Sub-Decibel Off-Chip Fiber Couplers Based on L-Shaped Waveguides and Subwavelength Grating Metamaterials

Abstract

Uniform grating couplers based on versatile L-shaped waveguides are experimentally demonstrated, with coupling loss of −2.7 dB and back-reflections of −20 dB. Apodized couplers with subwavelength-grating metamaterials predict improved fiber-chip coupling down to −0.46 dB within device layouts compatible with lithographic technologies available in nanophotonic foundries.