We point out some inconsistencies in the usual coupledmode formulation employed to model the nonlinear behavior of symmetric directional couplers. In particular, we show that special care is required when neglecting some of the nonlinear terms in the equations.
© 1990 Optical Society of America
Francisco J. Fraile-Pelaez and Gaetano Assanto, "Coupled-mode equations for nonlinear directional couplers," Appl. Opt. 29, 2216-2217 (1990)