The nonlinear susceptibilities of a heterogeneous medium are calculated by using a generalization of the standard T-matrix approach. Results for the susceptibilities for degenerate and nondegenerate four-wave mixing and nonlinear absorption are obtained. These are evaluated explicitly for a medium with nonlinear spherical grains. The role of various resonances in the generation of the signals is discussed. In the special cases of low concentration of inhomogeneities, present results agree with those of Flytzanis and co-workers [Opt. Lett. 9, 344 (1984); 10, 511 (1985); J. Opt. Soc. Am. B 4, 5 (1987)].

• Received 5 May 1988

DOI:https://doi.org/10.1103/PhysRevA.38.5678