Asymmetric light diffraction by pulsed ultrasonic waves

Abstract

Low-MHz, continuous ultrasonic waves traveling in a transparent medium cause light to be diffracted into discrete diffraction orders when light and sound propagation directions are normal to each other. When pulsed ultrasonic waves are used the diffraction orders split into secondary orders which are asymmetric with respect to the central diffraction order. This splitting is derived and a general expression provided for the intensity as a function of the ultrasonic pulse Fourier spectra. Examples are provided which demonstrate the degree of asymmetry for an exponential driving pulse and the convergence to the classic Raman–Nath results when the pulse approaches a continuous wave.

Analytical model for modulation of diffuse light by pulsed ultrasonic waves

“…The acoustical pressure in the medium is given by P ( r, t) = P 0 f (x, t), where P 0 is the pressure amplitude, and the pressure time dependence is represented by the function f (x, t). Analogous to previous work 16,17 where the acousto-optical effect caused by pulsed ultrasound is analyzed in a clear medium, we assume that the pressure time dependence function f (x, t) represents an infinite train of ultrasound pulses…”

Collinear dissipative weakly coupled acousto-optical states governed by the acoustic waves of finite amplitude in a two-mode medium with linear optical losses

“…While in solids, these studies have their roots in the 1970s within experimental verification of the Brillouin diffraction theory at very high acoustic frequencies in lead molybdate [6]. Asymmetric light scattering by ultrasonic pulses has been also studied [7]. Further, efforts have been made to describe the light diffraction by ultrasonic pulses using both analytical and numerical methods [8].…”