Nonlinear microwave susceptibility measurement of an artificial Kerr medium

A suspension of short graphite fibers was shown to provide an effective medium for nonlinear microwave interactions. Using a 18-GHz pump beam with up to 20 W continuous power, changes in the 94-GHz refractive index were measured by interferometry. The induced birefringence and anisotropic absorption indicate an alignment of the fibers with the electric field of the pump beam. The resulting nonlinear refractive index coefficient of n2=2.6×10−4 cm2/W is of sufficient magnitude to demonstrate microwave bistability.