Superlattice Arrayed Waveguide Grating in Silicon Nitride

Abstract

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 $1\times {8}$ 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 $\times0.6$ 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.