A new concept of the coding phase gradient metasurface (CPGM) is proposed, which is constructed using the phase gradient metasurface as the coding elements. Different from the previous coding metasurface (CM), both the coding sequences and gradient phases in the coding elements are designed to manipulate the electromagnetic (EM) wave for the CPGMs, and thus the manipulation will be more flexible. As an example, wide-band, wide-angle CPGMs with zero and non-zero phase gradient based on Pancharatnam-Berry (PB) phase are achieved using the co-polarization reflection unit cells under circularly polarized (CP) wave incidence. Both theoretically calculated and numerically simulated scattering patterns of the designed CPGMs demonstrate the expected manipulations. Additionally, two kinds of random CPGMs with different phase gradients are designed for radar cross section (RCS) reduction, and the measured RCS reveals a good accordance with the simulation.

The power of controlling objects with mind has captivated a popular fascination to human beings. One possible path is to employ brain signal collecting technologies together with emerging programmable metasurfaces (PM), whose functions or operating modes can be switched or customized via on-site programming or pre-defined software. Nevertheless, most of existing PMs are wire-connected to users, manually-controlled and not real-time. Here, we propose the concept of remotely mind-controlled metasurface (RMCM) via brainwaves. Rather than DC voltage from power supply or AC voltages from signal generators, the metasurface is controlled by brainwaves collected in real time and transmitted wirelessly from the user. As an example, we demonstrated a RMCM whose scattering pattern can be altered dynamically according to the user’s brain waves via Bluetooth. The attention intensity information is extracted as the control signal and a mapping between attention intensity and scattering pattern of the metasurface is established. With such a framework, we experimentally demonstrated and verified a prototype of such metasurface system which can be remotely controlled by the user to modify its scattering pattern. This work paves a new way to intelligent metasurfaces and may find applications in health monitoring, 5G/6G communications, smart sensors, etc.

An approach to expanding a Gaussian beam in terms of the spheroidal wave functions in spheroidal coordinates is presented. The beam-shape coefficients of the Gaussian beam in spheroidal coordinates can be computed conveniently by use of the known expression for beam-shape coefficients, g(n), in spherical coordinates. The unknown expansion coefficients of scattered and internal electromagnetic fields are determined by a system of equations derived from the boundary conditions for continuity of the tangential components of the electric and magnetic vectors across the surface of the spheroid. A solution to the problem of scattering of a Gaussian beam by a homogeneous prolate (or oblate) spheroidal particle is obtained. The numerical values of the expansion coefficients and the scattered intensity distribution for incidence of an on-axis Gaussian beam are given.

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RNA is ideally suited for in vitro evolution experiments, because a single RNA molecule possesses both genotypic (replicable sequence) and phenotypic (selectable shape) properties. Using systematic evolution of ligands by exponential enrichment (SELEX), we found a single 58-nt aptamer sequence that assumes two structures with different functions, both of which are required to inhibit the GluR2 AMPA receptor channel. Yet, the two structures, once formed during transcription, appear to be incapable of interconverting through unfolding and refolding, presumably due to their extraordinary structural stability. Thus, our results suggest more broadly that natural RNA molecules can evolve to acquire alternative structures and associated functions. Such divergence of RNA phenotype may precede gene duplication at the genome level.

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Vortex beams with orbital angular momentum (OAM) can remarkably increase the channel capacity without signal process, thus attract more and more attention of researchers, and various novel methods of generating vortex beams blow out. In this work, a circular-polarized vortex beam reflector antenna was proposed via integrating vortex beam generated metasurface and beam focusing metasurface. The antenna consists of the metasurface reflector and a feed helical antenna. The phase distribution of the metasurface combines the OAM phase distribution and the beam focusing required phase distribution which is used to generate vortex beam from a point source. The measured results agree well with the simulated results, and both demonstrate that the reflector antenna can generate a vortex beam with OAM from 12 GHz to 18 GHz, and the realized gain is 22.4 dB at the center frequency 15 GHz.

A two-dimensional (2D) coding phase gradient metasurface (CPGM) is proposed for radar cross section (RCS) reduction in this work. The 2D phase gradient super cell is employed to serve as the coding element. The primary pattern of the coding element will be modulated by the designed 2D phase gradient. Thus, a more flexible method of scattering manipulation will be achieved by both the 2D phase gradient and coding sequences. The specific scattering patterns of the 2D CPGM under the modulation of phase gradient and coding sequence were analyzed. A controllable backward diffusion scattering coding phase gradient metasurface was realized based on Pancharatnam–Berry phase by modulating both the phase gradient and coding sequence. Both simulated and measured results demonstrate its excellent performance on RCS reduction.