A rib optical waveguide with cutoff mesa isolation

A rib optical waveguide using the concept of optical cutoff to provide isolation between adjacent waveguides in a photonic integrated circuit is disclosed. Due to the evanescent nature of light propagation in cutoff waveguides, this cutoff mesa rib waveguide permits fabrication of single-moded rib waveguides with minimal self-interference and crosstalk by means of light guided in a remaining slab waveguide. Design rules are given and operation of a single-moded cut-off mesa rib waveguide and an MZI using this waveguide are demonstrated.