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A design of electric split-ring metamaterial (eSRM) with tunable terahertz (THz) free spectra range (FSR) characteristic is presented. The proposed eSRM is composed of double semicircle-shaped ring resonators with two connected metallic bars. By changing the radius of the semicircle-shaped ring resonators, the tuning ranges of FSR are 0.187 THz and 0.024 THz in transverse electric (TE) and transverse magnetic (TM) modes, respectively, which indicates eSRM could operate stably in TE and TM modes. Furthermore, eSRM exhibits switching and polarization-dependent characteristics by exploiting comb driver to control the distances between ring resonators along ${x}$ -and ${y}$ -axis directions. The electromagnetic responses could be tuned and switched between dual- and quad-resonance in both TE and TM modes. eSRM shows polarization angle-sensitive characteristic and the corresponding FSR could be tuned from 919 GHz to 336 GHz by changing the polarization angle of incident THz wave. In view of the above optical characteristics of eSRM, it is used for the sensing application exposed on different surrounding refraction index. The sensitivity, quality factor (Q-factor), and figure of merit (FOM) are calculated. The sensitivity is 0.457 THz/RIU and the average Q-factor and FOM are 40.65 and 35.47, respectively. These results indicate the proposed eSRM could be used in widespread applications, such as dual-/quad-resonance switches, polarization switches, and high-efficient environmental sensors. [2021-0006]

We propose and demonstrate a metamaterial design by integrating a microelectromechanical system (MEMS) electrothermal actuator (ETA) platform and a cross-shaped metamaterial (CSM) to perform opto-logic function characteristics. Reconfigurable and stretchable mechanisms of CSM are achieved by driving different DC bias voltages on ETA to improve the limitations induced by the conventional use of the flexible substrate. The optical responses of CSM are tunable by the electrical signals inputs. By driving a DC bias voltage of 0.20 V, a tuning range of CSM is 0.54 THz is obtained and it and provides perfect zero-transmission characteristics. In addition, the "XNOR" logic gate function of CSM is realized at 1.20 THz, which plays a key role in the all opto-logic network communication system. The proposed MEMS-based CSM exhibits potential applications in logical operation, signal modulation, optical switching, THz imaging, and so on.

We propose two tunable metareflectors (MRs) composed of a suspending nanodisk and an annular hole on silicon (Si) substrate with aluminum (Al) mirrors atop. They are denoted as MR-1 and MR-2 for the former and latter, respectively. The proposed MRs exhibit high-efficient cyan-magenta-yellow (CMY) color filtering, and ultrabroad tuning range characteristics. The electromagnetic energy of the resonant wavelength is confined within the suspending nanostructure and bottom Al mirror and then performed a perfect absorption. By changing the height between suspending nanostructure and the bottom Al mirror, MRs exhibit active tuning and single-/dual-resonance switching characteristics spanning the entire visible spectra range. Furthermore, the resonant wavelengths of MRs are sensitive to the surrounding ambient media, which are red-shifted and modulated from single- to dual-resonance by changing the environmental refraction index. The corresponding sensitivities are 500 nm/RIU and 360 nm/RIU for MR-1, 289 nm/RIU and 270 nm/RIU for MR-2, respectively. These results provide an effective strategy for use in high-resolution displays, high-sensitive sensors, optical switches, optical communications, and flexible virtual reality (VR)/augmented reality (AR) applications.

The integration of micro-electro-mechanical system (MEMS) with metamaterial has provided a novel route to achieve programmability via its reconfigurable capabilities. Here, we propose and demonstrate a MEMS-based metadevice by using switchable winding-shaped cantilever metamaterial (WCM) for active logical modulation. WCM can be actuated by external driving voltage, and the logical modulation bit is performed by releasing MEMS cantilevers to represent “on” and “off” states. While the underneath substrate surface of a MEMS-based metadevice is rough after releasing the cantilevers, the metadevice is allowed to operate on the reconfigurable switching state and avoid the snapping down of the device when the system is overloaded. Such a reconfigurable and programmable MEMS-based metadevice exhibits multifunctional characteristics to simultaneously perform the logic operations of “OR” and “AND” gates. By exploiting the tuning mechanism of the MEMS-based metadevice, the arbitrary metamaterial configuration can be implanted into WCM. This opens a wide avenue to further enlarge the operating frequency range and applications in optoelectronic fields. These unique results provide various possibilities in multifunctional switching, active logical modulating, and optical computing applications.