Polarization/wavelength multiplexing devices realized by silicon nitride subwavelength grating structures

We present a wavelength multiplexing and polarization multiplexing device assisted by subwavelength grating (SWG), implemented on a 300-nm-tall silicon nitride (SiN) platform. The multiplexing device consists of three SiN waveguides- WG1, WG2 and WG3. The bridging waveguide WG2 between WG1 and output waveguide WG3 is designed into SWG structure, which executes the mode coupling thus multiplexing functions according to the principle of phase matching. The results are as follows: for wavelength multiplexing, the insertion loss (IL) is 0.54 dB and 0.58 dB at the center wavelength of O-band and C-band, which is 1310 nm and 1550 nm, respectively. The crosstalk (CT) is -12.5 dB and -23 dB at these two wavelength. The 1-dB bandwidth is larger than 170 nm for both bands. For polarization multiplexing, the IL is 0.44 dB and 0.64 dB at the wavelength of 1310 nm and 1550 nm, with the crosstalk lower than -16.2 dB and -22.8 dB. The 1-dB bandwidth is larger than 180 nm for the two bands.