Design and simulation of a fiber to chip coupler designed on SOI platform with subwavelength grating

Abstract

ABSTRACT We report on a design for integrated surface diffraction grating fiber to chip coupler designed on Silicon-on-insulator platform with subwavelength grating, which is compatible with 193 nm laser DUV lithography. Surface diffraction grating couplers are perspective coupling solution, which extr acts light from the Silicon-on-insulator wire waveguide and emits it towards an optical fiber placed over the SOI chip 1 . However, they are polarization and spectral sensitive. Efficient grating-to-fiber coupling requires matching the grating radiated field profile and the optical fiber mode. The aim of this design is the reducing back reflection of the fiber to chip coupler by using subwavelength grating for continuously tuning effective refractive index and tune the profile of diffracted power. The structure of designed fiber to chip coupler consists of relatively large tapered segment which adjusts cross-section of SOI wire waveguide to standard single mode fiber diameter and surface diffraction grating for verti cal coupling to the fiber. The simulation of the fiber to chip coupler is performed by FDTD tool and BPM tool. The effective refractive index is tuned over diffraction grating by adjusting the duty cycle of the silicon in subwavelength grating inside the surface diffraction grating. Keywords: fiber to chip coupler, surface di ffraction grating, sub-wavelength grating, silicon on isolator