Frequency-reconfigurable polarization conversion technology with one-octave band separation and consistent chirality

A dual-wideband linear-to-circular (LC) polarization converter with a one-octave band separation (OBS) working mode based on liquid crystal regulation is proposed in this paper. OBS polarization conversion refers to dual-band polarization conversion where the second operating band either completely covers twice the range of the first band or corresponds exactly to twice the frequency range of the first band. The performance of the design, both before and after optimization, is analyzed in detail. The optimization process achieves the desired outcome by introducing cavities into the liquid crystal layer of the initial structure. At zero bias, the optimized structure achieves LC conversion at 0.779–0.976 and 1.429–2.085 THz, with relative bandwidths of 22.45% and 37.34%, respectively. The generated circularly polarized (CP) waves are all right-handed. When the liquid crystal is fully biased, the operating frequency bands shift to 0.758–0.978 and 1.504–2.154 THz, with relative bandwidths of 25.35% and 35.54%, respectively, and the CP waves are all left-handed. The OBS frequency bands for the two typical bias states are 1.558–1.952 and 1.516–1.956 THz, respectively. These bands are fully covered by their respective second operating ranges, enabling the OBS polarization conversion working mode. LC conversion with the same CP wave chirality in dual-wideband operation is achieved through an innovative and advanced design in this paper. Furthermore, it addresses the common issue of high-frequency bandwidth attenuation in dual-band polarization converter designs. Liquid crystals also offer flexible, frequency-reconfigurable operation, a feature not found in conventional designs. The OBS working mode, with the same CP wave chirality, creates a synergistic relationship between operating bands, opening up broad application prospects in advanced high-speed communications, encryption, integration with nonlinear devices, and molecular detection.