We present a terahertz polarization converter based on a reflective metasurface of periodically arranged asymmetric cruciform resonators. Unlike prior split-ring or fractal geometries, the cruciform architecture achieves multi-band handedness switching with reduced structural complexity and scalable fabrication. The device supports six resonant bands, delivering polarization conversion ratios above 95%, axial ratios below 3 dB, and ellipticity transitions approaching \(\pm 1\) . Left-handed circular polarization dominates across 0.47–0.83 THz, while right-handed states emerge near 1.09 and 1.32 THz, confirming dynamic handedness control. Numerical simulations performed using CST Studio Suite demonstrate that the proposed metasurface achieves stable performance under normal incidence and oblique angles up to \(20^\circ \) , with consistent response across azimuthal rotations from \(0^\circ \) to \(80^\circ \) . With a fractional bandwidth of 60.6%, the design surpasses conventional THz converters in spectral coverage and angular tolerance. By integrating broadband circularity, multi-band operation, and reconfigurable handedness control within a simple cruciform geometry, this work establishes a numerically validated design platform with clear fabrication feasibility for polarization multiplexing and adaptive modulation in terahertz communication systems.
