Nanoscale plasmonic circulator

Breaking time reversal symmetry of the light flow, implying optical wave isolation and directional light guiding, is crucial for signal handling and integrated optics. Such signal isolation is possible with an optical circulator-a three-port magneto-active nonreciprocal device, which transmits light from any of its input ports into the next port in a circular order, isolating the remaining port. Small magneto-optical activity at optical frequencies challenges the miniaturization and further on-chip integration of this key fundamental component. Here we demonstrate theoretically that by employing principles of plasmonic mode engineering it is possible to enhance significantly magnetooptical response in a deep subwavelength regime and suggest a conceptual approach for a design of an ultracompact nanoscale passive optical circulator. This work paves the way for future generation of nonreciprocal integrated optics with a nanoscale on-chip compatibility.