Three-dimensional wavelength-division multiplexing interconnects based on a low-loss Si_xN_y arrayed waveguide grating

We fabricate three-dimensional wavelength-division multiplexing (3D-WDM) interconnects comprising three Si_xN_y layers using a CMOS-compatible process. In these interconnects, the optical signals are coupled directly to a Si_xN_y grating coupler in the middle Si_xN_y layer and demultiplexed by a 1 × 4 Si_xN_y array waveguide grating (AWG). The demultiplexed optical signals are interconnected from the middle Si_xN_y layer to the bottom and top Si_xN_y layers by four SiO_xN_y interlayer couplers. A low insertion loss and low crosstalk are achieved in the AWG. The coupling losses of the SiO_xN_y interlayer couplers and Si_xN_y grating coupler are ∼1.52 dB and ∼4.2 dB, respectively.