Study On Inhomogeneous Spatial Distribution Of Scattering Light Intensity Of Bragg Acousto-optic Interaction

A review of the principles of acousto-optic interaction (AOI) with the main features of crystal acoustics and optics is given, which includes Bragg acousto-optic interaction and Raman-Nath acousto-optic interaction. For Bragg acousto-optic interaction (Bragg-AOI) in homogenous medium, the acoustic field is viewed as a piece of'volume grating'. When the incident light field and acousto-optic field meet Bragg conditions, only the zeroth and first orders (or minus first orders) scattering fields will be produced and both of beam spots are the same with the incident beam's, which has been tested by the theory of grating diffraction.From the structure of the acousto-optic cells and the fact of the finite sizes of acousto-optic crystal and transducer, a model of the acoustic field is built. That is the acoustic amplitude decreases along the width of transducer in the form of Gaussian function which includes a parameter-attenuation factor. Derived from the Maxwell equations, coupled-wave equations about Bragg-AOI are obtained. The three-dimensional spatial intensity distribution of scattering light field is calculated with finite difference method. According to the numerical results, the spatial intensity distribution of scattering fields will be greatly influenced by the value of the attenuation factor, and be inhomogeneous along the direction of the width of transducer. The scattering beams spot type is greatly changed.Finally, conclusions and expectations on the study of the spatial intensity distribution of acousto-optic scattering field in three dimensions are given.