One-dimension dual-band chirped grating coupler with bottom metal reflector

Emerging applications such as next-generation passive optical networks (PONs) require low-cost, high-performance dual-/multi-band transceivers. There are two ports in one-dimensional grating couplers (GCs), which theoretically enable wavelength division multiplexing/demultiplexing (WDM) for two bands with the advantages of a compact footprint and ease of fabrication. A one-dimensional dual-band chirped grating coupler (DB-CGC) integrated with a bottom metal reflector is proposed in this paper. The device enables efficient fiber-to-waveguide coupling and supports WDM for both the C- and O-bands. A dual-band uniform grating coupler (DB-UGC) on a 340 nm SOI platform is designed first. Then, a chirped grating period is applied to the DB-UGC. Through numerical calculation and analysis, the optimal incident angle is determined to address the phase mismatch between the C- and O-bands caused by the chirped structure, which improves the coupling efficiency for both bands. Then an aluminum reflector is integrated beneath the grating to recycle the optical power leaking into the substrate. The 3D-FDTD simulations confirm that the coupling efficiencies reach −1.08 dB at 1305 nm and −1.07 dB at 1536 nm, with 3 dB bandwidths of 49 and 63 nm, respectively.