Fig. 1. Schematic of the structural design of the meta-hologram. a, Phase control of two adjacent unit cells with distance . The cell is composed of a T-shaped nano-cavity in a gold film on a glass substrate. denotes the period length of a single cell. The two cells induce an optical path difference at the output angle . Each nano-cavity at different locations in period length produces different phases (between and ). b, Profile of the T-shaped nano-cavity. Gold film thickness is , and the upper groove width is . The width and the height 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 -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 and the groove height . The other parameters are , , and . The two points at (, ) and (, ) 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 ( for all groups, , 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, and , 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 , respectively. g–i, Reconstructed images at 633, 532, and 473 nm wavelength in the plane , respectively.
Fig. 4. a, Original 3D object comprises three letters (“N”, “R”, “C”) located at three planes , , , respectively. b–d, Reconstructed images at 633 nm wavelength in the three planes (, , ), respectively, based on the meta-hologram with complex amplitude modulation. e–g, Reconstructed images at 633 nm wavelength in the three planes (, , ), respectively, based on the phase-only meta-hologram.