This paper aims to design a novel polarization-transforming metasurface for terahertz wavefront control. The design successfully achieves polarization conversion functionality and effectively reduces broadband radar cross section in the terahertz band, representing significant advancement in electromagnetic wave manipulation. The proposed design establishes an efficient approach for terahertz wavefront control while demonstrating the capabilities of encoded metasurface technology in electromagnetic wave regulation. In radar stealth applications, reducing radar scattering cross-sectional area remains a critical research focus with substantial practical value. This research presents both scientific innovation and practical applicability. Through comprehensive comparison with existing literature, this study demonstrates the superior characteristics of the designed polarization conversion metasurface. The design excels in several key performance metrics, including design simplicity, broadband performance, RCS reduction effectiveness, and wide-angle stability. These advantages provide valuable reference for academic research and introduce novel methodologies for related fields. This research advances terahertz wavefront control technology and radar stealth technology by enhancing and complementing existing techniques.

The research methodology encompasses the design and optimization of polarization-conversion metasurface units and the implementation of intelligent algorithms for optimal array configuration. The study initially proposes a polarization-conversion metasurface element structure for the terahertz band. The structure incorporates 2-bit supercells with digital encoding, based on the PB geometric phase principle. The genetic algorithm, an intelligent optimization approach that emulates natural biological evolution, identifies optimal solutions through natural selection mechanisms. The study achieves significant radar cross section reduction through scattering function design, fitness function implementation, and array layout optimization using genetic algorithms. This approach attains unit polarization conversion efficiency exceeding 0.9 across a broad frequency range. The array demonstrates radar cross section reduction greater than 10 dB across multiple frequency bands, maintaining stable performance over wide angles. For experimental validation, initial theoretical calculations utilize MATLAB’s mathematical computation capabilities to analyze the designed metasurface elements and arrays. Subsequently, CST simulation tools provide detailed electromagnetic simulation of wave-metasurface interactions. The dual verification through MATLAB and CST ensures consistency and accuracy between theoretical calculations and simulation results.

The study presents a novel polarization-converted metasurface element characterized by simplicity, efficiency, and flexibility (Fig. 1). Experimental analysis of the progressively improved structure examines the R_yy values at each structural stage (Fig. 2). Resonant current analysis occurs at three resonant points (Fig. 3). Simulation yields reflection coefficients for same polarization and cross polarization, and polarization conversion efficiency at varying angles (Fig. 4). uv coordinate system simulations provide reflection amplitude and phase of copolarization reflection coefficient (Fig. 5 and Fig. 6). Component rotation angle modifications regulate electromagnetic wave phase (Fig. 7). The design includes four types of 2-bit encoded super units (Fig. 8). Optimization algorithms determine optimal arrangement and electric field characteristics (Fig. 9). Simulations examine scattering beams of different polarized waves under normal incidence and scattering characteristics of xoz surface array and metal plate (Fig. 10 and Fig. 11). RCS reduction exceeds 10 dB for different polarization waves under normal incidence within 0.695?0.846 THz, 0.872?1.195 THz and 1.476?1.674 THz, reaching maximum reduction of 32 dB at 1.05 THz, demonstrating effective RCS reduction (Fig.12). For X-polarized wave incidence angles from 0° to 30°, RCS decreases exceed 8.0 dB within 0.661?1.312 THz. For Y-polarized waves, RCS reduction exceeds 8.0 dB within 0.683?0.849 THz, 0.851?1.275 THz and 1.500?1.687 THz, indicating effective scattering control for oblique incidence from 0° to 30°. However, larger incidence angles diminish RCS reduction effectiveness (Fig.13). Analysis includes scattering beams of linearly polarized waves at 30°, 0.8 THz (Fig.14).

This study introduces a novel terahertz wideband polarization conversion metasurface structure and validates its practical applications through theoretical analysis and simulation experiments. The device demonstrates both linear polarization conversion capabilities and scattering control characteristics. The findings indicate that the polarization converter achieves conversion efficiency exceeding 0.9 for electromagnetic waves at normal incidence within the THz frequency bands of 0.706?0.862 THz and 0.911?1.744 THz. For electromagnetic waves at oblique incidence angles of 0°?40° within the THz frequency bands of 0.692?0.836 THz and 0.873?1.427 THz, the polarization conversion efficiency surpasses 0.7. The proposed structure exhibits enhanced performance in bandwidth, efficiency, and adaptability to small angles. Furthermore, utilizing the PB phase principle and incorporating phase gradient, effective wideband phase modulation has been achieved. The structure demonstrates RCS reduction exceeding 10 dB at normal incidence across multiple frequency bands, and greater than 8 dB reduction for oblique incidence angles from 0° to 30°. These results represent significant improvements over current polarization conversion metasurfaces in terms of RCS reduction and bandwidth limitations. The research advances existing technologies through enhanced wideband characteristics, conversion efficiency, and radar cross section reduction capabilities.