Polarization-dependent optical nonlinearities in fractional-layer superlattices

We measure the room-temperature polarization-dependent nonlinear absorption and refractive-index spectra of a (Al0.5Ga0.5As)1/2(GaAs)1/2 fractional-layer superlattice (FLS) structure grown by metalorganic chemical vapor deposition. The anisotropic nonlinear effects between the directions parallel and perpendicular to the superlattice give rise to a nonlinear optical birefringence in the plane of the growth surface. From our measurements using a femtosecond optical pulse, we derive the magnitude and spectral shape of the nonlinear optical birefringence. We describe the basis of an all-optical polarization rotation switch using the FLS structure.