Fabrication of 2 × 2 tapered multimode interferencecoupler

Abstract
The authors demonstrate a 3 dB 2 × 2 parabolically tapered multimode interference (MMI) coupler with a large cross-section and space between the different ports using silicon-on-insulator technology. The device exhibits a uniformity of < 0.8 dB and can be used in the realisation of an MMI-based optical switch with a high extinction ratio.