Low-loss fiber-to-chip edge coupler for silicon nitride integrated circuits

作者：ZHU, X. I. A. O. T. I. A. N.; LI, G. U. A. N. G. K. U. O.; WANG, X. I. A. N. G.; LI, Y. U. H. U. A.; DAVIDSON, R. O. Y.; LITTLE, B. R. E. N. T. E.; CHU, S. A. I. T.^*

来源：Optics Express, 2023, 31(6): 10525-10532.

DOI：10.1364/OE.483907

• GRATING COUPLER
• CONVERSION
• PHOTONICS

Silicon nitride (SiN) integrated optical waveguides have found a wide range of applications due to their low loss, broad wavelength transmission band and high nonlinearity. However, the large mode mismatch between the single-mode fiber and the SiN waveguide creates a challenge of fiber coupling to these waveguides. Here, we propose a coupling approach between fiber and SiN waveguides by utilizing the high-index doped silica glass (HDSG) waveguide as the intermediary to smooth out the mode transition. We achieved fiber-to-SiN waveguide coupling efficiency of lower than 0.8 dB/facet across the full C and L bands with high fabrication and alignment tolerances.