Hybrid-integrated optical isolators and circulators

Abstract

Magneto-optics is an area that is uniquely enabling for the production of non-reciprocal components such as optical isolators and circulators. The concepts behind the non-reciprocity include nonreciprocal polarization rotation (Faraday rotation) and nonreciprocal phase shift. A magneto-optic material that is magnetized in the direction of propagation of light acts as a Faraday rotator. An asymmetric magneto-optic waveguide that is magnetized perpendicular to the propagation direction acts as a nonreciprocal phase shifter. Both effects can be utilized to realize nonreciprocal devices. Today, commercial isolators and circulators are strictly bulk components, and as such they constitute the only type of optical component that is not available in integrated form. However, the technology for integrated nonreciprocal devices has been maturing and is expected to have a considerable impact in the communication industry by enabling the integration of complete optical subsystems. We report on the development of integrated optical isolators and circulators that consist of polymer-based planar interferometers with inserted thin films of cerium-substituted Yttrium Iron Garnet (Ce-YIG) for efficient Faraday rotation, and thin films of LiNbO 3 for wave-retarders that enable polarization-independent operation.