Focusing/defocusing of intense laser beam in cold quantum plasma

The quantum effects on the propagation of an intense laser beam in an inhomogeneous cold quantum plasma (CQP) is investigated. As the intensity of laser beam increases the relativistic mass effect as well ponderomotive expulsion of electron modifies the dielectric function of the medium due to which the medium exhibits nonlinearity. Quantum plasma enhances nonlinear phenomena remarkably and hence cannot be ignored when density of the plasma electrons becomes very high that is when de Broglie wavelength of charged particle is equal to or greater average interparticle distance or equivalently temperature T is less than or equal to Fermi temperature. Based on WKB and paraxial theory, the steady state solution of an intense Gaussian electromagnetic beam is studied in CQP. By employing the expression for the dielectric function of CQP, a differential equation for beam width parameter with distance of propagation is evaluated