Bidirectional nonreciprocal transmission in a silicon metasurface with high- <i>Q</i> guided-mode resonances

Nonreciprocal transport is indispensable for many modern optical devices. However, traditional nonreciprocal devices heavily depend on external bias. Achieving significant nonreciprocity in practice remains challenging. In this work, we propose a Kerr-nonlinearity-based design to achieve strong nonreciprocal transmission. By leveraging high-<i>Q</i> guided-mode resonances (GMRs) in a Si waveguide nanostructure decorated with periodic grooves, we demonstrate magnetic-free bidirectional nonreciprocal transmission and isolation. A large nonreciprocal intensity range (NRIR ≈ 3.7) is achieved through parameter tuning under the low pump intensity. Simultaneously, high-performance bidirectional isolation behaviors are realized including an isolation of 71.16 dB with 2.59 dB insertion loss for forward transmission and an isolation of 80.98 dB with 1.62 dB insertion loss for reverse transmission. This design offers a versatility for applications in optical communication, optical switches, and bidirectional nonreciprocal devices.