Analysis of the coupling characteristics of a tapered three-guide coupled system

Optical coupling characteristics of a three-guide coupled system are discussed. Application of a taper-formed waveguide in the system is proposed. A theoretical analysis of the tapered waveguide system is presented by applying a modified coupled-mode theory, with the tapered guide being approximated by successive stepped small guide segments. Based on numerical examinations, particular coupling characteristics of the tapered guide system are demonstrated. An application of the tapered three-guide coupled system in a type of optical isolator is proposed. The main working principles of the isolator are presented. >