Compact and low-loss three-mode (de)multiplexer based on subwavelength grating-assisted asymmetric Y-junction on SiN loaded LNOI platform

We proposed a compact three-mode (de)multiplexer based on silicon nitride (SiN) loaded lithium niobate on insulator (LNOI) platform using a subwavelength grating (SWG)-assisted asymmetric Y-junction. The introduced SWG structure can effectively enhance the coupling strength of modes, shorten the device size. Meanwhile, the approximate matching of effective refractive indices between different modes is accomplished by designing the structural parameters. For TE(TM) modes, results indicate that the compact (de)multiplexer with a device length of 45 μm is achieved with an insertion loss of below 0.44 dB and crosstalk under −24.1 dB at a wavelength of 1.55 μm. And the (de)multiplexer can maintain stable performance within a certain range of fabrication tolerances. Due to the compact construction as well as flexible mode manipulation capability, the (de)multiplexer has broad application prospects in static routers and polarization multiplexing transmitters.