Efficient adiabatic silicon-on-insulator waveguide taper

A silicon-on-insulator-based adiabatic waveguide taper with a high coupling efficiency and small footprint is presented. The taper was designed to reduce the incidence of mode conversion to higher-order and radiation modes inside the waveguide. In connecting a 0.5-mu m-wide output waveguide and a 12-mu m-wide input waveguide of a grating coupler, a compact 120-mu m-long taper was demonstrated, achieving a transmission of 98.3%. Previously, this transmission level could only be achieved using a conventional linear taper with a length of more than 300 mu m. (C) 2014 Chinese Laser Press