Abstract

When optically induced perturbations of some scalar parameter (e.g., temperature) of an anisotropic medium result in changes in its optical properties with different signs for different eigenwaves (e.g., e- and o-waves), the medium is said to possess non-Lagrangian or diagonal-bipolar nonlinearity.^1-2 The corresponding nonlinear induction cannot be obtained then by variation of any Lagrangian. What does allow nonlinear optical processes to be performed avoiding particular restrictions imposed by conservation laws? Stationary energy exchange between two counterpropagating equal-frequency waves thus turns out to be possible.

© 1991 Optical Society of America