@article{wan2017circular,
  title={Circular waveguide grating-via-grating for interlayer coupling},
  author={Wan, Congshan and Gaylord, Thomas K and Bakir, Muhannad S},
  journal={IEEE Photonics Technology Letters},
  volume={29},
  number={21},
  pages={1776--1779},
  year={2017},
  publisher={IEEE}
}