title: Adiabaticity criterion and the shortest adiabatic mode transformer in a coupled-waveguide system.
abstract: By analyzing the propagating behavior of the supermodes in a coupled-waveguide system, we have derived a universal criterion for designing adiabatic mode transformers. The criterion relates epsilon, the fraction of power scattered into the unwanted mode, to waveguide design parameters and gives the shortest possible length of an adiabatic mode transformer, which is approximately 2/piepsilon1/2 times the distance of maximal power transfer between the waveguides. The results from numerical calculations based on a transfer-matrix formalism support this theory very well.
authors.affiliation: Department of Applied Physics, California Institute of Technology, Pasadena, CA 91125, USA. xksun@caltech.edu
authors.forename: Xiankai
authors.initials: X
authors.lastname: Sun
authors.forename: Hsi-Chun
authors.initials: HC
authors.lastname: Liu
authors.forename: Amnon
authors.initials: A
authors.lastname: Yariv