LAUSR

Abstract In acousto-optic imaging, the ultrasound-induced optical phase modulation has been widely used in the imaging of biological tissue. However, in Raman-Nath diffraction, the phase of diffracted light has not attracted much attention. Additionally, each order of diffraction has been simply treated as a plane light wave with optical phase shift, and the intensity of diffraction orders hence has been considered to be constant. Then, the phase shift is independent on the diffraction path of light wave in the acousto-optic interaction zone and the corresponding refractive index and the power of the ultrasound wave. Recently, we observe experimentally that the intensity of diffraction orders varies periodically with time. We hence study the periodic variations in depth. It is found that the diffracted light has an ultrasound-induced phase modulation and the periodic variations are due to the phase modulation.