Cladding-Free Unidirectional Waves Enabled by Artificial Gauge Fields in Tilted Grating Structures

Conventional dielectric waveguides confine electromagnetic waves through refractive index contrast between core and cladding materials, yet inherently lack nonreciprocal transmission capabilities. In this study, we demonstrate a waveguide system engineered via artificial gauge fields that achieves simultaneous optical confinement and nonreciprocal propagation without requiring additional cladding structures, thereby substantially reducing system complexity. Theoretical analysis and experimental verification reveal that directly tilted structures effectively generate gauge fields to modify dispersion relations, thereby eliminating backward propagation channels and ensuring robust unidirectional wave propagation. Our experimental results closely align with the physical model predictions, validating the accuracy of our methodology. Compared with traditional dielectric waveguides, the structural simplicity of our design significantly reduces fabrication complexity, making it particularly suitable for integrated photonic circuits and advanced optical systems. This research establishes an effective strategy for realizing unidirectional wave propagation, thus providing a novel paradigm for developing next-generation photonic devices.