Design of efficient concave diffraction grating on 220 nm SOI platform for hybrid WDM–PDM​ (de)multiplexing

An efficient concave diffraction grating (CDG) for multi-wavelengths and dual polarizations is proposed and demonstrated on 220 nm SOI platform with systematic analyzation and simulation. The multilayer dielectric reflector is designed as an alternative to conventional deep-etched tooth to provide high reflectance with polarization insensitivity. Simulation results indicate that with proper selection of incident angles, the grating designed by this approach shows excellent performances in terms of diffraction efficiency, channel uniformity and next-channel crosstalk for both TE and TM polarizations. A comparative analysis between different grating tooth configurations and a detailed discussion about the fabrication tolerances are also presented. This design can be applied to wavelength and polarization hybrid multiplexing to further enhance the link capacity of optical transmissions and interconnects.