In this work, atomic layer deposition is applied to coat carbon nanocoils with magnetic Fe(3)O(4) or Ni. The coatings have a uniform and highly controlled thickness. The coated nanocoils with coaxial multilayer nanostructures exhibit remarkably improved microwave absorption properties compared to the pristine carbon nanocoils. The enhanced absorption ability arises from the efficient complementarity between complex permittivity and permeability, chiral morphology, and multilayer structure of the products. This method can be extended to exploit other composite materials benefiting from its convenient control of the impedance matching and combination of dielectric-magnetic multiple loss mechanisms for microwave absorption applications.

Metasurfaces offered great opportunities to control electromagnetic (EM) waves, but currently available meta-devices typically work either in pure reflection or pure transmission mode, leaving half of EM space completely unexplored. Here, we propose a new type of metasurface, composed by specifically designed meta-atoms with polarization-dependent transmission and reflection properties, to efficiently manipulate EM waves in the full space. As a proof of concept, three microwave meta-devices are designed, fabricated and experimentally characterized. The first two can bend or focus EM waves at different sides (i.e., transmission/reflection sides) of the metasurfaces depending on the incident polarization, while the third one changes from a wave bender for reflected wave to a focusing lens for transmitted wave as the excitation polarization is rotated, with all these functionalities exhibiting very high efficiencies (in the range of 85%-91%) and total thickness ~/8  . Our findings significantly expand the capabilities of metasurfaces in controlling EM waves, and can stimulate high-performance multi-functional meta-devices facing more challenging and diversified application demands.

Achieving multiple diversified functionalities in a single flat device is crucial for electromagnetic (EM) integration, but available efforts suffer the issues of device thickness, low efficiency, and restricted functionalities. Here, a general strategy to design high‐efficiency bifunctional devices based on metasurfaces composed by anisotropic meta‐atoms with polarization‐dependent phase responses is described. Based on the derived general criterions, two bifunctional metadevices, working in reflection and transmission modes, respectively, that can realize two distinct functionalities with very high efficiencies (≈90% in reflection geometry and ≈72% in transmission one) are designed and fabricated. Microwave experiments, including both far‐field and near‐field characterizations, are performed to demonstrate the predicted effects, which are in excellent agreement with numerical simulations. The findings in this study can motivate the realizations of high‐performance bifunctional metadevices in other frequency domains and with different functionalities, which are of crucial importance in EM integration.

Diffusive scatterings of electromagnetic (EM) waves by a thin screen are important in many applications, but available approaches cannot ensure uniform angular distributions of low-intensity scatterings without time-consuming optimizations. Here, we propose a robust and deterministic approach to design metasurfaces to achieve polarization-independent diffusive scatterings of EM waves within an ultrabroad frequency band and for wide-range of incident angles. Our key idea is to use high-efficiency Pancharatnam−Berry meta-atoms to form subarrays exhibiting focusing reflection-phase profiles, that can guarantee nearly uniform diffusive scatterings for arbitrarily polarized EM waves. As an illustration, we design and fabricate two metasurfaces and experimentally characterize their wave-diffusion properties in C, X, and Ku bands. Theoretical, numerical and experimental results demonstrate that our approach can diffuse the incident energy much more uniformly than available approaches based on the uniform-phase subarrays, thanks to the intrinsic wave-diffusion capabilities of the focusing-phase subarrays. The −7 dB fractional bandwidth is measured as 88.3% and the diffusive scattering behavior can be preserved up to 60°off-normal incidence irrespective of incident polarizations. Our approach, simple and robust, can help realize stealth applications under bistatic detections.

Nanocrystalline diamond nanomembranes with thinning-reduced flexural rigidities can be shaped into various 3D mesostructures, such as tubes, jagged ribbons, nested tubes, helices, and nested rings. Microscale helical diamond architectures are formed by controlled debonding in agreement with finite-element simulation results. Rolled-up diamond tubular microcavities exhibit pronounced defect-related photoluminescence with whispering-gallery-mode resonance.

Controlling the phase distributions on metasurfaces leads to fascinating effects such as anomalous light refraction/reflection, flat-lens focusing, and optics-vortex generation. However, metasurfaces realized so far largely reply on passive resonant meta-atoms, whose intrinsic dispersions limit such passive meta-devices’ performances at frequencies other than the target one. Here, based on tunable meta-atoms with varactor diodes involved, we establish a scheme to resolve these issues for microwave metasurfaces, in which the dispersive response of each meta-atom is precisely controlled by an external voltage imparted on the diode. We experimentally demonstrate two effects utilizing our scheme. First, we show that a tunable gradient metasurface exhibits single-mode high-efficiency operation within a wide frequency band, while its passive counterpart only works at a single frequency but exhibits deteriorated performances at other frequencies. Second, we demonstrate that the functionality of our metasurface can be dynamically switched from a specular reflector to a surface-wave convertor. Our approach paves the road to achieve dispersion-corrected and switchable manipulations of electromagnetic waves.

Manipulating the polarization states of electromagnetic (EM) waves, a fundamental issue in optics, attracted intensive attention recently. However, most of the devices realized so far are either too bulky in size, and/or are passive with only specific functionalities. Here we combine theory and experiment to demonstrate that, a tunable metasurface incorporating diodes as active elements can dynamically control the reflection phase of EM waves, and thus exhibits unprecedented capabilities to manipulate the helicity of incident circular-polarized (CP) EM wave. By controlling the bias voltages imparted on the embedded diodes, we demonstrate that the device can work in two distinct states. Whereas in the “On” state, the metasurface functions as a helicity convertor and a helicity hybridizer within two separate frequency bands, it behaves as a helicity keeper within an ultra-wide frequency band in the “Off” state. Our findings pave the way to realize functionality-switchable devices related to phase control, such as frequency-tunable subwavelength cavities, anomalous reflectors and even holograms.

Achieving flexible and highly directive emissions toward pre‐designed directions has intrigued long‐held interest in both science and engineering community, but most available efforts suffer the issues of bulky size, limited functionalities, and low efficiency. Here, we propose a general strategy to efficiently and flexibly control the emission beams with dual functionalities realized independently by orthogonal excitations. To overcome the polarization cross‐talking, a novel planar multi‐mode anisotropic meta‐atom is designed by incorporating the screening effect of a surrounding wire loop. As the result, we can design the polarization‐dependent phase profile under certain polarization, without worrying about their influences on the other polarization. As an illustration, two proof‐of‐concept metasurfaces are actualized at microwave frequencies, of which one combines the functionalities of focused‐beam and large‐angle multibeam emissions while another hybrids the functionalities of beam‐steering and small‐angle multibeam emissions. Theoretical, full‐wave simulation, and experimental results are in excellent agreement with each other, which collectively demonstrate the desired performances of our bifunctional devices. Our proposed strategy paves the way to realize high‐performance multifunctional optical devices with high integration and complex wavefront manipulations.