Fig. 1. (a) Structure of the AZO unit cell. (b) The longitudinal cross-section of the AZO unit cell with a height of H. (c) The transverse section of the AZO unit cell, where L and W represent the length and width of AZO nanorod, and I_x, I_y represent the length and width of ITO substrate. (d) Crystal axes (fast axis and low axis) coincide with E_x and E_y of the incident wave. (e) The AZO nanorod rotated by θ. (f) AZO refractive index n, k diagram.

Fig. 2. Polarization efficiency of the three structures, the incident light with left/right circled polarization and the transmission light with right/light circled polarization.

Fig. 3. Polarization conversion efficiency versus wavelength for different AZO plates: (a) AZO plates with different width W; (b) AZO plates with different length L; (c), (d) substrates with different length I_x and width I_y, respectively.

Fig. 4. (a) Schematic of polarity flip. (b)–(d) The relationship between the additional phase φ of the transmission field and the θ angle for samples S1 (450 nm), S2 (530 nm), and S3 (650 nm), respectively.

Fig. 5. Schematic of metalens designed according to PB phase method: (a) 1-D metalens, (b), (c) 2-D metalens.

Fig. 6. The phase profiles of E_x and E_y for the three structures: (a) S1 (450 nm), (b) S2 (530 nm), (c) S3 (650 nm), where the left picture in (a)–(c) is corresponding to the one without AZO. At z = 4 μm, the retardation phase curves of E_x, E_y and their differences for (d) S1 (450 nm), (e) S2 (530 nm), (f) S3 (650 nm).

Fig. 7. The 1-D AZO metalens designed based on Fig. 3(a) with a total transverse length of 20 μm, with a circularly polarized incident light. (a)–(c) The diagram of power distribution in the x–z plane for the S1 (450 nm), S2 (530 nm), and S3 (650 nm), respectively. (d)–(f) Normalized intensity diagrams based on the three images at z = 10 μm. (g)–(i) x–z plane phase profile diagram at y = 0 μm in the x–z plane.

Fig. 8. The intensity distribution on x–z plane of 2-D metalens: (a) S1 (450 nm), (b) S2 (530 nm), (c) S3 (650 nm), the z coordinates of two focal points are marked on the graph. (d)–(i) The x–y section of intensity distribution diagram at corresponding z values (marked in the upper right corner).

Fig. 9. (a)–(f) The normalized intensity diagram on the x-y plane at different z values corresponding to the six focal points in Figs. 8(d)–8(i).

Fig. 10. The x–z cross-section intensity distribution of 2D-metalens with the S3 structure of AZO nanorods by the PB phase method: (a) 60 × 60 AZO nanorods, (b) 40 × 40 AZO nanorods.

Table 1. Structure parameters of S1, S2, and S3.

Table 2. Phase shift of E_x and E_y for linearly polarized incident light at 450 nm, 530 nm, and 650 nm with respect to Figs. 6(d)–6(f).

Table 3. Focusing efficiency (FE) and NA of 2D-metalen with structures (S1, S2, S3) designed by PB phase method.