A novel coupler with high mode conversion efficiency for SMF and SOI single-mode waveguide coupling interface

A multilayer mode converter (MMC) with large alignment tolerance and broadband operation as well as temperature independence is designed and fabricated to alienate the mode coupling loss between a standard single-mode fiber (SMF) and a 3-D SOI rib-type waveguide. Numerical results based on semi-vectorial beam propagation method are evaluated. This presented design has achieved about 75% coupling efficiency under the consideration of all coupling losses and transition ratio at the total length 2000um.