Zero-order-free meta-holograms in a broadband visible range

The unwanted zero-order light accompanied by the birth of diffractive optical elements and caused mainly by fabrication errors and wavelength variations is a key factor that deteriorates the performance of diffraction-related optical devices such as holograms, gratings, beam shapers, beam splitters, optical diffusers, and diffractive microlenses. Here, inspired by the unique characteristic of nano-polarizer-based metasurfaces for both positive and negative amplitude modulation of incident light, we propose a general design paradigm to eliminate zero-order diffraction without burdening the metasurface design and fabrication. The experimentally demonstrated metahologram, which projects a holographic image with a wide angle of 70 degrees x 70 degrees in the far field, presents a very low zero-order intensity (only 0.7% of the total energy of the reconstructed image). More importantly, the zero-orderfree meta-hologram has a large tolerance limit for wavelength variations (under a broadband illumination from 520 to 660 nm), which brings important technical advances. The strategy proposed could significantly relieve the fabrication difficulty of metasurfaces and be viable for various diffractive-optics-related applications including holography, laser beam shaping, optical data storage, vortex beam generation, and so on. (C) 2020 Chinese Laser Press