Integrated multi-port circulators for unidirectional optical information transport.

On-chip photonic networks hold great promise for enabling next-generation high speed computation and communication systems. It is currently envisioned that future integrated photonic networks will be capable of processing dense digital information on a single monolithic platform by involving a multitude of optical components ranging from lasers to modulators, to routers, interconnects and detectors. Among the possible functionalities to be incorporated in such arrangements is the ability to route information in a unidirectional way among N-ports - a capability typically afforded through the use of optical circulators. Yet, in many settings, what is basically needed is re-routing information in a unidirectional fashion without necessarily invoking optical isolation. Of interest would be to devise strategies through which miniaturized optical devices can be monolithically fabricated on light-emitting semiconductors by solely relying on physical properties that are indigenous to the material itself. By exploiting the interplay between non-Hermiticity and nonlinearity, here we demonstrate a new class of chip-scale information transport devices on spatially modified III-V quantum well systems. These unidirectional structures are broadband (over 2.5 THz) at 1550 nm, effectively loss-free, color-preserving, and in proof-of-principle demonstrations have provided 23 dB isolation when used under pulsed-mode conditions at milliwatt (mW) power levels.