High order mode conversion via focused ion beam milled Bragg gratings in Silicon-on-Insulator Waveguides

We report the first use of focused ion beam milling to fabricate surface relief gratings in optical waveguides. We demonstrate efficient coupling to very high order modes in silicon-on-insulator waveguides and discuss the implications both for future devices based on higher order modes as well as more conventional devices based on Bragg reflection from the fundamental mode.