Asymmetric light transmission via Sb2S3-enhanced nonreciprocal gratings on glass substrate

Abstract

We propose and demonstrate a compact, high-performance optical isolator utilizing nonreciprocal gratings enhanced by antimony trisulfide (Sb2S3 ) deposited on a glass substrate. The vertical asymmetry created by the layered materials and the a-Si grating enables direction-dependent optical transmission behavior in the near-infrared spectral range. Rigorous coupled-wave analysis (RCWA) simulations reveal that the introduction of Sb2S3 significantly boosts nonreciprocal transmission contrast, enabling isolation ratios exceeding 20 dB under optimized structural parameters. Moreover, by breaking mirror symmetry, the device exhibits polarization-dependent behavior that can facilitate optical isolation. The dynamic phase transition of Sb2S3 allows the device to selectively transmit specific wavelengths. Crystallization of Sb2S3 increases both refractive-index contrast and absorption, yielding sharper resonance features and more efficient suppression of backward transmission than in the amorphous state. This work provides a promising route toward scalable, efficient, and broadband nonreciprocal photonic devices based on cost-effective and versatile material platforms.