Physics-driven free-form perfect reflective metadevices design

Traditional reflective metasurface devices are constrained by the grating equation, making it difficult to achieve high-efficiency arbitrary deflection angles due to their fixed unit cell periodicity. This study overcomes this limitation by introducing a physics-driven topology optimization method for rapid design. The method designs a composite reflective structure: a standard Bragg mirror provides near-perfect (>99%) reflectivity, while a topology-optimized free-form metasurface nanostructure controls the phase profile of the reflected wave. Targeting reflection angles between 25° and 85° at a wavelength of 1550nm, an iterative topology optimization process combined with electromagnetic simulation (RCWA,Rigorous Coupled-Wave Analysis) refines the topological structure of the metasurface. This design utilizes electromagnetic coupling effects to achieve the required phase distribution. Crucially, the resulting design significantly decouples performance from the constraints of unit cell periodicity. Simulations verify reflection efficiencies exceeding 90% for all target angles, with a remarkable peak efficiency of 99% achieved for 30° deflection at 1550nm. This represents a substantial performance improvement over traditional periodic cell designs. The topology-optimized reflective metasurface offers broadband high performance in the near-infrared spectrum, exhibits large angular tolerance, and maintains low cross-talk. This efficient design methodology circumvents the inherent limitations of periodic structures, enabling the creation of high-performance reflective devices with customized deflection angles. Its rapid and efficient nature holds significant promise for applications in reconfigurable photonics, compact laser systems, quantum optical control, and high-speed LiDAR.