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1 of 9) 1600202 wileyonlinelibrary.com solid venues for further developments, [9,10] including 1D SPP waveguides [11][12][13] and networks. [14][15][16] Owing to the fact that metals behave as perfectly electric conductors (PECs) at the far infrared, terahertz, and microwave frequencies, SPPs cannot be achieved in their original way. Alternatively, plasmonic metamaterials have been proposed to construct designer SPPs [2,17] (also termed as spoof SPPs [18] ) in the lower frequencies.Metamaterials and photonic crystals are macroscopic composites with controllable EM properties when the geometry and dimension of their composing particles are tuned. [19] Based on this inherent property of metamaterials or photonic crystals, the physical characteristics of designer SPPs can be tailored by tuning the geometrical parameters. [20][21][22][23][24][25][26][27][28] Besides the feature of slow waves, [27] the designer SPP structures can also achieve tight field confinements and remarkable field enhancements [20][21][22][23][25][26][27][28] in microwave and terahertz frequencies due to their properties of exponential decay of fields in all directions perpendicular to the patterned interface (i.e., the spatial waveguide modes do not exist around the designer SPP structures). This is quite different from the conventional slow-wave structures in the microwave frequencies. [29][30][31][32] In recent years, active metamaterials and metasurfaces have been developed toward the dynamic functionalities such as switching and modulating EM waves. [33] To attain the dynamic functionalities, a series of approaches have been proposed (e.g., the microelectromechanical technology, [34] phase-change media, [35,36] superconductors, [37] carrier injection or depletion in semiconductor substrates, [38] etc.), and many tunable metamaterial devices have been created accordingly. [35][36][37][38] Most recently, the concepts of coding and programmable metasurfaces have been proposed to control the scattering/radiation performance of spatial EM waves using the "0" and "1" meta-elements, which are the unit cells with opposite reflection-phase responses. [39] However, such coding and programmable metasurfaces were limited to control the behaviors of spatial waves, for example, to engineer the EM scattering and radiation of objects. [39] To the best knowledge of the authors, programmable SPPs and/or designer SPPs have not been reported.Here, we explore the concepts of coding and programmable designer SPPs and propose a new kind of planar SPP waveguide Manipulating the dispersion behaviors of electromagnetic (EM) waves at subwavelength scale provides many exciting physical phenomena and functionalities such as the phase matching, gain enhancement, super resolution, and slow light. Among the dispersion manipulations, surface plasmon polaritons (SPPs) are typical EM modes to control the wave flows owing to their sensitivity to the designed decorations on the metal-dielectric interfaces. However, either on metal-dielectric interfaces or decoration surfaces,...

Perfect lenses, superlenses and time-reversal mirrors can support and spatially separate evanescent waves, which is the basis for detecting subwavelength information in the far field. However, the inherent limitations of these methods have prevented the development of systems to dynamically distinguish subdiffraction-limited signals. Utilizing the physical merits of spoof surface plasmon polaritons (SPPs), we demonstrate that subdiffraction-limited signals can be transmitted on planar integrated SPP channels with low loss, low channel interference, and high gain and can be radiated with a very low environmental sensitivity. Furthermore, we show how deep subdiffraction-limited signals that are spatially coupled can be distinguished after line-of-sight wireless transmission. For a visualized demonstration, we realize the high-quality wireless communication of two movies on subwavelength channels over the line of sight in real time using our plasmonic scheme, showing significant advantages over the conventional methods.

We propose a method to design a transmission-spectrum-controllable spoof surface plasmon polaritons (SPPs) based on the interaction between spoof SPP waveguide and frequency tunable metamaterial (MTM) particles. To achieve the tunable MTM particles, we introduce varactor-diodes into split-ring resonators (SRRs). Taking the advantage of sub-wavelength scale of SRRs, we design and fabricate a compact transmission-spectrum-controllable spoof SPPs. Both simulated and measured results demonstrate excellent dynamic control of transmission coefficients at microwave frequencies.

Digital coding and digital modulation are the foundation of modern information science. The combination of digital technology with metamaterials provides a powerful scheme for spatial and temporal controls of electromagnetic waves. Such a technique, however, has thus far been limited to the control of free-space light. Its application to plasmonics to shape subwavelength fields still remains elusive. Here, we report the design and experimental realization of a tunable conformal plasmonic metasurface, which is capable of digitally coding and modulating designer surface plasmons at the deep-subwavelength scale. Based on dynamical switching between two discrete dispersion states in a controlled manner, we achieve digital modulations of both amplitude and phase of surface waves with nearly 100% modulation depth on a single device. Our study not only introduces a new approach for active dispersion engineering, but also constitutes an important step towards the realization of subwavelength integrated plasmonic circuits.