ABSTRACT The anomalous transverse magneto‐optical Kerr effect (TMOKE) under s‐polarization is typically suppressed by symmetry constraints, leading to negligible signals. Here, we propose an indirect magneto‐optical (MO) coupling mechanism that originates from the spatially asymmetric near‐field distribution of resonant modes, rather than from the direct coupling between the incident field and the MO tensor. Guided by this principle, we design a quasi‐two‐dimensional MO grating that strategically coordinates resonances along two orthogonal directions. Specifically, modes perpendicular to the grating ridges establish a wide‐angle broadband near‐zero reflection background to satisfy the rigorous mathematical condition for maximum TMOKE, whereas the orthogonal high‐Q resonances are responsible for inducing maximal near‐field asymmetry. This allows us to push the s‐polarized TMOKE to approach its theoretical limit (∼2)—a performance leap of over an order of magnitude compared to previous reports. The proposed structure exhibits exceptional robustness against material losses and fabrication tolerances, alongside a broad angular tolerance (up to 40°), offering a practical blueprint for high‐performance nonreciprocal photonic devices.
Yang et al. (Thu,) studied this question.