Fig. 1. Schematic diagram of an HMM Airy beam generator, where the HMM meta-atom is presented in the top right corner. The thicknesses of the metal and dielectric layers are denoted by t_m and t_d, respectively. The widths of long- and short-edges of HMM are denoted by W_l and W_s, respectively. The angle between the l axis and the x axis is the orientation angle θ. LCP plane waves normally illuminate the HMM Airy beam generator from the left-hand side.

Fig. 2. (a) The dispersion relations of l- and s-polarized fundamental SW modes for RHMM with different W_l. (b) The birefringent index between l- and s-polarized fundamental SW modes as a function of W_l at 8.6 GHz. RHMM meta-atom is made up of multilayered copper (conductivity of 5.8× 10⁷ Ω⁻¹ ⋅ m⁻¹ and thickness of t_m = 0.068 mm) and FR4 (relative permittivity of 4.3+0.025j and thickness of t_d = 0.45 mm).

Fig. 3. The amplitude (red line) and propagation phase (blue line) of the transmitted RCP electric field as a function of W_l upon LCP incidences at 8.6 GHz. The introduced PB phase [green line in (a) and purple line in (b)] causes the transmission phase of RCP to be zero [parallel dashed lines in (a)], and to be π [parallel dashed lines in (b)]. 32 pairs of copper/FR4 layers and 2 mm thick FR4 substrate are used for the RHMM meta-atom, while the other geometrical parameters are the same as those in Fig. 2.

Fig. 4. Design and verification of the HMM Airy beam generator. (a) Airy beam profile: red line for the field envelop of Airy beam extracted by Eq. (6) and blue dots for sampling points. (b) W_l and θ as a function of the serial number of the RHMM unit. (c) A part of the fabricated sample. (d), (e) The electric field intensity distributions of the transmitted RCP waves obtained by FDTD simulation (d), and by near-field scanning experiment (e) at 8.6 GHz.

Fig. 5. The measured electric field intensity distributions of the transmitted RCP around the pre-design frequency of 8.6 GHz: (a) 8.4 GHz, (b) 8.5 GHz, (c) 8.7 GHz, and (d) 8.8 GHz.

Fig. 6. Numerical demonstration of an HMM Airy beam generator in the near-infrared range. (a) The amplitude (red line) and propagation phase (blue line) of the transmitted RCP electric field as a function of W_l. The introduced PB phases, denoted as green and purple lines, cause the transmission phase of RCP to be zero and π, respectively. (b) W_l and θ as a function of the serial number of the RHMM unit. (c) The electric field intensity distribution of the transmitted RCP waves under LCP incidence at 1.55 μm.