Resonant excitation of THz radiations by the interaction of amplitude-modulated laser beams with an anharmonic CNTs in the presence of static D.C. electric and magnetic fields

Abstract

We proposed an alternative scheme for the generation of terahertz (THz) radiation by using the rectangular array of horizontally aligned hollow anharmonic carbon nanotubes (CNTs) embedded on the base of the dielectric surface. Two transversely amplitude-modulated filamented laser beams interact with this array of CNTs in the presence of static D.C. electric and magnetic fields acting mutually perpendicular to each other as well as to the direction of propagation of the laser beams. Due to the non-uniform density of electrons in CNTs, the restoration force on the different electrons is different and this results in anharmonicity. This anharmonicity broadens the resonance peak. The laser beams also exert space periodic ponderomotive force and beat frequency ponderomotive force on the electrons of CNTs. Space periodic ponderomotive force is well balanced by the pressure gradient force to form a transverse density ripple. Nonlinear coupling between D.C. drift velocity of electrons and electron density in the plasma of CNTs results in enhancement in the generation of THz radiation. We have found that the normalized THz amplitude increases significantly with the increase of applied electric field from 10kV/cm to 20kV/cm and magnetic field from 11.50kG to 24.50kG.