Waveguide silicon nitride grating coupler

Grating couplers are one of the most used elements for coupling of light between optical fibers and photonic integrated components. Silicon–on–insulator platform provides strong confinement of light and allows high integration. In this work, using simulations we have designed a broadband silicon nitride surface grating coupler. The Fourier–eigenmode expansion and finite difference time domain methods are utilized in design optimization of grating coupler structure. The fully, single etch step grating coupler is based on a standard silicon–on–insulator wafer with 0.55 μm waveguide Si3N4 layer. The optimized structure at 1550 nm wavelength yields a peak coupling efficiency –2.6635 dB (54.16%) with a 1–dB bandwidth up to 80 nm. It is promising way for low-cost fabrication using complementary metal–oxide– semiconductor fabrication process.

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