Effective matching in a nonlinear directional coupler with waveguide mismatching and nonuniform nonlinearity.

A variable-coupling-coefficient nonlinear directional coupler with mismatching and nonuniformity is studied by means of coupled mode equations with effective mismatching. It is pointed out that the effective mismatching can be cancelled out for any given input power by properly adjusting the magnitudes of the mismatching and nonuniformity. Numerical examples are given to show that complete power transfer between two waveguides can be achieved for a mismatched and nonuniform nonlinear directional coupler and for a Gaussian as well as an exponential variable-coupling-coefficient nonlinear directional coupler.

Variable coupling coefficient nonlinear directional couplers with self-focusing and self-defocusing nonlinearity.

Nonlinear directional couplers (NLDCs) with a variable coupling coefficient (VCC) in self-focusing and self-defocusing materials are investigated. Specifically, the Gaussian type VCC NLDCs are studied in detail. The results show that the responses of the VCC NLDCs on self-focusing and self-defocusing materials are different, especially when input power is high. The coupled-mode theory can also be used to predict the characteristics of the VCC NLDC on self-focusing material, even when input power is high.

Arc-shaped waveguide switch based on the third-order nonlinear effect.

A kind of arc-shaped all-optical waveguide switch is proposed for the first time, to the best of our knowledge, and the switching characteristics of it are investigated by means of the beam propagation method. The effects of saturation and loss on the characteristics of the switch are discussed.