Multimode Interference Couplers With Reduced Parasitic Reflections

Abstract

Parasitic reflections can deteriorate the performance of a photonic integrated circuit. This is especially true in circuits containing amplifiers, but even in passive circuits, small reflections can already have a strong influence on circuit performance. It is known that strong reflections can be present when using a 2 <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex Notation="TeX">$\,\times\,$</tex></formula> 1 multimode interference coupler (MMI) as a combiner. We investigate methods for reducing these spurious reflections in a generic integration technology. We present a novel MMI shape whose measurements show reduced reflections by 17.5 dB.