Matched MFD for fiber-to-vertical nanoslot waveguide couplers

The design of fiber-to-nanoslot waveguide low coupling loss is proposed and demonstrated. The light from fiber is coupled into the fiber-adapted waveguide based on an inverted taper structure with matching mode size. The parameters of taper tip width and taper length have been evaluated by means of overlap integral and 3D-FIMMPROP simulations at λ=1550 nm. Slightly larger fiber MFD of 2.9 μm found to be good match and achieved total coupling efficiency of 93% for an inverted taper tip width of 60 nm and length of 50 in TE polarized