Magnetically enhanced THz generation by self-focusing laser in VA-MCNTs

Abstract

Magnetically enhanced terahertz (THz) radiations are generated on account of the self-focusing of the laser beam in the bunch of anharmonic Vertically Aligned Metallic Carbon Nanotubes (VA-MCNTs) embedded on the non-conductive sapphire or silicon on sapphire (SOS) substrate. The high-power Gaussian laser beam gets self-focused in the bunch of VA-MCNTs as the initial power of the propagating beam is greater than its critical power. The resulting laser beam interacts with the bunch of VA-MCNTs and as a result, the electrons of MCNTs experience a nonlinear ponderomotive force to show oscillatory behavior with resonant nonlinear transverse velocity. It produces the nonlinear current which drives the THz radiation generation. Enhanced THz generation is noticed in the regions where self-focusing becomes stronger. We have observed that an applied magnetic field, anharmonic behavior of MCNTs, self-focusing, and dimensions of MCNTs also pave the way for the enhancement of the normalized THz amplitude. The anisotropic behavior of the dielectric tensor in the presence of an externally applied static magnetic field also helps to enhance the THz amplitude. The results shown (by the beautiful graphs and well supported by the numerical simulation) in the present scheme indicate that the bunch of VA-MCNTs can play a diverse and significant role in the important applications of THz medical photonics by varying the values of various parameters. The emitted THz radiation has the ability to detect changes in the DNA of human beings because the frequency of the emitted radiation is observed to lie in the frequency region of molecular spectra of DNA and the corresponding energy of THz radiation is not high enough to damage the DNA by ionization.