Superlattice Arrayed Waveguide Grating in Silicon Nitride

Emerging silicon nitride (SiN) nanophotonic circuits are an advantageous technology for dense wavelength division multiplexing systems but they have larger footprints than silicon-on-insulator devices due to the lower index contrast. We present an ultra-compact 100 GHz 1 × 8 SiN arrayed waveguide grating (AWG) enabled by the novel concept of the waveguide superlattice. A waveguide superlattice is a periodic structure consisting of alternate waveguide geometries with negligible parasitic couplings. Thanks to the densely arrayed waveguides, this superlattice AWG (SL-AWG) has a compact footprint of 4.3 mm × 0.6 mm, which is more than two times smaller than a conventional AWG with similar performance implemented previously on the same SiN platform. The SL-AWG also shows a low insertion loss of 3.4 dB and a low crosstalk of -18 dB.