Design and fabrication optimization of a 4-channel polarization-independent AWG demultiplexer for CWDM system based on a 3-µm SOI platform

Coarse wavelength division multiplexing (CWDM) systems are widely used in telecommunications and data center interconnects. The polarization-sensitive characteristics of the demultiplexer at the receiving end lead to significant optical power loss in the signal transmission link and increase the complexity of the packaging process. In this work, a 4-channel polarization-independent arrayed waveguide grating (AWG) was designed for CWDM systems, which was realized by ridge waveguides on the SOI platform with 3-µm-thick top Si. Compared with the conventional ridge waveguide with a dual-surface structure, the quasi-single-mode ridge waveguide was designed with a single-surface structure and fabricated by a simple one-step dry etching process. The AWG device performed well while working in O-band. The fabricated demultiplexers were experimentally measured to have minimum insertion losses of 0.68 dB, channel crosstalk of better than -19 dB, and polarization-dependent loss of 0.31 dB.