Fig. 1. Normalized phase diagrams of (a) a vortex plate with m=2, (b) a circular grating with Λ=1728μm, and (c) their integration. (d) Photo of the fabricated LC sample under crossed polarizers (indicated by two orange arrows). Scale bar: 1 mm.

Fig. 2. (a) Simulated normalized THz intensity distribution in the xz plane at 1.2 THz. The white dashed lines indicate z=5 and 20 mm. Simulated THz intensity and phase distributions at 1.2 THz in the xy plane at (b) z=5mm and (c) z=20mm, respectively.

Fig. 3. (a) Measured THz intensity distributions in the xz plane at 1.2 THz. The white dashed lines indicate z=5, 10, 15, and 20 mm, separately. (b)–(e) Measured THz intensity and phase distributions at 1.2 THz in the xy-plane at (b) z=5mm, (c) z=10mm, (d) z=15mm, and (e) z=20mm, respectively. (f) Normalized intensity profiles along the x and y axes labeled by the dashed lines in (b). (g) Dependency of PCR on frequency.

Fig. 4. Measured THz intensity distributions in the xz plane at (a) 1.1 THz and (b) 1.4 THz. The white dashed lines in (a) and (b) indicate z=10mm. THz intensity and phase distributions in the xy plane at (c) 1.1 THz and (d) 1.4 THz.