Theory of mixed-polarization spatial solitons in anisotropic cubic media
AlGaAs is an attractive material system for the study of the dynamics of Kerr spatial solitons, having a nonlinear coefficient of 1000 times that of silica around the communication wavelength of 1.55 /spl mu/m. However, there are several differences between AlGaAs and silica when the polarization dependence of nonlinear refraction is considered. Cubic semiconductors can display an anisotropic third-order nonlinearity (although in terms of linear optics they are nonbirefringent) and are also usually exploited in the vicinity of an optical resonance (e.g., just below the half-bandgap), so that Kleinmann symmetry cannot be assumed. On considering the propagation of two orthogonal polarization components in such a medium, one obtains not only self-phase modulation, cross-phase modulation, and four-wave mixing, but now with an orientation dependence, but also terms that contribute to anisotropy.