Fig. 1. Schematics of vectorial meta-holograms and its design process. (a) Shining a metasurface composed of single-structure metaatom arrays with tailored wave-scattering properties (including reflection phases and polarization-coversion capabilities) by an incident light with certain polarization, a vectorial holographic image can be generated in the far field exhibiting inhomogeneous distributions of both intensity and polarization. (b) Flow chart of the design process: (1) for a holographic image with intensity and polarization distributions given by Atarh(k→) and |σtarh(k→)⟩, one can employ the generalized GS algorithm to retrieve the phase distributions of two planar sources for two circular-polarization channels; (2) linear superposition of two planar sources Φ±m(r→) yields the final near-field source, which further helps us sort out meta-atoms located at different positions with arbitrarily given incident polarization. The superscript h indicates the far-filed holographic plane, and m indicates the near-field metasurface plane.

Fig. 2. Designs and characterizations of meta-atoms. (a) Resonance phase ΦRes and (b) cross-polarization phase difference ΔΦ of MIM metaatom arrays (see inset for the structure of a typical metaatom) with different Lu and Lv, calculated by FDTD simulations at 1064 nm. Other geometric parameters of the MIM meta-atoms are fixed as: hStr=30nm, hIns=125nm, hSub=125nm, w=80nm, and Px=Py=600nm. Dashed lines denote the ΔΦ=±π contours, with Nos. 1, 2, and 3 labeling three typical meta-atoms functioning as quarter, half, and 2/3 waveplates, which are experimentally characterized. Measured polarization-filtered intensity patterns of (c) incident light with E polarized along the 45-deg angle in-between u and v axes, and light beams reflected by metasurfaces composed by meta-atoms labelled with (d) No. 1, (e) No. 2, and (f) No. 3, respectively. The working wavelength is 1064 nm. Solid lines in panels (d)–(f) are FDTD calculated results.

Fig. 3. Design of meta-holograms for achieving identical vectorial images under excitations of incident light with distinct polarizations. (a) Three incident polarizations |σ0⟩ with {Θ0=π4,π2,13π20;Ψ0=0} selected in the designs, as marked by red stars on Poincaré’s sphere. (b) The target holographic image contains 9 parts exhibiting different polarizations indicated by green segments (representing linear polarization) and red/blue circles (representing left/right circular polarizations). Top-view structures of three meta-holograms designed under incident polarizations with (c) Θ0=π4, (e) Θ0=π2, and (g) Θ0=13π20, respectively, with insets depicting zoomed-in views at the four corners of the samples. Calculated far-field images generated by three samples under illuminations of normally incident light with polarizations (d) Θ0=π4, (f) Θ0=π2, and (h) Θ0=13π20, respectively. Segments and circles indicate the local polarization states.

Fig. 4. Experimental set-up and characterizations on the first series of vectorial meta-holograms. (a) Experimental set-up for characterizing vectorial meta-holograms, with P, QWP, L, and O denoting polarizer, quarter-wave plate, lens, and optical lens, respectively. The inset illustrates an SEM picture and zoomed-in views of the first meta-hologram sample. (b) The first target holographic image and (c) experimentally observed pattern as the first meta-hologram sample is illuminated by LCP light at 1064 nm. Panels (d)–(g) depict the polarization filtered patterns with a rotatable polarizer placed at different angles in front of the CCD, as the first meta-hologram sample is illuminated by LCP light at 1064 nm. (h) The second target holographic image and (i) experimentally observed pattern as the second meta-hologram sample is illuminated by LCP light at 1064 nm. Panels (j)–(m) depict the polarization filtered patterns with a rotatable polarizer placed at different angles in front of the CCD, as the second meta-hologram sample is illuminated by LCP light at 1064 nm. Here, segments and circles denote local polarization states of the target holographic images.

Fig. 5. Characterizations on the second series of vectorial meta-holograms. Target holographic images to be reconstructed: (a) a vectorial clock, (g) a vectorial flower, and (m) a vectorial flying bird. Here, segments and circles denote local polarization states of the images. Panels (b), (h), and (n) depict the experimentally observed patterns as three fabricated meta-hologram samples are illuminated by LCP light at 1064 nm, respectively. Panels (c)–(f), (i)–(l), and (o)–(r) depict the polarization filtered patterns with a rotatable polarizer placed at different angles in front of the CCD, as three meta-hologram samples are illuminated by LCP light at 1064 nm, respectively.