Malus-metasurface-assisted polarization multiplexing

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 amplitude-manipulation-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 made from an array of carefully orientated silver nano-brick polarizers on a silica glass substrate can manipulate the phase and amplitude of light. Fabricated and characterized by a team of researchers in China, Singapore and the UK, the so-called Malus metasurfaces are optimally designed to operate with red light and generate near-field greyscale patterns and far-field holographic images. Potential uses include image multiplexing and encryption, augmented-reality displays and other applications. The metasurfaces consist of nanoscale (160 nm long, 80 nm wide and 70 nm high) cuboids of silver which have a long axis and short axis. Simulations indicate that the nanobricks reflect 92.6% of incident 633 nm-light when its polarization is aligned along the long axis and transmit 95.3% when aligned to its short axis, thus acting as a nanoscale polarizer.