CMOS-compatible high efficiency double-etched apodized waveguide grating coupler.

We present a high efficiency double-etched apodized fiber-to-waveguide grating coupler on a silicon-on-insulator substrate, which can be fabricated using deep UV photolithography. The fabricated grating coupler yields a coupling loss of -1.5 dB with 3-dB bandwidth of 54 nm at a wavelength of 1560 nm. Measurements and simulations show that the double-etched apodized grating coupler design is robust and tolerant to fabrication process variations.