Terahertz Bidirectional Non‐Reciprocal Transmission Based on Nonlinear Chiral Metasurfaces

Non‐reciprocal transmission is the core function of terahertz isolators, and nonlinearity‐induced non‐reciprocal metasurfaces make compact non‐reciprocal devices feasible. This paper proposes an As 2 Se 3 dielectric nonlinear chiral metasurface, which achieves non‐reciprocal transmission of terahertz waves by generating quasi‐bound states in the continuum (QBICs) through rotational symmetry breaking of the metasurface structure. The resonance mechanisms of the QBICs are analyzed using multipole decomposition, and the influence of structural parameter variations on the non‐reciprocal transmission characteristics of terahertz waves is investigated. At an incident terahertz wave intensity of 1.401 MW/cm 2 , the nonlinear chiral metasurface achieves a forward isolation of 64.8 dB and an insertion loss of 3.01 dB. At an incident intensity of 1.51 MW/cm 2 , the backward isolation reaches 12.12 dB with an insertion loss of 3.32 dB. These results demonstrate that the designed metasurface enables bidirectional non‐reciprocal transmission of terahertz waves under dual‐QBIC resonance modes, showing broad application potential in non‐reciprocal devices and nonlinear optics.