In the 2015 review paper ‘Petawatt Class Lasers Worldwide’ a comprehensive overview of the current status of high-power facilities of ${>}200~\text{TW}$ was presented. This was largely based on facility specifications, with some description of their uses, for instance in fundamental ultra-high-intensity interactions, secondary source generation, and inertial confinement fusion (ICF). With the 2018 Nobel Prize in Physics being awarded to Professors Donna Strickland and Gerard Mourou for the development of the technique of chirped pulse amplification (CPA), which made these lasers possible, we celebrate by providing a comprehensive update of the current status of ultra-high-power lasers and demonstrate how the technology has developed. We are now in the era of multi-petawatt facilities coming online, with 100 PW lasers being proposed and even under construction. In addition to this there is a pull towards development of industrial and multi-disciplinary applications, which demands much higher repetition rates, delivering high-average powers with higher efficiencies and the use of alternative wavelengths: mid-IR facilities. So apart from a comprehensive update of the current global status, we want to look at what technologies are to be deployed to get to these new regimes, and some of the critical issues facing their development.

Leakage currents and dielectric breakdown were studied in MIS capacitors of metal-aluminum oxide-silicon. The aluminum oxide was produced by thermally oxidizing AlN at 800-1100 C under dry O 2 conditions. The AlN films were deposited by RF magnetron sputtering on p-type Si (100) substrates. Thermal oxidation produced Al 2 O 3 with a thickness and structure that depended on the process time and temperature. The MIS capacitors exhibited the charge regimes of accumulation, depletion, and inversion on the Si semiconductor surface. The best electrical properties were obtained when all of the AlN was fully oxidized to Al 2 O 3 with no residual AlN. The MIS flatband voltage was near 0 V, the net oxide trapped charge density, ox , was less than 10 11 cm 2 , and the interface trap density, , was less than 10 11 cm 2 eV 1 . At an oxide electric field of 0.3 MV/cm, the leakage current density was less than 10 7 A cm 2 , with a resistivity greater than 10 12 -cm. The critical field for dielectric breakdown ranged from 4 to 5 MV/cm. The temperature dependence of the current versus electric field indicated that the conduction mechanism was Frenkel-Poole emission, which has the interesting property that higher temperatures reduce the current. This may be important for the reliability of circuits operating under extreme conditions. The dielectric constant ranged from 3 to 9. The excellent electronic quality of aluminum oxide may be attractive for field effect transistor applications.

We report on the first successful proof-of-principle experiment to manipulate laser-matter interactions on microscales using highly ordered Si microwire arrays. The interaction of a high-contrast short-pulse laser with a flat target via periodic Si microwires yields a substantial enhancement in both the total and cutoff energies of the produced electron beam. The self-generated electric and magnetic fields behave as an electromagnetic lens that confines and guides electrons between the microwires as they acquire relativistic energies via direct laser acceleration. DOI: 10.1103/PhysRevLett.116.085002 Laser-matter interactions at relativistic intensities have exhibited many interesting physical processes. These include the acceleration of electrons [1][2][3][4], protons, and heavy ions [5][6][7], the creation of electron-positron jets [8][9][10], and attosecond pulse generation [11,12]. The investigation of ultrashort pulse lasers interacting with initially soliddensity matter has been mainly focused on flat targets, with little or no control over the interaction. Recently the focus has shifted toward using advanced targets with the aim of increasing laser beam absorption and subsequent energy partition among various plasma species. Structured interfaces including nanoparticles [13], snowflakes [14], and nanospheres [15] have been reported to enhance laser absorption and proton acceleration, and the trapping of femtosecond laser pulses of relativistic intensity deep within ordered nanowires resulted in volumetric heating of dense matter into a new ultrahot plasma regime [16]. Another proposal addressed the potential for prescribing geometrical structures on the front of a target to greatly enhance the yield of high-energy electrons while simultaneously confining the emission to narrow angular cones [17].Microengineering laser plasma interactions, at intensities above the material damage threshold, has not been extensively explored. The main reason is that the amplified short pulses are inherently preceded by nanosecond-scale pedestals [18]. This departure from an ideal pulse can substantially modify or destroy any guiding features before the arrival of the intense portion of the pulse.Laser-pulse cleaning techniques are now being employed to significantly minimize unwanted prepulse and pedestals. For example, Ti:sapphire-based short-pulse high-intensity lasers routinely use a cross-polarized wave generation technique to achieve a contrast of at least 10 10 on the nanosecond time scale [19]. The manufacturing of advanced micro-and nanostructures has been the domain of specialized scientific disciplines such as nanoelectronics [20], microfluidics [21], and photovoltaics [22]. Microstructures with features as small as 200 nm can now be easily manufactured by nonexperts using commercially available 3D direct laser writing instruments [23]. Furthermore, 3D large-scale simulations with enough spatial and temporal resolution to capture the details of the interaction are now possible thanks to recent advances in massiv...

