Fig. 1. Schematic of the structural design of the meta-hologram. a, Phase control of two adjacent unit cells with distance D. The cell is composed of a T-shaped nano-cavity in a gold film on a glass substrate. P denotes the period length of a single cell. The two cells induce an optical path difference ΔL at the output angle θ=arcsin(λ/P). Each nano-cavity at different locations in period length P produces different phases (between −π and π). b, Profile of the T-shaped nano-cavity. Gold film thickness is H=200nm, and the upper groove width is w1=50nm. The width w2 and the height h2 of the lower cavity are changed to control the transmittance amplitude. c, Typical 3D object reconstructed from the meta-hologram. When the meta-hologram is illuminated by a p-polarized light, the output beam generates the desired 3D object in free space.

Fig. 2. a, Amplitude transmittance through the T-shaped nano-cavity at 633 nm wavelength as a function of the groove width w2 and the groove height h2. The other parameters are P=1μm, H=200nm, and w1=50nm. The two points at (w2=200nm, h2=180nm) and (w2=200nm, h2=50nm) indicate the two cases of suppressed and enhanced transmittance, whose near-field electric-field distributions are shown in b and d, respectively. c, Normalized transmittance (left) and polarization extinction ratio (right) as functions of 10 groups of cavity structure parameters (h2=50nm for all groups, w2=0, 35, 50, 63, 72, 90, 105, 125, 150, 200 nm, respectively).

Fig. 3. a, Original 3D object comprises two Chinese oracle characters (“sheep” and “rabbit”) located at two planes, z1=100μm and z2=120μm, respectively. b, The 10-step quantized amplitude distribution in the hologram recording plane. c, The corresponding continuous phase distribution. d–f, Reconstructed images at 633, 532, and 473 nm wavelength in the plane z2=120μm, respectively. g–i, Reconstructed images at 633, 532, and 473 nm wavelength in the plane z1=100μm, respectively.

Fig. 4. a, Original 3D object comprises three letters (“N”, “R”, “C”) located at three planes z3=100μm, z2=80μm, z1=60μm, respectively. b–d, Reconstructed images at 633 nm wavelength in the three planes (z3, z2, z1), respectively, based on the meta-hologram with complex amplitude modulation. e–g, Reconstructed images at 633 nm wavelength in the three planes (z3, z2, z1), respectively, based on the phase-only meta-hologram.