Terahertz waves exhibit significant application value in fields such as substance identification, non-destructive testing, and high-speed communication due to their unique spectral characteristics and penetration capabilities. However, traditional terahertz polarization converters suffer from issues including fixed operating frequency bands and low modulation efficiency. To address these issues, a tunable terahertz cross-polarization converter based on a vanadium dioxide (VO2) composite meta-surface is proposed. A composite structure of “工”-shaped aluminum patches and VO2 sheets is employed, incorporating with a polyimide (PI) dielectric layer and an aluminum reflective backplane. By utilizing the conductivity transition property of VO2 during phase transition at 68 ℃, dynamic control over the polarization conversion performance of terahertz waves is achieved. Electromagnetic simulation results show that when VO2 is in an insulating state at room temperature, the device achieves cross-polarization conversion within the 1.31-2.15 THz frequency band. After heating above the phase transition temperature, VO2 transforms into a metallic state, at which point the operating frequency band can be flexibly tuned to 1.40-2.10 THz. Meanwhile, within the 1.50-2.00 THz frequency band, the polarization conversion ratio is higher than 99%, demonstrating excellent conversion performance.Further studies reveal that a good balance between broadband characteristics and high conversion efficiency is obtained by optimizing the dielectric layer thickness to 19 μm. Additionally, the PCR absolute fluctuation of the device is basically less than 5% within the oblique incident angle range of 0-20°, indicating good engineering adaptability. This polarization converter features a simple structure, ease of fabrication, and flexible regulation of the polarization conversion operating frequency band, holding broad application prospects in terahertz wave communication, imaging, and other related fields.
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