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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.

We propose a design of tunable double split-ring metamaterial (DSRM) in the terahertz (THz) frequency range. It is composed of a H-shaped resonator sandwiched by two face-to-face split-ring resonators (SRRs) on silicon on insulator (SOI) substrate. The electromagnetic responses of DSRM can be manipulated between single-resonance and dual-resonance by changing the incident polarization light, which shows polarization sensitive characteristic. DSRM exhibits a tunable function in the frequency range of 0.16 THz to 0.21 THz through enlarging the gap within two SRRs at TE mode. DSRM also shows stable characteristic by changing the distance between two face-to-face SRRs at TE and TM modes. Furthermore, to enhance the flexibility and applicability of DSRM, it is exposed on the surrounding environments with different refraction indexes. The correction coefficients are 0.997 for DSRM at TE and TM modes. These results show that DSRM exhibit the linear red-shifting of resonances by increasing the environmental refraction index. This work paves a way to the possibility of metamaterial devices with great tunability and polarization-dependence characteristics in the sensing applications.

We propose a novel infrared (IR) meta-absorber by using chalcogenide glass (ChG) material. The merits of ChG are zero extinction coefficient, excellent IR transparency, high third-order nonlinearity, adjustable refraction index, dispersion, and energy bandgap in IR wavelength range. Therefore, it is very suitable for the meta-absorber design. This ChG -based meta-absorber is composed of ring-disk nanostructures. The resonant wavelength and intensity of reflection spectra could be tuned by changing the outer ring of ring-disk nanostructures in horizontal and vertical displacements. The maximum quality factor (Q-factor) is 625. These unique characteristics of IR meta-absorber with ring-disk nanostructures can be used as a tunable IR filter and multi-resonance switch. Furthermore, the proposed device exhibits superior electromagnetic behaviors to be used as a high-efficiency environmental sensor.

We present and demonstrate a MEMS-based tunable terahertz metamaterial (TTM) composed of inner triadius and outer electric split-ring resonator (eSRR) structures. With the aim to explore the electromagnetic responses of TTM device, different geometrical parameters are compared and discussed to optimize the suitable TTM design, including the length, radius, and height of TTM device. The height of triadius structure could be changed by using MEMS technique to perform active tunability. TTM shows the polarization-dependent and electromagnetic induced transparency (EIT) characteristics owing to the eSRR configuration. The electromagnetic responses of TTM exhibit tunable characteristics in resonance, polarization-dependent, and electromagnetically induced transparency (EIT). By properly tailoring the length and height of the inner triadius structure and the radius of the outer eSRR structure, the corresponding resonance tuning range reaches 0.32 THz. In addition to the above optical characteristics of TTM, we further investigate its potential application in a refraction index sensor. TTM is exposed on the surrounding ambient with different refraction indexes. The corresponding key sensing performances, such as figure of merit (FOM), sensitivity (S), and quality factor (Q-factor) values, are calculated and discussed, respectively. The calculated sensitivity of TTM is 0.379 THz/RIU, while the average values of Q-factor and FOM are 66.01 and 63.83, respectively. These characteristics indicate that the presented MEMS-based TTM device could be widely used in tunable filters, perfect absorbers, high-efficient environmental sensors, and optical switches applications for THz-wave optoelectronics.