Coupling performance enhancement using SOI grating coupler design

Grating couplers are one of the most significant elements for the coupling of light between optical fibers and photonic integrated circuits. In this paper, we present the design, fabrication and experimental characterization of Silicon on Insulator (SOI) based grating couplers. The mode matching of diffracted optical field from the grating coupler with a single mode fiber at different angles is investigated here with normal surface physical contact (PC) and angled physical contact (APC) fibers. According to our simulations, the 1°tilt in the fiber angle approximately changes the position of the optimum mode coupling for the grating coupler with the single mode fiber by ∼300 nm distance. The variation of input wavelength at different grating periods gives the different optimal coupling angles for the PC fibers. The experimental results also demonstrate the coupling efficiency as −3.6 dB at 1550 nm with a simulated 3-dB bandwidth of 48 nm near the telecommunication C-band.