CMOS-compatible, broadband, and polarization-independent edge coupler for efficient chip coupling with standard single-mode fiber.

A CMOS-compatible, broadband, and polarization-independent edge coupler for efficient chip coupling with standard single-mode fiber is proposed. Three layers of a silicon nitride waveguide array with the same structures are used in the top oxide cladding of the chip to achieve high coupling efficiency and to simplify the mode transformation structure. Optimal total coupling loss at the wavelength of 1550 nm, -0.49 for TE mode polarization and -0.92 for TM mode polarization is obtained. The -1 bandwidth is beyond 160 nm for TE mode polarization and ∼130 for TM mode polarization, respectively. A significant reduction in the packaging cost of silicon photonic chips is anticipated. Meanwhile, the structure holds vast potential for on-chip three-dimensional photonic integrations or fiber-to-chip, chip-to-chip optical interconnections.