Exact modal analysis and optimization of N/spl times/N/spl times/1 cascaded waveguide structures with multimode guiding sections

Cascaded multimode interference waveguide devices are analyzed to predict their switching properties. The results obtained using an exact modal analysis of an infinite slab model of these structures are compared to those found using simple approximations. Using this model, design parameters for both 2/spl times/2/spl times/1 and 8/spl times/8/spl times/1 switching structures are optimized; robustness of the numerical optimization algorithm is discussed. Sensitivity of device transmission performance to lengths and widths of each of the multimode regions, phase shifts in the interconnect regions, and wavelength are presented for the optimized devices. The deviations of the multimode region lengths found using simple approximations from those found by optimizing the model are also presented.