Description

This book presents a theoretical investigation of coherent radiation generation by particle beams and nonlinear mixing of lasers. The focus is on the broadband generation of microwaves and terahertz waves by power enhancement in sheath helix loaded travelling wave tube, introducing plasmas in the interaction region. In the terahertz band we examine the resonant excitation of terahertz radiation by beating two Gaussian laser beams in a magnetized plasma channel. As an alternative route we study the nonlinear mixing of two infrared lasers of frequencies and propagating in the TM/TE mode in a rippled density semiconductor waveguide to resonantly excite terahertz radiation. Two parallel semiconductor plates, separated by a short distance, are seen to be suitable for the excitation of Terahertz waves by a mildly relativistic electron beam. A relativistic sheet electron beam propagating through the space between the planes resonantly excites a THz surface plasma wave (SPW). The efficacy of n-InSb is examined for linear mode conversion of terahertz radiation into a surface plasma wave. The semiconductor surface is taken to be rippled and magnetized.