Polarization optics plays a pivotal role in diffractive, refractive, and emerging flat optics, and has been widely employed in contemporary optical industries and daily life. Advanced polarization manipulation leads to robust control of the polarization direction of light. Nevertheless, polarization control has been studied largely independent of the phase or intensity of light. Here, we propose and experimentally validate a Malus-metasurface-assisted paradigm to enable simultaneous and independent control of the intensity and phase properties of light simply by polarization modulation. The orientation degeneracy of the classical Malus's law implies a new degree of freedom and enables us to establish a one-to-many mapping strategy for designing anisotropic plasmonic nanostructures to engineer the Pancharatnam-Berry phase profile, while keeping the continuous intensity modulation unchanged. The proposed Malus metadevice can thus generate a near-field greyscale pattern, and project an independent far-field holographic image using an ultrathin and single-sized metasurface. This concept opens up distinct dimensions for conventional polarization optics, which allows one to merge the functionality of phase manipulation into an amplitudemanipulation-assisted optical component to form a multifunctional nano-optical device without increasing the complexity of the nanostructures. It can empower advanced applications in information multiplexing and encryption, anti-counterfeiting, dual-channel display for virtual/augmented reality, and many other related fields.

Metasurfaces have recently been used for multichannel image displays with pixel-size lower than a wavelength, which indicates the potential application in ultracompact anticounterfeiting with high-density and hidden information. However, current multichannel metasurfaces applied in anticounterfeiting are based on the sophisticated nanostructure design or at the cost of giving up some controls on the optical transmission matrix to encode multiple information channels. That is, the overall degrees of freedom offered by these metasurfaces are a "zero-sum game". Here, inspired by the orientation degeneracy indicated in Malus law, we propose a multiplexed anticounterfeiting metasurface consisting of single-sized nanostructures, which provide a new degree of freedom to increase the information capacity of anticounterfeiting without burdening the nanostructure design and fabrication. Specifically, the proposed metasurfaces can record a continuous grayscale image (channel 1) multiplexed with a totally/partially independent, interrelated, or watermarked anticounterfeiting pattern (channel 2). The two channels can be readily switched by polarization control. All experimental metasurface-images (meta-images) with high fidelity agree well with our design. With advantages such as ultracompactness, high-density information, multichannel displays, and strong concealment, the anticounterfeiting metasurfaces can empower advanced research and applications of metasurfaces in high-end optical anticounterfeiting and many other related fields.

Metasurfaces capable of controlling more than two types of optical properties have drawn a broad interest recently, as they can bring great flexibility and possibilities to the design of highly-integrated multifunctional devices such as simultaneous nanoprint and holograms. However, current multifunctional metasurfaces can perform only two types of optical manipulations separately. Furthermore, their supercell or multilayer design strategies would complicate both the nanostructure design and manufacturing, and are difficult to implement the miniaturization, low-cost, and multifunctionality of light integration. Herein, merely with a single-cell design approach, a tri-functional metasurface enabled with triple manipulations of light is proposed. By merging the spectrum, polarization and phase manipulations into a single metasurface, a "three-in-one" meta-device simultaneously acting as a structural-color nanoprint, a polarization-controlled grayscale meta-image displayer and a phase-modulated meta-hologram can be constructed. Specifically, the structural-color image appears right at the metasurface plane under a natural light source while the grayscale meta-image and holographic image are reconstructed by taking different optical setups as decoding keys, which can not only significantly increase the light integration but also improve the reliability of both images. The proposed metasurface represents a new paradigm in designing multifunctional meta-devices, and has promising prospects in image displays, optical storage, optical anti-counterfeiting, etc.

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