A polarization-insensitive 1310/1550-nm demultiplexer based on sandwiched multimode interference waveguides

A polarization-insensitive dual-wavelength demultiplexer based on sandwiched multimode interference waveguides is presented. Polarization-insensitive multimode waveguides are achieved first by choosing a suitable refractive index of the SiNx middle region. The demultiplxing function is then realized by adjusting the width and length of the multimode region. Simulation results obtained from three-dimensional beam-propagation method show that the demultiplexer can work at 1310- and 1550-nm bands for both polarizations simultaneously with a low insertion loss and a broad bandwidth.