Diffraction of light by two ultrasonic beams of frequency ratio 1:2, beyond the Raman-Nath diffraction regime.

Light diffraction by two ultrasonic waves of frequency ratio 1:2 is examined beyond the Raman-Nath diffraction regime. Measurements were taken of +/- 1 order diffracted light intensities for some Raman-Nath parameter values, as a function of the phase shift between the sound beams. The experimental results obtained are discussed and compared with relevant theoretical predictions. Within the experimental conditions, a quite good quantitative agreement between the experimental data and the appropriate theoretical expectations is observed.