EM Scattering from a simple water surface composed of two time-varying sinusoidal waves

Abstract

Electromagnetic (EM) scattering from a simple water surface composed of two time-varying sinusoidal waves when it is illuminated by of a plane EM wave or a Gaussian beam are investigated respectively and some novel phenomena have been found. Firstly, on the basis of the traditional Bragg scattering theory, the power of the scattering is proportional to the spectrum density of the water wave which resonates with the incident EM wave. However, the scattering field from the water surface composed of two time-varying sinusoidal waves reveals that the resonant scattering field would also be affected by the non-resonate wave. The simulations demonstrate that the Bragg resonant scattering field even would disappear when the amplitude of the non-resonant water wave is equal to some specific values. Another phenomenon is that the spectrum of the scattering field would be distorted seriously by the edge effect when the illuminated area of the water wave is finite. In this case, if the plane EM wave illuminates the water surface, the scattering field echo will not only have the spectral peak corresponding to the phase velocity of the water wave, but also have other harmonic peaks due to the edge effect. By contrast, if the incident EM wave is a Gaussian beam, the harmonic peaks would be well dampened.