Time-dependent nonlinear media, such as rapidly generated plasmas produced via laser ionization of gases, can increase the energy of individual laser photons and generate tunable high-order harmonic pulses. This phenomenon, known as photon acceleration, has traditionally required extreme-intensity laser pulses and macroscopic propagation lengths. Here, we report on a novel nonlinear material—an ultrathin semiconductor metasurface—that exhibits efficient photon acceleration at low intensities. We observe a signature nonlinear manifestation of photon acceleration: third-harmonic generation of near-infrared photons with tunable frequencies reaching up to ≈3.1ω. A simple time-dependent coupled-mode theory, found to be in good agreement with experimental results, is utilized to predict a new path towards nonlinear radiation sources that combine resonant upconversion with broadband operation.

We regret overlooking two important citations relevant to the current work, and wish to add these [1, 2]. We also cite [3], which reports crucial experimental parameters pertaining to [1], e.g. chamber pressure during water target experiment. To correct the oversight of missing references, the 4th paragraph of the introduction follows with modified and additional text underlined:Liquid targets have a number of attractive features for meeting these needs. Liquid targets can be rapidly delivered into the interaction region, and mitigate debris [31,[34][35][36]. This is well illustrated by the pioneering research in [1, 3], who, for the first time combined a kHz, femtosecond laser and liquid jet targets with a long-term vision of developing integrated sources of energetic radiation and particles for future applications. They reported the production of 9.25 keV x-rays from the interaction of a kHz, 50 fs pulsed laser interacting with a liquid Ga jet target. They also reported the use of CR39 film to record the production of 500 keV protons from the interaction of the kHz laser with an intensity of 3×10 16 W cm −2 focused on a 10-30μm diameter water jet, with a background chamber pressure of 0.7-3 mbar. The proton production efficiency of 10 −5 % was reported. Prior to switching to the liquid sheet target described in our current work, we attempted to obtain protons from the interaction of 15-30μm diameter water jets with a 40 fs pulsed laser focused to an intensity of 1×10 18 W cm −2 . We recorded many tracks on the CR39 film but, when a magnetic spectrometer was used, all of the tracks were shown to be due to electrons. As noted in this paper, we later discovered that the chamber background pressure required to produce a significant flux of protons was below the freeze point pressure of water.Skip to the end of the last sentence of the paragraph and add as the last sentence of the paragraph: the ability to generate a well collimated proton beam with proton energies greater than 500 keV has recently been demonstrated [2], using a high repetition rate 0.5 kHz, 3 mJ, 55 fs laser interacting with a solid target. The focus intensity was 2×10 18 W cm −2 . A proton beam was generated at the front surface of a rotating optical quality glass disk at a chamber pressure of 3×10 −3 mbar. AbstractLaser acceleration of ions to MeV energies has been achieved on a variety of Petawatt laser systems, raising the prospect of ion beam applications using compact ultra-intense laser technology. However, translation from proof-of-concept laser experiment into real-world application requires MeV-scale ion energies and an appreciable repetition rate (>Hz). We demonstrate, for the first time, proton acceleration up to 2 MeV energies at a kHz repetition rate using a milli-joule-class short-pulse laser system. In these experiments, 5 mJ of ultrashort-pulse laser energy is delivered at an intensity neaŕ -5 10 W cm 18 2 onto a thin-sheet, liquid-density target. Key to this effort is a flowing liquid ethylene glycol target formed i...