Anisotropic scattering of discrete particle arrays.

Far-field intensities of light scattered from a linear centro-symmetric array illuminated by a plane wave of incident light are estimated at a series of detector angles. The intensities are computed from the superposition of E-fields scattered by the individual array elements. An average scattering phase function is used to model the scattered fields of individual array elements. The nature of scattering from the array is investigated using an image (theta-phi plot) of the far-field intensities computed at a series of locations obtained by rotating the detector angle from 0 degrees to 360 degrees, corresponding to each angle of incidence in the interval [0 degrees 360 degrees]. The diffraction patterns observed from the theta-Phi plot are compared with those for isotropic scattering. In the absence of prior information on the array geometry, the intensities corresponding to theta-Phi pairs satisfying the Bragg condition are used to estimate the phase function. An algorithmic procedure is presented for this purpose and tested using synthetic data. The relative error between estimated and theoretical values of the phase function is shown to be determined by the mean spacing factor, the number of elements, and the far-field distance. An empirical relationship is presented to calculate the optimal far-field distance for a given specification of the percentage error.

Acousto-optic modulation of a point-scatterer array.

Acoustic modulation of light scattering from a linear centrosymmetric array is analyzed by considering far-field contributions due to optoelastic (OE) effect and acoustically induced translation of the array elements. The modulated light intensity is shown to vary sinusoidally at the acoustic frequency when the physical constants representative of the above effects are within ranges of their physical limits. The OE and translation components of the acousto-optic (AO) signal are shown to be in phase quadrature, each exhibiting a double-sided maxima when expressed as a function of the detector angle.