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R. Kupfer, B. Barmashenko and I. Bar

Pulse self-modulation and energy transfer between two intersecting laser filaments by self-induced plasma waveguide arrays. Department of Physics, Ben-Gurion University of the Negev . R. Kupfer, B. Barmashenko and I. Bar. Computational physics in the eyes of experimentalists and theorists.

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R. Kupfer, B. Barmashenko and I. Bar

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  1. Pulse self-modulation and energy transfer between two intersecting laser filaments by self-induced plasma waveguide arrays Department of Physics, Ben-Gurion University of the Negev R. Kupfer, B. Barmashenko and I. Bar

  2. Computational physics in the eyes of experimentalists and theorists

  3. Ultrafast lasers 1fs = 10-15 sec = 0.000000000000001 sec Peak intensity > 1016 W/cm2 = 10000000000000000 W/cm2

  4. Nonlinear optics • Light interacts with light via the medium • Intensity dependent refractive index • Light can alter its frequency

  5. Propagation of ultrafast laser pulses in air High intensity regime () • High ionization • Relativistic self-focusing • Relativistic self-induced transparency Low intensity regime () • Self focusing due to the nonlinear refractive index • Plasma defocusing due to multiphoton ionization • Long filaments (up to 2 km) • “Intensity clamping” A. Couairon and A. Mysyrowicz, Phys. Rep. 441, 47(2006).

  6. Algorithm description • The pulse parameters can be controlled: Duration, intensity, spatial and temporal profile, linewidth, angle, waist and wavelength • The simulation area is surrounded by a perfectly matched layer. • Spectrum analysis using Goertzel algorithm • Only numerical assumptions Ei,j Jx i+1,j Hi,j Jy i,j+1 A. Taflove and S. C. Hagness, Computational Electrodynamics: The Finite-Difference Time-Domain Method, 3rd ed., Norwood, MA (2005). Initialize Particle Position Solve Poisson Equation Launch a Pulse on the Simulation Edge Solve Maxwell's Curl Equations Push Particles According to Lorentz force Calculate Current Density Caused by Particles Motion Analyze Spectrum of Outgoing Pulse on the Edge

  7. Relativistic self-focusing A. Pukhov and J. Meyer-ter-Vehn, Phys. Rev. Lett. 76, 3975 (1996). Simulation parameters: , and

  8. Single bubble regime • Ponderomotive force “pushes” electrons forming a region nearly void of electrons (ion channel) behind the laser pulse • The channel exerts an attractive Coulomb force on the blown out electrons causing them to accelerate into the bubble • A fast electron beam is formed • Mori and co-workers formulated the condition for this regime: • - speed of light, - pulse duration, - waist, - normalized vector potential and - plasma density Simulation parameters: , and W. Lu, M. Tzoufras, C. Joshi, F. S. Tsung and W. B. Mori, Phys. Rev. ST Accel. Beams 10, 061301 (2007). H. Burauet al. IEEE Trans. Plasma. Sci. 38, 2831 (2010). Pulse position Fast electron beam

  9. Objective – spectral and spatiotemporal evolution Comes in: • Pulse duration: • Spectral linewidth: ~ 20 nm • Gaussian shaped spectrum Comes out: • Pulse duration: Several pulses o (splitting) • Spectral linewidth: >> 20 nm (broadening) • Raman Stokes and anti-Stokes peaks and supercontinuum generation • Conical emission ?

  10. Objective – energy transfer between intersecting beams Y. Liu, M. Durand, S. Chen, A. Houard, B. Prade, B. Forestiers, and A. Mysyrowic, Phys. Rev. Lett. 105, 055003 (2010).

  11. Spectral and temporal evolution Simulation parameters: , and Simulation parameters: , and

  12. Energy transfer between intersecting beams

  13. Conclusions • PIC simulation of the spectral and spatio-temporal evolution of a single pulse in a high density plasma channel, as well as energy transfer between two intersecting pulses • The simulation results were found to be in agreement with previously obtained experimental results • Efficient frequency conversion and energy transfer can be achieved in a compact and simple setup and over very short distances • It is anticipated that this model will be able to simulate laser-plasma interactions even in more complicated geometries and to predict the behavior under different conditions • Future work • Characterization of localized surface plasmons in nanoparticle arrays • Second harmonic generation from irradiated solid targets • Raman and Brillouin scattering in liquids

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