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.

A dynamically tunable anisotropic narrowband absorber based on monolayer black phosphorous (BP) is proposed in the terahertz (THz) band. The proposed absorber consists of a monolayer BP and a silicon (Si) grating, which is placed on a silica (SiO2) isolation layer and a gold (Au) substrate. The benefit from the critical coupling mechanism with guided resonance is the efficiency of the absorption can reach 99.9% in the armchair (AC) direction and the natural anisotropy of BP makes it only 87.2% in the zigzag (ZZ) direction. Numerical and theoretical studies show that the absorption efficiency of the structure is operatively controlled by critical coupling conditions, including the geometric parameters of the Si grating, the electron doping of BP and the angle of incident light, etc. More importantly, in the absence of plasmon response, this structure greatly enhances the interaction between light and matter in monolayer BP. In particular, there are several advantages in this structure, such as extremely high-efficiency absorption, excellent tunability, outstanding intrinsic anisotropy and easy manufacturing, which will show unusual and promising potential applications in the design of BP-based tunable high-performance devices.

We report a numerical and theoretical study of the plasmon-induced transparency (PIT) effect in bulk Dirac semimetal (BDS) waveguide. This plasmon waveguide system is composed of a bus waveguide side coupled with two stub photoactive silicon resonators. The coupled mode theory (CMT) is introduced to analyze this system, and the theoretical results are perfectly consistent with the numerical calculation results. The numerical results show that the spectral characteristics of the structure depend on the coupling distance between the two stub photoactive silicon resonators. Intriguingly, the resonance characteristics of the transparent window can be actively controlled by adjusting the Fermi energy of the BDS or the intensity of the incident pump light. Finally, the group time delay of the PIT window can reach 3.7 ps, which is more suitable for applications with slow-light devices. Such a simple and multi-functional plasmon system is more conducive to the potential applications of composite high-performance devices.

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.