All-dielectric metasurface achieving opposite beam deflection at dual bands

With the rapid development of spectral imaging, on-chip communication, and multifunctional integrated photonics, modern optical systems require multi-band beams to be independently controlled in three dimensions within compact platforms. However, conventional multi-band solutions typically rely on multiple optical components or complex folded beam paths, resulting in bulky structures and inter-band crosstalk that limit device integration and scalability.To address this challenge, we propose a dual-band dual-phase-gradient design strategy for independent wavefront control. This approach enables mutually independent phase-gradient units for different wavelengths to coexist on a single-layer metasurface, achieving spatially independent beam deflection. To validate the strategy, a Si/SiO₂ all-dielectric metasurface is designed for the 800 nm and 1150 nm bands.The meta-units provide full 0−2π phase coverage at their respective bands. By imposing phase gradients and arranging the two types of units in a 90° rotationally interleaved configuration, a composite periodic structure is formed in which dual-band phase profiles coexist without interference. Simulations show that under normal incidence, the device deflects the 800 nm and 1150 nm transmitted beams by approximately 14° and 24° along orthogonal transverse directions, achieving clear spatial separation and independent beam manipulation. The device also exhibits polarization-insensitive and stable wavefront control, confirming the reliability of its dual-band orthogonal operation.This design strategy provides a compact, efficient, and generalizable pathway toward highly integrated multi-band on-chip photonic devices, with broad potential applications in spectral imaging, dual-band communication, and integrated photonic systems.