In this paper, we present an easy-to-implement metamaterial absorber based on bulk Dirac semimetal (BDS). The proposed device not only obtains an ultrahigh quality factor (Q-factor) of 4133 and dynamic adjustability at high absorption, but also exhibits an excellent sensing performance with a figure of merit (FOM) of 4125. These outstanding properties are explained by the surface lattice resonance, which allows us to improve the quality factor significantly and control resonance wavelength precisely by tuning the unit cell periods, Fermi energy of the BDS, and structural parameters. Our findings can provide high-performance applications in terahertz filtering, detection, and biochemical sensing.

We propose a design of bilayer metasurfaces, imposing arbitrary and independent phase profiles on arbitrarily polarized beams at λ1=505nm and circularly polarized beams at λ2=633nm. The method cascades two layers that separately function as convertible waveplates and full-wave plates for modulation of polarization and phase. We investigate performances of the asymmetric deflector and multi-foci metalenses. Specifically, polarization-independent deflector or single-focus metalens can be achieved at λ1, while polarization-dependent deflector or dual-foci metalens are designed at λ2. These results demonstrate a simple yet effective approach interconnecting phase distributions and flexible polarization responses, which holds great promise in information multiplexing and security.

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We propose a composite metasurface composed of InSb strips and SiO 2 substrate, which can achieve multi-band coherent perfect absorption in the terahertz frequency range. It is demonstrated that InSb strips of different sizes support independent plasmon resonances at different frequencies, which is a linear superposition of each subunit. The absorption at each resonance frequency can be independently and continuously modulated with the modulation depth is up to 1.332 × 10 4 via controlling the relative phase or relative intensity of two beams. Meanwhile, the absorber has the sensitivity of the refractive index to the surrounding environment, thereby facilitating the design of sensing devices. Moreover, it has excellent thermal tunability: we flexibly modulate absorption via controlling the temperature without restructuring. Our design contributes a feasible way of manipulating the interaction between light and matter, which can be applied to the field of micro-nano photonic devices in the terahertz band.

Terahertz sensing is one of the most promising methods for label free and noninvasive detection of refractive index changes. However, the figure of merit (FOM) of terahertz sensor has been low due to the low radiation and absorption loss of terahertz wave. In this paper, a metamaterial sensor based on gold and silicon dioxide is proposed. The structure not only realizes narrow-band absorption with five absorption peaks, but also improves FOM to 1792. These excellent performances are based on the classical magnetic resonance and Mie resonance, which provide a platform for the design of multi-band photodetectors and high sensitivity sensors.