Numerical method for designing ultrashort and efficient adiabatic mode converters

Abstract

This paper proposes a fully numerical method for designing adiabatic mode converters (NM-AMCs). The proposed method can help compute efficient adiabatic guided-wave shapes for mode converters using a nonuniform section division technique. Such a scheme reduces the memory requirement and computational time for the design of adiabatic devices. Furthermore, the adiabatic mode converter comprises a ridge waveguide, which is difficult to design using analytical methods. This complex case of an adiabatic mode converter is used to demonstrate how the proposed method can readily generate a guided-wave shape that gives the same mode-connection power transfer with a far shorter length compared with a linear-shape converter. The efficiency of the device designed using this NM-AMC is significantly better than that of linear-shape converters; this designed adiabatic mode converter can enable a broad operating bandwidth. Moreover, the efficiency of the adiabatic mode converter that was designed using the NM-AMC method considerably exceeds that obtained using an analytical method proposed for a strip waveguide.