Fig. 1. Schematic of the experimental setup. GT prism, Glan–Taylor prism; HWP1, HWP2, and HWP3, half-wave plates; QWP1, QWP2, and QWP3, quarter-wave plates; PBS, polarized beam splitter; NFG, nonlinear fork grating; M1, M2, and M3, mirrors; CCD, charge-coupled device. Inset shows the microscope image of fork grating etched on the LN surface.

Fig. 2. Stokes parameters of SH vectorial light field. (a1)–(a4), (c1)–(c4), and (e1)–(e4), respectively, represent the simulated Stokes parameters S0, S1, S2, and S3 with the topological charge of ℓ=1, 2, 3. The corresponding experimental results are shown in (b1)–(b4), (d1)–(d4), and (f1)–(f4).

Fig. 3. First, third, fifth rows and second, fourth, sixth rows, respectively, show the results of the SH vector beams with the topological charge ℓ=1, 2, 3 when 2α+Δ12−π2=π3 and 2α+Δ12−π2=π2. Results from the second to seventh columns are intensity profiles of the generated vector beams when the polarizer has different polarization angles (0°, 30°, 60°, 90°, 120°, 150°) with respect to the positive horizontal direction. The corresponding simulated polarization distributions are displayed in (a)–(f). The arrows indicate the polarization direction of the polarizer.

Fig. 4. Experimental results corresponding to the cases of Fig. 3. The arrows indicate the polarization direction of the polarizer.

Fig. 5. Variation of generated SH vector beams power (P2) as the incident FF beams power (P1) increases before Sagnac loop. (a) ℓ=1, (b) ℓ=2, (c) ℓ=3.