Low-loss multimode-interference-based crossings for silicon wire waveguides

We report multimode-interference (MMI)-based crossings in high-index-contrast silicon wire waveguides. Our experiments show an MMI crossing of similar to 0.4-dB insertion loss, which suggests similar to 0.9-dB improvement from a control plain crossing of the same size and refractive index contrast. We also experimentally observe significant crosstalk suppression in our MMI crossing. The MMI crossing transmission exhibits wavelength dependence of less than 0.2 dB within the 1520-1580-nm wavelength range.