Integrated optically isolated laser source via non-reciprocal counter-propapagating four-wave mixing

Optical isolators based on non-reciprocal optical elements are crucial to protect laser sources from unwanted back-reflections. Commercial optical isolators are built using bulk components and micro-optics technology, and contribute a large fraction of the overall manufacturing cost of a telecom laser. Despite the impressive development in photonic integration techniques, the integration of non-reciprocal elements within conventional optoelectronic platforms, such as III-V semiconductors, is still a major challenge. So far, only a few schemes for integrated optical isolators have been actually fabricated and tested, including hybrid integration of magneto-optical materials [1], non-reciprocal mode conversion and non-reciprocal phase shift, high-speed cascaded phase-modulation [2]. Each of the above solutions has specific drawbacks, such as large insertion loss, low isolation, large size.