Theoretical studies for special states of cascaded quadratic nonlinear effects

From the viewpoint of photon flux, the evolution of phases and intensities in the eigenmode state in three-wave mixing (TWM) is studied, and the requi rements for the initial phases and incident intensities in this state are d erived. Another special state in which there is an exchange of intensities without a phase change in the TWM is also investigated, for the first time to the authors' knowledge. By use of the two special states of cascaded qua dratic nonlinear effects, an all-optical switch based on the push-pull Sagn ac loop is proposed, and its properties are calculated. The numerical resul ts show that the switch is quite stable, and the intensity and phase of the output signal can easily be established and controlled. (C) 2001 Optical S ociety of America.