Acoustic and electromagnetic wave interaction: Analytical formulation for acousto-electromagnetic scattering behavior of a dielectric cylinder

An analytical solution for the bi-static electromagnetic (EM) scattering fr om an acoustically excited vibrating dielectric circular cylinder is presen ted. The incident acoustic wave causes a boundary deformation as well as a dielectric inhomogeneity within the dielectric cylinder. First, a perturbat ion method is developed to calculate the EM scattering from a slightly defo rmed and inhomogeneous dielectric cylinder. Then, assuming the vibration fr equency is much smaller than the frequency of the incident EM wave, a close d form expression for the time-frequency response of the bi-static scattere d field is obtained. The solution for acoustic scattering from an elastic c ylinder is applied to give the displacement on the surface as well as the c ompression and dilation within the cylinder. Both the surface displacement and the variation in material density (dielectric constant fluctuation) wit hin the cylinder contribute to the Doppler component of the EM scattered fi eld. Results indicate that the Doppler frequencies correspond to the mechan ical vibration frequencies of the cylinder and that the Doppler components only become sizeable near frequencies corresponding to the natural modes of free vibration in the cylinder. These resonances depend only on the object properties and are independent of the surrounding medium. Thus, utilizing the information in the Doppler spectrum scattered by an acoustically excite d object vibrating at resonance could provide a means for buried object ide ntification.