Silicon-based waveguide grating coupler

Abstract

paper we design a vertical waveguide grating coupler based on sub-wavelength grating with highly integration, high coupling efficiency and large bandwidth. A grating always shows multiple diffraction orders with different efficiency, but only a certain diffraction order with high efficiency is very effective for light coupling. The silicon-based waveguide grating is designed and simulated in this paper, which is modelled by using the Finite-difference time-domain (FDTD) method. The coupling efficiency is analyzed and optimized with the structure parameters of the grating period, duty cycle and etching depth et al. The results show that more than 30% of the coupling efficiency is obtained during the optical communication C-band (1530nm-1565nm) and remained more than 50% in the range of 1545nm-1555nm. The parameter tolerance is relatively high with more than 40nm in grating period, more than 100nm in grating etching depth and more than 140nm in grating duty cycle. Such an optical waveguide grating coupler is expected to be used for input and output of optical signal coupling in the field of silicon photonic integrated devices.