Nonlinear Absorption of Cosh-Gaussian Laser Beam in Arrays of Vertically Aligned Carbon Nanotube

Abstract

The nonlinear absorption of high power cosh-Gaussian laser beam in arrays of vertically aligned carbon nanotube is theoretically investigated. Herein, the cosh-Gaussian (ChG) laser beam propagates perpendicular to the length of carbon nanotube arrays and is mounted on a planer surface. As the high-power laser beam interacts with the carbon nanotube, the electrons associated with it might be excited, undergo the ionized state, and formed the preformed plasma. By the result, the electron cylinder is displaced with respect to ion cylinder. The laser electric field produces the electrostatic restoration force due to the excursion of electrons with respect to ions. This restoration force causes to arise of nonlinearity. An analytical expression of effective nonlinear absorption coefficient of the cosh-Gaussian laser beam is derived. The absorption coefficient is resonantly enhanced as the laser beam frequency approaches near the surface plasmons frequency \(\omega \sim {\omega }_{\mathrm{pe}}/\sqrt{2}\). The presence of collisional frequency between electrons and ions leads to strengthen the absorption process. The laser beam decentered parameter associated with hyperbolic cosine term is a sensitive and effective parameter. This parameter much affects the effective absorption coefficient. The graphical results reveal that the absorption coefficient is strongly dependent on laser beam parameters and carbon nanotube array parameters. This enhanced and tunable absorption process of the cosh-Gaussian laser beam might be applicable in electron heating, self-focusing, and high harmonic generation process.