Parametric excitation of surface plasma waves by stimulated Compton scattering of laser beam at metal-free space interface

Abstract

AbstractAn obliquely incident high-power laser (ω0,k0z) on the metallic surface can resonantly excite a surface plasma wave (SPW) (ω1,k1z) and a quasi-electrostatic plasma wave (ω,kz) inside the skin layer at the phase-matching conditions of frequency ω1= ω − ω0and wave numberk1z=kz−k0z. The oscillating electrons in the skin layer couples with the seed SPW and exert non-linear ponderomotive force on electrons at the frequency of quasi-static mode. Density perturbations due to quasi-static mode and ponderomotive force associate with the motion of electrons (due to incident laser) and give rise to a non-linear current by feedback mechanism. At ω/kz~vF(wherevFis the Fermi velocity of metal) this non-linear current is responsible for the growth of SPW. The maximum growth of the present process (≅1.5 × 1012s−1) is achieved at incident angle θ = 42° for laser frequency ω0= 2 × 1015rad/s. Growth of SPW enhances from 1.62 × 1011to ≅1.5 × 1012s−1as the magnetic field changes from 12 to 24 MG. The excited SPW can be utilized for surface heating and diagnostics purpose.