Bias-free self-induced nonreciprocal transmission based on ultrathin nonlinear dielectric metasurfaces

We demonstrate a simple bias-free self-induced nonreciprocal device of an ultrathin bifacial dielectric metasurface. It is composed of two passive silicon-based metasurfaces exhibiting Fano and Lorentzian resonances, respectively. The narrowband resonant response, as well as the boosted field enhancement, lead to very low required input intensity values to obtain significant nonreciprocal transmission. Cascaded metasurface designs are also presented to further improve the geometric asymmetry and self-induced nonreciprocal performance. This work is expected to have several applications, such as nonreciprocal ultrathin coatings for the protection of sources or other sensitive equipment from external pulsed signals, circulators, and isolators.