Dual-Wavelength-Band Grating Coupler on 220-nm Silicon-on-Insulator With High Numerical Aperture Fiber Placed Perfectly Vertically

We propose and design a novel dual-wavelength-band grating coupler on 220-nm-thick silicon-on-insulator and experimentally investigate its capability to couple two wavelength bands simultaneously under surface-normal fiber placement. Such dual-wavelength-band operation take advantage of a dual-etch grating design not only with increased directionality but also with unique diffraction angle dispersion characteristics for the two targeted wavelength bands. The role of high numerical aperture fiber is theoretically investigated, leading to reduced angular sensitivity in general and subsequently increased coupling efficiency for our proposed dual-wavelength-band operation scheme. Our device is further fabricated using 248-nm deep-UV lithography on an 8-inch wafer for verification. The peak coupling efficiency is measured to be –5.0 dB at 1275 nm and –5.9 dB at 1519 nm for O-band and S/C-band respectively.