Analysis and fabrication of sub micron scale directional coupler in high-index Silicon-On-Insulator

In this paper we describe the design, fabrication and analysis of a directional coupler using sub micron SOI waveguides. Specifically, we focus on couplers featuring sub 100nm waveguide separation. Several phenomena that occur due to the ultra small gap are examined. We show that the etching rate at the waveguides gap is decreased and as a consequence the coupling between the waveguides is enhanced. Three dimensional numerical simulations are presented as well as fabrication results.