Fig. 1. Structure diagram of the liquid crystal integrated metal grating (LCMG) under the constant M-field and variable E-field (B∥x, E∥z); the coordinate axis is attached to the right. The diagram of LC orientation in the LCMG when (a) E < 6 kV/m; (b) 6 kV/m < E < 20 kV/m; (c) E > 20 kV/m.

Fig. 2. (a) Experimental light path of the THz-TDS system; the sample is placed in a 3D-printed mold with a set of permanent magnets, and the E-field is applied by the connected wires. The experimentally measured (b) time-domain signals and (c) refractive index of the LC with 90° and 0° orientations under the E-field of 0 and 20 kV/m. (d) The experimental and simulative transmission of the metal grating at TM and TE polarization modes.

Fig. 3. Experimental (a) time-domain signals and (b) transmission spectra of the LCMG when the E-fields increase from 0 to 20 kV/m. (c) The diagrams of the effective refractive index (n_eff) ellipsoids of the LC with the E-field at 0–6 kV/m, 6–20 kV/m, and 20 kV/m. (d) The simulated transmittance spectra when the LC molecules are orientated with different angles to the coordinate axis.

Fig. 4. Polarization evolution in the LCMG when the LC layer is in the (a) x and (b) z orientations.

Fig. 5. Distribution of the E-vector at the (a) input plane, (b) middle plane, and (c) output plane of the x−y cutting view in the LCMG when the LC layer is in the x orientation at 0.78 THz. The arrows indicate the direction of the THz polarization. The y−z cutting plane of E-vector distributions in the LCMG when the LC layer is in the (d) x orientation or (e) z orientation.

Fig. 6. (a) Working principle diagram of the unidirectional transmission in the LCMG. (b) The extinction ratios of unidirectional transmission; the experimental and simulated data are represented by the dotted line and straight line, respectively.