Fazel Jahangiri

Optimizing chirped laser pulse parameters for electron acceleration in vacuum

Electron dynamics in the field of a chirped linearly polarized laser pulse is investigated. Variations of electron energy gain versus chirp parameter, time duration, and initial phase of laser pulse are studied. Based on maximizing laser pulse asymmetry, a numerical optimization procedure is presented, which leads to the elimination of rapid fluctuations of gain versus the chirp parameter. Instead, a smooth variation is observed that considerably reduces the accuracy required for experimentally adjusting the chirp parameter.

Terahertz radiation generation through the nonlinear interaction of Hermite and Laguerre Gaussian laser beams with collisional plasma: Field profile optimization

The nonlinear interaction of Hermite-Gaussian and Laguerre-Gaussian (LG) laser beams with a collisional inhomogeneous plasma is studied, and the amplitude of the emitted terahertz (THz) electric field is evaluated. The effects of laser beams and plasma parameters, including the beams width, LG modes, the plasma collision frequency, and the amplitude of density ripple on the evolution of THz electric field amplitude, are examined. It is found that the shape of the generated THz radiation pattern can be tuned by the laser parameters. In addition, the optimum values of the effective parameters for achieving the maximum THz electric field amplitude are proposed. It is shown that a significant enhancement up to 4.5% can be obtained in our scheme, which is much greater than the maximum efficiency obtained for laser beams with the same profiles.

Gain and bandwidth investigation in dual-pumped non-collinear optical parametric chirped pulse amplification

Dual-pumped non-collinear parametric amplification of a chirped laser pulse is numerically studied by employing the pump beams of different wavelengths. Our results reveal that the output bandwidth and the efficiency-bandwidth product are improved, when non-collinear angles and phase matching conditions are separately optimized for each individual pump beam. Moreover, by studying the dependence of the bandwidth of the amplified signal on the pump intensity, gain stability and its fluctuations are compared in small signal gain and saturation regimes. It is verified that the effective interaction length in this dual-pumped configuration is reduced as a consequent of increased bandwidth, compared to that in a single pump scheme.

Electron acceleration in vacuum by optimized nonlinearly chirped laser pulse

Electron acceleration in vacuum by a nonlinearly chirped laser pulse is studied and it is shown that utilizing optimized higher order chirp functions leads to enhancement of the electron energy gain.