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Spoof LSP (Localized Surface Plasmon) is a great advance in metamaterials, expanding the LSP resonance from optical band into microwave band. It will yield amazing outcomes by integration with flexible electronics, wearable electronics and nanophotonics. Here, an ultrathin and flexible spoof LSP prepeared by layer-by-layer (LBL) assembly of gold nanoparticles was demonstrated. The LSPR effects in microwave band was assembly-induced and the electric resonance component disappeared, which is significantly different from that of the spoof LSPs by bulk metal. It was thought and proved by simulation to be relative with the special micro-structure of the gold nanoparticle assemblies. Furthermore, the spoof LSP by gold nanoparticles was flexible and showed a strong relationship between the resonance frequency and the curvature degree of the spoof LSP, meaning that the LSP resonance can be modulated by the deformation of the spoof LSP. We believed that these results could deepen understanding about the spoof LSPs and widen the application in multiple areas.

Metamaterials have attracted tremendous amount of interests owing to their tempting electromagnetic responses. Based on the metamaterials, many novel practical electromagnetic devices have been realized in the microwave, terahertz, and optical frequencies. Recently, a new type of metamaterial filter has attracted growing attention. Based on the method of hybrid multiple resonances, the metamaterial filter possesses a notable spectral-filtering capability with broad bandwidth and excellent band-edge transitions. In this letter, we report the design, fabrication, and measurement of a polarization insensitive wide-angle triple-band metamaterial bandpass filter (BPF) in the microwave frequency. The proposed BPF consists of two identical metal resonant units which have three concentric square slots separated by a dielectric layer. Experimental results show that the BPF has three distinctive transmission bands centered at frequencies 6.22 GHz, 9.46 GHz and 12.14 GHz with transmission rates of −0.40 dB, −0.71 dB and −1.40 dB, respectively, agreeing well with simulation results. By introducing the substrate integrated waveguide (SIW), it is shown that the filter is valid to a wide range of incident angles for both transverse electric (TE) and transverse magnetic (TM) polarizations. The triple-band metamaterial BPF is a promising candidate as new filters and radomes owing to its multiband transmissions, polarizations insensitive, and wide-angle responses.

In this letter, we report the design, fabrication and measurement of a polarization insensitive wide-angle triple-band metamaterial bandpass filter (BPF) in the microwave frequency. The proposed BPF consists of two identical metal resonant units which have three concentric square slots separated by a dielectric layer. Experimental results show that the BPF has three distinctive transmission bands centered at frequencies 6.22 GHz, 9.46 GHz and 12.14 GHz with transmission rates of −0.40 dB, −0.71 dB and −1.40 dB, respectively, agreeing well with simulation results. By introducing the substrate integrated waveguide, the filter is valid to a wide range of incident angles for both transverse electric and transverse magnetic polarizations. The triple-band metamaterial BPF can be used as multiband filters and radomes owing to its multiband transmissions, polarizations insensitive and wide-angle responses.