Taper-Integrated Multimode-Interference Based Waveguide Crossing Design

We present a design technique for a compact waveguide crossing by using a 90° multimode-interference (MMI) based waveguide crossing sandwiched by four identical miniaturized tapers where the power of the input guided mode is coupled into even modes of the MMI section at a specific power ratio and with different phases, thereby reducing the dimension of this waveguide crossing with imperceptible loss and crosstalk. Using the finite difference time domain method, we demonstrate that the MMI-based waveguide crossing embedded in short Gaussian tapers has a size 5426 nm × 5426 nm, insertion loss 0.21 dB, and crosstalk -44.4 dB at the wavelength of 1550 nm and broad transmission spectrum ranging from 1500 to 1600 nm.