Abstract

Large, nonresonant optical-Kerr-Iike non-linearities are a basic requirement for all- optical switching and related applications.¹ In addition to the nonlinearity that is proportional to χ⁽³⁾, there is another important contribution that occurs only in noncentro- symmetric materials. This contribution induces a nonlinear phase shift in nearly- phase-matched second-harmonic-generation interactions and other parametric processes.^2,3 Such effects were first observed in high-power pulsed second-harmonic- generation experiments. Recently the potential for all-optical switching was realized and large nonlinear phase shifts due to cascading were observed for the first time in potassium titanyl phosphate (KTP) waveguides.³ Unexpectedly large nonlinear-refractive-index changes observed in fibers of 4-(N,N-dimethylarnmo)-3-acetamidonitrobenzene (DAN) could also be explained by cascaded nonlinearities.⁴

© 1995 Optical Society of America