Design and optimization of the grating coupler in the 2  µm band

This paper mainly discusses the design and optimization of the grating coupler for the 2 µm band and selects the top layer silicon with a thickness of 0.34 µm according to the characteristics of the waveguide mode field. The TE polarization uniform grating coupler with a high coupling efficiency is achieved by scanning the etched depth and etched length, with the simulated coupling efficiency of -2.28d B. To further improve the performance, we optimize the grating coupler with the scattering strength. A TE polarization nonuniform grating coupler with a center wavelength of 2 µm is designed. The simulated coupling efficiency of the grating coupler is -1.88d B. The fabricated uniform grating coupler shows a center wavelength of 2 µm and a peak coupling efficiency of -5.07d B. The fabricated nonuniform grating coupler shows a center wavelength of 2 µm and a peak coupling efficiency of -4.1d B.