Nonreciprocal transmission based on self-induced nonlinear effects in bifacial dielectric metasurfaces

The breaking of Lorentz reciprocity law is a nontrivial task, since it usually requires bulky magnets or complicated time-modulation dynamic techniques to be accomplished. We present a simple and compact design of a nonlinear bifacial dielectric metasurface to achieve strong self-induced passive nonreciprocal transmission without the use of external biases. It is composed of two passive silicon-based metasurfaces exhibiting Fano and Lorentzian resonances embedded in an ultrathin glass substrate. Highly asymmetric field enhancement is achieved that leads to strong nonreciprocity at low excitation intensities. Moreover, a cascade design is presented to further improve the insertion loss and broaden the nonreciprocal intensity range. The proposed structure is ideal for free space optics applications, can operate under both incident polarizations, and require very low input excitation power to reach the nonreciprocal regime, which can lead to the design of new nanophotonic-based all-optical diodes, isolators, circulators, and ultrathin protective layers for sensitive optical components.