Novel design of multi-mode-interference crossings for periodic dielectric waveguides

A novel right angle crossing of periodic dielectric waveguides based on the multi-mode interference effect is proposed and numerically simulated, which can effectively improve performances of periodic dielectric waveguide crossing by both transmission enhancing and crosstalk reducing. For optical communication wavelengths near 1.55 μm, with an area of 1.9 μm×1.9 μm, the transmission was enhanced to be above 95%, and the crosstalk at the same time was lowered to below −20 dB. The best transmission and crosstalk were achieved at a wavelength of 1.57 μm with a value of 97.3% and −23 dB, respectively. We also show that the proposed crossing structure has the potential to achieve 1×N or M×N crossing in a relatively direct way. A simple 1×2 and 2×2 structure were proposed and studied, which were with good performances of high transmission and low crosstalk, too.