Fig. 1. (a) SEM image of the Si PB metasurface. Inset: geometry of the meta-atom; (b) geometry of the LC-PB metasurface; (c) optical path diagram of AR-THz-TDPS system; (d) detailed diagram of the experimental setup for time signal measurement with angle resolution and orthogonal polarization detection.

Fig. 2. Simulative transmission spectra of the four spin states (LL, RL, RR, and LR) for four meta-atoms (P1, P2, P3, and P4) with different orientations of LC molecules: (a) along the z axis and (b) y axis. The inset shows the structures of the LC-PB meta-atom in two cycles of the period. Corresponding relative phase shift spectra: (c) LC molecules along the z axis and (d) y axis. Schematic diagram of the corresponding phase gradient relation, spin states, and deflection direction of the incident wave and outgoing wave with the orientation of LC along the (e) z axis and (f) y axis.

Fig. 3. Schematic diagrams of the LC-PB metadevice in different cases: (a), (b) LCP incidence; (c), (d) RCP incidence. (a), (c) LC molecules along the y axis without EMF; (b), (d) LC molecules along the z axis with EMF. The simulated electric field distributions of the spin states at 1.0 THz are located below the corresponding diagram. The simulated diffraction efficiency map of the LC-PB metadevice varies with frequency and deflection angle when the RCP is incident: (e) LC molecules are along the y axis and (f) z axis.

Fig. 4. Experimentally measured THz response of LC without Si PB metasurface: (a) transmission spectra of linear polarization along x and y directions; (b) birefringence phase shift spectrum between x and y directions at B=0 and 60 mT. Experimentally measured intensity spectra of the four spin states through the bare PB metasurface without LC at (c) positive and (d) negative deflection angles.

Fig. 5. Experimentally measured THz intensity spectra of the four spin states through the LC-PB metadevice at different deflection angles by AR-THz-TDPS: (a) positive deflection angles at B=0  T; (b) negative deflection angles at B=0  T; (c) positive deflection angles at B=60  mT; (d) negative deflection angles at B=60  mT.

Fig. 6. Experimentally measured THz spectra of the four spin states with the EMF increasing from 0 to 60 mT at the deflection angle of ±22.5°: (a) LL state at 22.5°; (b) RL state at −22.5°; (c) LR state at 22.5°; (d) RR state at −22.5°.

Fig. 7. Experimental modulation depth of LC-PB metadevice with increasing EMF at ±22.5°: (a) LCP and (b) RCP incidence.

Fig. 8. Experimental total transmittance spectra of LCP and RCP incidences at all positive and negative deflection angles with or without EMF: (a) LCP incidence at B=0  T; (b) RCP incidence at B=0  T; (c) LCP incidence at B=60  mT; (d) RCP incidence at B=60  mT.

Fig. 9. Experimental spin isolation of LC-PB metadevice for positive and negative deflection angles at (a) B=0  T and (b) 60 mT.