Complex-amplitude metasurface-based orbital angular momentum holography in momentum space

Abstract

Digital optical holograms can achieve nanometer-scale resolution thanks to recent advances in metasurface technologies. This has raised hopes for applications in data encryption, data storage, information processing and displays. However, the hologram bandwidth has remained too low for any practical use. To overcome this limitation, information can be stored in the orbital angular momentum (OAM) of light, as this degree of freedom has an unbounded set of orthogonal helical modes that could function as information channels. Thus far, OAM holography has been achieved using phase-only metasurfaces, which however are marred by channels crosstalk. As a result, multiplex information from only 4 channels has been demonstrated. Here we demonstrate an OAM holography technology that is capable of multiplexing up to 200 independent OAM channels. This is achieved by designing a complex-amplitude metasurface in momentum-space capable of complete and independent amplitude and phase manipulation. Information is then extracted by Fourier transform using different OAM modes of light, allowing lensless reconstruction and holographic videos being displayed. Our metasurface can be 3D printed in a polymer matrix on SiO2 for large-area fabrication.