Abstract-High-power terahertz radiation generation by beating of two co-propagating super-Gaussian laser beams in cluster plasma

Ram Kishor Singh, Monika Singh and Satish Kumar Rajouria

http://iopscience.iop.org/article/10.1088/1555-6611/aabffd

This communication presents the theoretical investigation of resonant terahertz (THz) radiation generation by two co-propagating laser beams having super-Gaussian intensity profile in a clustered plasma. The cluster electrons experience a ponderomotive force at beat wave frequency in the axial direction as well as perpendicular to the propagation direction of the beams due to the nonuniform intensity profile of laser beams. This force causes the acquisition of a nonlinear oscillatory velocity to the cluster electrons. A strong nonlinear transverse current density at beat wave frequency arises on account of the coupling of nonlinear velocity with density ripple, which drives a THz wave in the propagation direction of the laser beam. The THz yield strongly depends on the index of the super-Gaussian beams as well as the amplitude of density ripple. We report generated THz wave efficiency of 10−3 with the help of the optimizing laser beams and cluster plasma parameters.

Abstract-Cherenkov terahertz surface plasmon excitation by an electron beam over an ultrathin metal film

Journal of Applied Physics

Pawan Kumar1,a), Rajeev Kumar2, and  Satish Kumar Rajouria
http://aip.scitation.org/doi/abs/10.1063/1.4971346
The mechanism of Cherenkov excitation of terahertz (THz) surface plasma wave (SPW), by a relativistic electron beam propagating over an ultrathin metal film deposited on glass,is investigated. The SPW field falls off exponentially in vacuum as well as glass, while the surface plasmon resonant frequency is lowered by the reduction of film thickness. The SPW field causes density bunching of the beam leading to current modulation and generation of THz radiation via the Cherenkov interaction. The frequency of the THz decreases with the energy of the beam, whereas the growth rate increases.

Paper-Effect of pulse slippage on beat wave THz generation in a rippled density magnetized plasma

Manoj Kumar, Satish Kumar Rajouria and Magesh Kumar K K

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manojailum@gmail.com

Department of Physics, Indian Institute of Technology, Delhi, New Delhi-110016, India 

http://iopscience.iop.org/0022-3727/46/43/435501

Paper

Beat wave excitation of terahertz radiation by nonlinear mixing of two laser pulses in a ripple density magnetized plasma is investigated allowing for the effect of pulse slippage. The lasers' ponderomotive-force-induced electron drift couples with the density ripple to produce a nonlinear current that resonantly drives the terahertz at the beat frequency. Density ripple provides the phase matching while the magnetic field, transverse to the direction of laser propagation, provides a transverse component to current density. However, the group velocity mismatch between the lasers and the terahertz radiation leads to slippage of the latter behind the laser pulses leading to saturation of the terahertz amplitude.