Fig. 1. Terahertz polarization conversion system and measurement results of the initial terahertz signal. (a) Three-dimensional picture of the terahertz polarization conversion waveguide and the terahertz transmission/reception ends; (b) overall schematic diagram of the experimental setup; (c) time-domain plot of the initial terahertz signal; (d) frequency spectrum plot of the initial terahertz signal; (e) polarization plot of the initial terahertz signal

Fig. 2. Experimental setup picture (magnetic field applied to the tail section of the waveguide)

Fig. 3. Experimental results of terahertz transmission in octagonal paper tube waveguide. (a) Terahertz time-domain waveform output from the octagonal paper tube waveguide; (b) frequency domain plot of the terahertz signal output from the octagonal paper tube waveguide; (c) transmission loss of the terahertz wave; (d) schematic diagram of the deformation of one end of the octagonal paper tube when subjected to external pressure, resulting in an increase in the horizontal inner diameter and a decrease in the vertical inner diameter; (e) time-domain shift of the horizontal terahertz component due to changes in the inner diameter; (f) time-domain shift of the vertical terahertz component due to changes in the inner diameter

Fig. 4. THz mode (0.3 Hz) patterns output from the waveguide. (a) Inner diameter of 12 mm; (b) inner diameter of 10 mm

Fig. 5. Octagonal terahertz polarization converter based on magnetically actuated origami and the experimental results. (a) Octagonal terahertz polarization converter based on magnetically actuated origami, with structural parameters in millimeters; (b) changes in the inner diameter of the output end of the polarization conversion waveguide under the influence of a magnetic field; (c) trend plot of horizontal and vertical inner diameters varying with increasing magnetic induction intensity; (d) evolution of the terahertz polarization state output by the polarization conversion waveguide under the action of magnetic force: linear polarization to elliptical polarization to circular polarization

Fig. 6. Magnetically controlled terahertz polarization converter based on U-shaped waveguide and the experimental results. (a) Magnetically controlled terahertz polarization converter based on U-shaped waveguide, with structural parameters in millimeters; (b) changes in the inner diameter of the output end of the polarization conversion waveguide under the influence of a magnetic field; (c) trend plot of the vertical inner diameter varying with increasing magnetic induction intensity; (d) evolution of the terahertz polarization state output by the polarization conversion waveguide under the action of magnetic force: left-handed elliptical polarization to linear polarization to right-handed elliptical polarization

Fig. 7. THz signals detected using a non-magnetic waveguide are essentially identical with and without the presence of a magnetic field. (a) THz time-domain waveforms; (b) THz spectra