We consider acousto-optical Bragg scattering from inhomogeneous material composites of bubbles, shells, or voids generated within liquids. Because such media are compressible, their diffractive acoustic grating efficiencies can be improved in comparison to those of more common homogeneous far-infrared transmitting materials. Fundamental acoustic properties of mixtures containing bubbles, shells, and voids are analyzed by extending previous theories to these experimentally realizable configurations. The dispersive character of acoustic propagation in such multicomponen.t media is examined and is shown to lead to observable consequences in experiments such as far-infrared frequency mixing. For infra-red applications it is useful to form bubbles in nonabsorbing host media, such as nonpolar liquids. From this point of view, metastable nitrogen bubbles, having diameters of order 5-35 have been introduced into a flowing fluid consisting of several percent of low vapor-pressure silicone oil in 1, 1, 2-trichloro-1, 2, 2-trifluorethane. Our technique has produced mixtures having 10-20 volume percent bubbles.
|