A broadband, low-crosstalk and low polarization dependent silicon nitride waveguide crossing based on the multimode-interference

Abstract

A silicon nitride waveguide crossing based on multimode-interference is designed and fabricated. By optimizing the structure parameters with finite difference time domain method, 0.3 dB insertion loss and −75 dB crosstalk at 1550 nm are obtained. Then the designed waveguide crossing is fabricated based on the double strip silicon nitride waveguide. The measured results show the insertion loss and crosstalk are about 0.6 dB and below −42 dB, respectively, in the wavelength range of 1520 nm∼1640 nm with low polarization dependence. The waveguide crossing could be a key building block for the silicon nitride waveguide platform.