3D SOI edge coupler design for high tolerance

We designed and manufactured two single-mode fiber-to-chip three-dimensional (3D) edge couplers with taper and semi-cone structures on a 3.5 µm silicon device layer of a silicon-on-insulator. The 3D finite-difference time-domain is used to simulate and optimize the structure of the edge couplers within the 1550 nm band. The simulation results reveal a maximum coupling efficiency of the 3D edge couplers above 91.42% for the TE mode. The 3 dB coupling tolerances of the TE mode in horizontal and vertical directions are ±4.5 and ±1.5 µm, respectively. Laser-direct-writing grayscale lithography and inductive coupled plasma-reactive ion etching are used in the fabrication of 3D edge couplers. Experimental data show that 3D couplers have a maximum coupling efficiency of about 83.41% in the TE mode.