Transverse multimode evolution in optical micro/nanofiber tapers

The mode conversions of micro/nanofiber (MNF) tapers are numerically simulated by using 3-Dimension Finite-Difference Beam Propagation Method(FD-BPM). We consider the behaviors of adiabatic MNF tapers and discussed that the non-adiabatic MNF taper behaves more complex multimode interference and beat effects in the transition and waist sections.