2D spot size converter using a multilevel asymmetric coupler MAC structure for Si photonics planar technology

Abstract

In this work, we present an architecture for the design of an integrated optical spot size converter using planar technology. The proposed architecture is based on the use of multilevel planar structures without using vertical tapers. The function of the vertical taper is replaced by a horizontal taper and a multilevel asymmetric coupler structure. The proposed technique, used to couple a single-mode fiber with a core diameter of 8.2 µm to a silica-over-silicon waveguide with a 2 µ m × 4 µ m cross section, has a coupling efficiency greater than 98% without the need for a vertical coupler. The coupling transformation of the spot of the standard 500 n m × 220 n m Si photonics waveguide to the fundamental mode of a 1 µ m × 1 µ m waveguide is also demonstrated with a coupling efficiency greater than 92%. This technique offers very high flexibility in the coupling between different waveguides with different cross sections.