Nonlinear codirectional guided wave mode conversion in grating structures

The authors discuss the operational characteristics of a new all-optical device, based on a nonlinear grating, potentially capable of all-optical switching between dissimilar waveguide modes. The use of a grating allows for a substantial reduction in switching-power requirements, still permitting complete power-dependent mode-conversion. An unexpected feature is that efficient switching requires detuning from the low-power wave vector matching condition. The switching behavior is very sensitive to wavelength detuning, both from the Bragg condition and from the higher-order mode cutoff condition. Furthermore, operation of the device is strongly nonreciprocal with respect to interchanging the mode launching condition.<
>