High-fidelity stimulated Raman adiabatic passage analog in optimum three-waveguide system

We extend Dykhne-Davis-Pechukas (DDP) approximation which describes the nonadiabatic transition probability of a two-state atom system to a three-waveguide coupler. We optimize the traditional Gaussian tunneling rate distributions of optical waveguides based on the parallel adiabatic passage (PLAP) technique which originates from the DDP scheme. The tunneling efficiency can be further improved. We explore the robustness and the tunneling transfer error of the stimulated Raman adiabatic passage (STIRAP) in optical waveguides. The results show that the DDP-optimized scheme can keep the robustness against variations in the shift of propagation constant and hence the width of the channels.