Efficient tapering to the fundamental quasi-TM mode in asymmetrical waveguides

Abstract

The tapering problem of the fundamental quasi-TM mode in thin asymmetrical waveguides is investigated.Mode conversions are found to be at the origin of the failing adiabatic tapers.We propose and investigate three non-adiabatic taper solutions, a focusing grating coupler, a lensed taper and a discontinuous taper, which circumvent these mode conversions.