NONLINEAR-OPTICAL EFFECTS IN FERROFLUIDS INDUCED BY TEMPERATURE AND CONCENTRATION CROSS-COUPLING

Both experiment and numerical calculation were performed to study the nonlinear optical (NLO) effects in ferrofluids consisting of magnetic particles suspended in an organic solvent. We show that, in contrast t o all the mechanisms responsible for NLO phenomena known so far, the n ovel NLO effects in ferrofluids in the zero applied field can be expla ined by the cross coupling between the temperature of the system and t he concentration of particles through thermophoresis, which in turn le ads to the spatial distribution of the refractive index. This NLO effe ct is enhanced by applying a moderate magnetic field whose mechanism i s unclear so far. (C) 1998 American Institute of Physics.