Abstract
Dynamically tunable band stop filter based on metal-graphene metamaterials is proposed and numerically investigated at mid-infrared frequencies. The proposed filter is constructed by unit cells with simple gold strips on the stack of monolayer graphene and the substrate of BaF2. A stable modulation depth up to −23.26 dB can be achieved. Due to the cooperative effect of the “bright-bright” elements, the amount of the gold strips in each unit cell determines the number of the stop-bands, providing a simple and flexible approach to develop multispectral devices. Further investigations illustrate that the location of the stop bands not only can be adjusted by varying the length of gold strips, but also can be dynamically controlled by tuning the Fermi energy level of graphene, and deep modulation is acquired through designing the carrier mobility. With the sensitivity as high as 2393 nm/RIU of the resonances to the varieties of surrounding medium, the structure is also enabled to be an index based sensor. The results will benefit the on plane or integrated micro-structure research with simple structure and flexible tunability, and can be applied in multi-band stop filters, sensors and other graphene-based multispectral devices.
Highlights
Electromagnetic (EM) metamaterials, a kind of artificially structured EM materials, are usually composed of periodically arranged subwavelength microstructures or ‘meta-molecules’, and have attracted great attention for their unique EM properties that the natural materials cannot realize
Traditional PIT based multispectral devices are usually designed by two approaches: the bright to bright mode coupling[12,13,14] and the bright to dark mode coupling[5,15,16], but usually come with an unsatisfactory modulation depth
With two gold strips acting as typical bright mode resonators, a dual-band stop filter with an ideal modulation depth as high as −23.26 dB is achieved
Summary
Electromagnetic (EM) metamaterials, a kind of artificially structured EM materials, are usually composed of periodically arranged subwavelength microstructures or ‘meta-molecules’, and have attracted great attention for their unique EM properties that the natural materials cannot realize. The combination of graphene and metamaterials can provide an effective approach to improve the dynamically tunable resonant properties of the multispectral devices[28,29,30,31]. With two gold strips acting as typical bright mode resonators, a dual-band stop filter with an ideal modulation depth as high as −23.26 dB is achieved. The dynamically tunable properties of the proposed filters are realized by adjusting the graphene Fermi energy, and the modulation depth can be designed through varying the carrier mobility. The proposed structure can be used as an index based sensor for its ultra-high sensitivity to the surrounding medium All these results demonstrated that the presented metal-graphene based metamaterials provide promising applications in multi-band stop filters, sensors and other graphene-based multispectral devices
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