Double resonant plasma wakefields

Present work in Laser Plasma Accelerators focuses on a single laser pulse driving a non-linear wake in a plasma. Such single pulse regimes require ever increasing laser power in order to excite ever increasing wake amplitudes. Such high intensity pulses can be limited by instabilities as well engineering restrictions and experimental constraints on optics. Alternatively we present a look at resonantly driving plasmas using a laser pulse train. In particular we compare analytic, numerical and VORPAL simulation results to characterize a proposed experiment to measure the wake resonantly driven by four Gaussian laser pulses. The current progress depicts the interaction of 4 CO2 laser pulses, λlaser = 10.6μm, of 3 ps full width at half maximum (FWHM) length separated peak-to-peak by 18 ps, each of normalized vector potential a0 0.7. Results confirm previous discourse and show, for a given laser profile, an accelerating field on the order of 900 MV/m, for a plasma satisfying the resonant condition ωp = π tFWHM

Mid- and Far-Infrared Supercontinuum Generation in Bulk Tellurium Spanning from 5.3 μ\mum to 32 μ\mum

Supercontinuum generation is performed in the bulk semiconductor tellurium (Te) with a high-power picosecond CO$_2$ laser at peak intensities up to 20 GW/cm$^2$. The spectrum spans from the second harmonic of the pump at 5.3 $\mu$m to 32 $\mu$m. Stimulated Raman scattering along with self-phase modulation and four wave mixing are found to be the main nonlinear optical processes leading to the spectral broadening. Numerical simulations using the experimental conditions indicate that the nonlinear refractive index of Te, $n_{2,\textrm{eff}}$(Te) is about (40 $\pm$ 10) $n_{2,\textrm{eff}}$(GaAs), making this a very promising material for nonlinear optical devices.Comment: 7 pages, 4 figures, Submitted to Optics Letter

Multi-terawatt femtosecond 10 µm laser pulses by self-compression in a CO2 cell

We propose and numerically investigate a novel direct route to produce multi-terawatt femtosecond self-compressed 10 mu m laser pulses suitable for the next generation relativistic laser-plasma studies including laser-wakefield acceleration at long wavelengths. The basic concept involves selecting an appropriate isotope of CO2 gas as a compression medium. This offers a dispersion/absorption landscape that is shifted in frequency relative to the driving CO2 laser used for 10 mu m picosecond pulse generation. We show numerically that as a consequence of low losses and a broad anomalous dispersion window, a 3.5 ps duration pulse can be compressed to similar to 300 fs while carrying similar to 7 TW of peak power in less than 7 m. An interplay of self-phase modulation and anomalous dispersion leads to a similar to 3.5 times compression factor, followed by the onset of filamentation near the cell exit to get below 300 fs duration. (c) 2020 Optical Society of America under the terms of the OSA Open Access Publishing AgreementOffice of Naval ResearchOpen access articleThis item from the UA Faculty Publications collection is made available by the University of Arizona with support from the University of Arizona Libraries. If you have questions, please contact us at [email protected]

The UCLA helical permanent-magnet inverse free electron laser

The Inverse Free Electron Laser (IFEL) is capable, in principle, of reaching accelerating gradients of up to 1 GV/m making it a prospective accelerator scheme for linear colliders. The Neptune IFEL at UCLA utilizes a 15 MeV Photoinjector-generated electron beam of 0.5 nC and a CO2 laser with peak energy of up to 100 J, and will be able to accelerate electrons to 100 MeV over an 80 cm long, novel helical permanent-magnet undulator. Past IFELs have been limited in their average accelerating gradient due to the Gouy phase shift caused by tight focusing of the drive laser. Here, laser guiding is implemented via an innovative Open Iris-Loaded Structure (OILS) waveguide scheme which ensures that the laser mode size and wave front are conserved through the undulator. The results of the first phase of the experiment are discussed in this paper, including the design and construction of a short micro-bunching undulator, testing of the OILS waveguide, as well as the results of corresponding simulations

Control of the filament dynamics of 10 µm pulses via designer pulse trains

Atmospheric low-loss delivery of high-energy long wavelength picosecond duration pulses over multiple Rayleigh ranges will be dominated by the recently identified many-body coherent excitation-induced dephasing and avalanche based memory effects. We numerically illustrate this physics with pulse trains where prepulses gradually accumulate plasma preparing the medium for the main high-power pulse. The control over the nonlinear dynamics makes it possible to effectively avoid pulse splitting in the first few hundred meters, and deliver a wave packet with an improved spatiotemporal profile downstream. (C) 2019 Optical Society of AmericaOffice of Naval ResearchOffice of Naval Research [N00014-17-1-2705]; Air Force Office of Scientific ResearchUnited States Department of DefenseAir Force Office of Scientific Research (AFOSR) [FA9550-18-1-0368, FA9550-19-1-0032]12 month embargo; published online: 3 September 2019This item from the UA Faculty Publications collection is made available by the University of Arizona with support from the University of Arizona Libraries. If you have questions, please contact us at [email protected]