Plasmonic metamaterial-based filtering structures with dynamic tunability.

In this Letter, we report the design, analysis, and characterization of first- and second-order plasmonic metamaterial-based multi-mode filtering structures. Further, electronic adaptivity in filter transfer functions is introduced and characterized. First, the basic operating principle of the engineered multi-mode resonator-based bandpass filter is presented. Then the concept is extended by introducing electronic (dynamic) tuning of the bandwidth using semiconductor varactor diodes. Afterwards, to enhance the selectivity and out-of-band filtering response, second-order multi-mode designs are realized. For experimental verification, the hardware prototype is fabricated and characterized using the Keysight analyzer N9918A. The design filtering structures will pave an important role in tunable plasmonic circuits and systems.