Search for: All records

Engineered noise can increase the channel capacity for polarization multiplexing with a metasurface hologram. 

Abstract On the basis of the Jones matrix, independent control over the amplitude and phase of light has been demonstrated by combining several meta‐atoms into the supercell of a metasurface. However, due to the intrinsic limitation of a planar achiral structure, the maximum number of independent, complex elements in one Jones matrix is three, giving rise to up to three‐channel amplitude and phase control. In this work, more Jones matrices corresponding to different angles of incidence are proposed to add, so that the degrees of freedom in the amplitude and phase control can be further increased. The supercell of the designed metasurfaces consists of three dielectric nanoblocks with predefined rotation angles and displacements in the 2D space, which can be inversely determined with the help of the genetic algorithm. Empowered by the ability to realize four‐ or even eight‐channel amplitude and phase control, the generation of multiple structured light, including two independent perfect Poincaré beams, two double‐ring perfect Poincaré beams, two perfect Poincaré beam arrays, and four vector vortex beam arrays, is numerically demonstrated. Such novel designs are expected to benefit the development of modern optical applications, including but not limited to optical communications, quantum information, and signal encryption. 

This review focuses on the control over the degrees of freedom (DOF) in metasurfaces, which include the input DOF (the polarization, wavelength and incident angle of the input light and some dynamic controls), parameter DOF (the complex geometric design of metasurfaces) and output DOF (the phase, polarization and amplitude of the output light). This framework could clearly show us the development process of metasurfaces, from single-functional to multi-functional ones. Advantages of the multi-functional metasurfaces are discussed in the context of various applications, including 3D holography, broadband achromatic metalenses and multi-dimensional encoded information. By combining all the input and output DOF together, we can realize ideal optical meta-devices with deep subwavelength thickness and striking functions beyond the reach of traditional optical components. Moreover, new research directions may emerge when merging different DOF in metasurfaces with other important concepts, such as parity-time symmetry and topology, so that we can have the complete control of light waves in a prescribed manner.