Broadband SOI Grating Coupler Based on Sub-Wavelength Gratings with Low Back Reflection for Fiber-to-Chip Coupling of DWDM Signals

A design of a broadband and high-efficiency SOI grating coupler (GC) for the TE mode is demonstrated. The periodic segments of the GC use Subwavelength Gratings (SWGC), where the width of the silicon segments is much smaller than the operating wavelengths and the width varies along the length of the GC. The SWGC is optimized for TE polarization with a peak CE of-4.5 dB at a wavelength of 1550 nm, with a 1-dB bandwidth of 68 nm ranging from 1521.4 nm to 1589.4 nm and a 3-dB bandwidth of 119 nm from 1497.4 nm to 1616.4nm. The back reflections in the SWGC are suppressed to 22 dB. The broadband SWGC is integrated with cascaded ring resonators to demultiplex the incoming DWDM signal into individual channels and distribute them into sub-circuits. A layout of the GCs and ring resonators is generated, and system-level performance is evaluated.