Bidirectionally excited dual PIT device based on graphene patterns on a flexible substrate

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Abstract In this work, a facile double-layer graphene-flexible substrate metamaterial device is developed, enabling the realization of dual plasmon-induced transparency (PIT) response. The device comprises rectangular and circular graphene patterned elements, in which the circular graphene is encapsulated between two polyimide (PI) layers, while the rectangular graphene is anchored on a PI substrate with air as the upper cladding. The electromagnetic characteristics of graphene can be dynamically modulated via varying the Fermi level, thus achieving active tunability of the PIT resonant frequency and transmission window performance. Plasmon-induced transparency devices are multifunctional, serving as both sensors and optical switches. The modulation effects and underlying mechanism of geometric parameters, Fermi level and incident polarization on the transmission spectrum of the device are systematically explored. This device is capable of serving as a refractive index sensor, with a maximum sensitivity of 1.3 THz/RIU. It can also be utilized as an optical switch. At the frequency of 5.18 THz under Y-polarized incident light, tuning the Fermi level enables the device to attain a maximum modulation depth of 89% and an extinction ratio up to 9.59 dB. In contrast, by regulating the incident polarization direction, the device achieves a peak modulation depth of 77.5% and a maximum extinction ratio of 6.48 dB. This designed device exhibits outstanding performance, showing promising application prospects in terahertz refractive index sensing and polarization-regulated optical switches.

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