier, where the thermally induced depolarization of two laser heads is studied experimentally and theoretically. Following the injection of a square pulse with the pulse energy of 0.9 mJ and pulse width of 6 ns, a 0.969-J high-energy laser pulse at 1 Hz was generated, which had the ability to change the waveform arbitrarily, based on the all-fiber structure front end. The experimental results show that the proposed laser system is promising to be adopted in the preamplifier of high-power laser facilities.
High Power Laser Science and Engineering
  • Publication Date: Feb. 07, 2019
  • Vol.7 Issue, 1 010000e8 (2019)
High damage threshold liquid crystal binary mask for laser beam shaping
Gang Xia, Wei Fan, Dajie Huang, He Cheng, Jiangtao Guo, and Xiaoqin Wang
In order to improve the damage threshold and enlarge the aperture of a laser beam shaper, photolithographic patterning technology is adopted to design a new type of liquid crystal binary mask. The inherent conductive metal layer of commercial liquid crystal electro-optical spatial light modulators is replaced by azobenzene-based photoalignment layers patterned by noncontact photolithography. Using the azobenzene-based photoalignment layer, a liquid crystal binary mask for beam shaping is fabricated. In addition, the shaping ability, damage threshold, write/erase flexibility and stability of the liquid crystal binary mask are tested. Using a 1 Hz near-IR (1064 nm) laser, the multiple-shot nanosecond damage threshold of the liquid crystal mask is measured to be higher than $15~\text{J}/\text{cm}^{2}$. The damage threshold of the azobenzene-based photoalignment layer is higher than $50~\text{J}/\text{cm}^{2}$ under the same testing conditions.
High Power Laser Science and Engineering
  • Publication Date: Feb. 11, 2019
  • Vol.7 Issue, 1 010000e9 (2019)
Role of magnetic field evolution on filamentary structure formation in intense laser–foil interactions
M. King, N. M. H. Butler, R. Wilson, R. Capdessus, R. J. Gray, H. W. Powell, R. J. Dance, H. Padda, B. Gonzalez-Izquierdo, D. R. Rusby, N. P. Dover, G. S. Hicks, O. C. Ettlinger, C. Scullion, D. C. Carroll, Z. Najmudin, M. Borghesi, D. Neely, and P. McKenna
High Power Laser Science and Engineering
  • Publication Date: Mar. 13, 2019
  • Vol.7 Issue, 1 01000e14 (2019)
High-brightness all-fiber Raman lasers directly pumped by multimode laser diodes
S. A. Babin
High-brightness fiber laser sources usually utilize active rare-earth-doped fibers cladding-pumped by multimode laser diodes (LDs), but they operate in limited wavelength ranges. Singlemode-passive-fiber based Raman lasers are able to operate at almost any wavelength being pumped by high-power fiber lasers. One of the interesting possibilities is to directly pump graded-index (GRIN) multimode passive fibers by available high-power multimode LDs at 915–940 nm, thus achieving high-power Raman lasing in the wavelength range of 950–1000 nm, which is problematic for rare-earth-doped fiber lasers. Here we review the latest results on the development of all-fiber high-brightness LD-pumped sources based on GRIN fiber with in-fiber Bragg gratings (FBGs). The mode-selection properties of FBGs inscribed by fs pulses supported by the Raman clean-up effect result in efficient conversion of multimode pump into a high-quality output beam at 9xx nm. GRIN fibers with core diameters 62.5, 85 and $100~\unicode[STIX]{x03BC}\text{m}$ are compared. Further scaling capabilities and potential applications of such sources are discussed.
High Power Laser Science and Engineering
  • Publication Date: Mar. 13, 2019
  • Vol.7 Issue, 1 01000e15 (2019)
Polarized proton beams from laser-induced plasmas
Anna Hützen, Johannes Thomas, Jürgen Böker, Ralf Engels, Ralf Gebel, Andreas Lehrach, Alexander Pukhov, T. Peter Rakitzis, Dimitris Sofikitis, and Markus Büscher
We report on the concept of an innovative source to produce polarized proton/deuteron beams of a kinetic energy up to several GeV from a laser-driven plasma accelerator. Spin effects have been implemented into the particle-in-cell (PIC) simulation code VLPL (Virtual Laser Plasma Lab) to make theoretical predictions about the behavior of proton spins in laser-induced plasmas. Simulations of spin-polarized targets show that the polarization is conserved during the acceleration process. For the experimental realization, a polarized HCl gas-jet target is under construction using the fundamental wavelength of a Nd:YAG laser system to align the HCl bonds and simultaneously circularly polarized light of the fifth harmonic to photo-dissociate, yielding nuclear polarized H atoms. Subsequently, their degree of polarization is measured with a Lamb-shift polarimeter. The final experiments, aiming at the first observation of a polarized particle beam from laser-generated plasmas, will be carried out at the 10 PW laser system SULF at SIOM, Shanghai.
High Power Laser Science and Engineering
  • Publication Date: Mar. 14, 2019
  • Vol.7 Issue, 1 01000e16 (2019)