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Electron acceleration due to beating of two slightly different frequency LP (Linearly polarised) laser pulses with finite spot size in a vacuum has been studied. In this scheme, two lasers are incident at a point with some angle, due to beating of LP lasers constructive interference occurs. The resultant electric and magnetic field of this constructive interference helps in acceleration of pre-accelerated electron which is injected and trapped by the field. In this paper, we have seen the effect of linear and quadratic chirp on laser beat wave acceleration in vacuum and a comparison between the two is made for effective energy gain.

Second harmonic generation induced by surface plasma wave at the metal-semiconductor interface has been investigated. A thin layer of metals like Cu and Al have been considered in attenuated total reflection configuration(ATR) with a thin layer of semiconductor n-InSb over it. The study has been done in the presence of a wiggler magnetic field. The field provides additional momentum to the photons which help to attain phase matching conditions, leading to a resonant process of harmonic generation. Numerical analysis under given conditions show that Cu-InSb is the better choice for the harmonic generation as compared to Al-InSb.

In present study we have investigated the third harmonic generation (THG) of self-focused Hermite-cosh-Gaussian (HchG) laser beam, propagating through plasma. When intense short pulse laser propagates through plasma results ponderomotive force on electrons due to which electrons move away from the axial region, creating a low density plasma region. Due to electrostatic force, electrons gain oscillatory velocity and results density perturbation. Density oscillations at frequency 2ω1 couple with oscillatory velocity of electrons, at the fundamental frequency of incident laser result THG. Due to phase mismatch with the incident pulse, the third harmonic pulse is of smaller amplitude. Wiggler field satisfy the resonance condition by providing additional momentum to the photon of third harmonic pulse and this result increase in the normalized amplitude of third harmonic pulse. In the present study the study of beam width parameter with normalized propagation distance at optimum values of different laser parameters has been studied. We derived the coupled differential equation for the normalized amplitude, A'30/A 10, of third harmonic pulse. We analysed the efficiency of third harmonic pulse with ξ at optimum values of normalized intensity of fundamental laser.

In the present model, a detailed theoretical investigation of the nonlinear current density produced by beating of chirped pulse lasers in plasma having spatial ripple density is conducted. In our mechanism, we consider two Gaussian lasers with electric fields E → 1 and E → 2 propagating along z ^ , polarized along ŷ direction. The lasers have a linear frequency chirp and the frequency Ω1 and Ω2can be chosen as the required frequency range. A transverse nonlinear ponderomotive force is experienced by the plasma electrons due to the lasers beating in plasma. As a consequence, plasma electrons get an oscillatory velocity that paired with the density ripple to generate a stronger transient transverse nonlinear current. Our theoretical simulation unveil that by optimizing the chirp parameter a prominent change in nonlinear oscillating current is depicted.

In this paper, we develop an analytical formalism for THz generation from Laser filaments in the presence of static electric field in the magnetized collisional plasma. Two femtosecond laser pulses with different frequencies undergo filamentation in magnetized collisional plasma to have non-linear coupling in the presence of transverse static electric field. This results in balancing action of static ponderomotive force with pressure gradient force and forms transverse density ripple and non-linear ponderomotive force couple with density ripple to provide strong non-linear transverse current which results in excitation of THz Radiations at resonance. This coupling is further enhanced by electric static field.