The colour gamut, a two-dimensional (2D) colour space primarily comprising hue and saturation (HS), lays the most important foundation for the colour display and printing industries. Recently, the metasurface has been considered a promising paradigm for nanoprinting and holographic imaging, demonstrating a subwavelength image resolution, a flat profile, high durability, and multi-functionalities. Much effort has been devoted to broaden the 2D HS plane, also known as the CIE map. However, the brightness (B), as the carrier of chiaroscuro information, has long been neglected in metasurface-based nanoprinting or holograms due to the challenge in realising arbitrary and simultaneous control of full-colour HSB tuning in a passive device. Here, we report a dielectric metasurface made of crystal silicon nanoblocks, which achieves not only tailorable coverage of the primary colours red, green and blue (RGB) but also intensity control of the individual colours. The colour gamut is hence extruded from the 2D CIE to a complete 3D HSB space. Moreover, thanks to the independent control of the RGB intensity and phase, we further show that a single-layer silicon metasurface could simultaneously exhibit arbitrary HSB colour nanoprinting and a full-colour hologram image. Our findings open up possibilities for high-resolution and high-fidelity optical security devices as well as advanced cryptographic approaches.

Plasmonic colour printing has drawn wide attention as a promising candidate for the next-generation colour-printing technology. However, an efficient approach to realize full colour and scalable fabrication is still lacking, which prevents plasmonic colour printing from practical applications. Here we present a scalable and full-colour plasmonic printing approach by combining conjugate twin-phase modulation with a plasmonic broadband absorber. More importantly, our approach also demonstrates controllable chromotropic capability, that is, the ability of reversible colour transformations. This chromotropic capability affords enormous potentials in building functionalized prints for anticounterfeiting, special label, and high-density data encryption storage. With such excellent performances in functional colour applications, this colour-printing approach could pave the way for plasmonic colour printing in real-world commercial utilization.

The integration of single-photon sources and metasurfaces provides powerful conceptual structures for quantum optics applications.

Due to its unbounded and orthogonal modes, the orbital angular momentum (OAM) is regarded as a key optical degree of freedom (DoF) for future information processing with ultra-high capacity and speed. Although the manipulation of OAM based on metasurfaces has brought about great achievements in various fields, such manipulation currently remains at single-DoF level, which means the multiplexed manipulation of OAM with other optical DoFs is still lacking, greatly hampering the application of OAM beams and advancement of metasurfaces. In order to overcome this challenge, we propose the idea of multiplexed coherent pixel (MCP) for metasurfaces. This approach enables the manipulation of arbitrary complex-amplitude under incident lights of both plane and OAM waves, on the basis of which we have realized the multiplexed DoF control of OAM and wavelength. As a result, the MCP method expands the types of incident lights which can be simultaneously responded by metasurfaces, enriches the information processing capability of metasurfaces, and creates applications of information encryption and OAM demultiplexer. Our findings not only provide means for the design of high-security and high-capacity metasurfaces, but also raise the control and application level of OAM, offering great potential for multifunctional nanophotonic devices in the future.