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We present a single-layer H-shaped all-silicon array exhibiting tunable ultra-broadband terahertz wave absorption. Experiment and simulation reveal near unity absorption at ~1 THz, with a bandwidth of ~913 GHz for ≥90% absorbance. The absorption is optically tunable, exhibiting a resonance frequency blueshift by 420 GHz, while the peak absorbance remains over 99%. The dynamic response upon optical excitation depends upon the penetration depth of the pump beam in silicon, as demonstrated from simulation taking into account the depth dependence of the carrier concentration in the all-silicon metamaterial perfect absorber. The results unveil the tuning mechanisms in optically tunable all-silicon metamaterials and metasurfaces, guiding the development of functional all-dielectric functional terahertz devices, such as switches and modulators.

In this paper, we present a polarization insensitive air-spacer triple band absorber. With the fabricated absorber, the three near unity-absorption peaks can be fine controlled with different structure designs, which have a great advantage in variety applications. Also, with air instead of the traditional dielectric layer, the absorber will exhibit an extremely high quality factor (Q) compare with the one in dielectric layer. Moreover, with the air-spacer triple band absorber structure, the coupling between the metamaterials layer and the ground plane is very strong. As a result, the near-field interaction should be considered in the interference theory. With the coupling effect included, the correctional interference theory can well predict both the numerical and experiment results of the metamaterial perfect absorber. Our findings demonstrate that the capacitance increase and the inductance decrease are the causes of the difference between the interference theory and the simulation and experiment results especially for circles metamaterials structures with thin air-spacer in metamaterial perfect absorber.

In this paper, we present a three-dimensional (3D) terahertz metamaterial perfect absorber (MPA) with a high quality factor. The absorption response of the proposed structure is analyzed and optimized using coupled mode theory and numerical simulations. Subsequently, we fabricate the 3D MPA by employing the multi-layer electroplating process and characterize it using terahertz time domain spectroscopy. A quality factor of 20 is verified by the experimental results, which agrees well with the simulation. The high-Q MPA has potential applications in chemical and biological sensing.

We designed, fabricated, and characterized a metamaterial perfect absorber at terahertz (THz) frequency range utilizing air as the dielectric material. Due to the avoidance of the loss usually introduced by the dielectric material, there was a three times improvement of the quality factor. Also, with metamaterials fabricated on a free-standing silicon nitride membrane, high sensitivity can be achieved compared with traditional metamaterials on thick substrate. Moreover, the absence of the dielectric materials presents the special opportunity to use liquid or gas as the dielectric layer for permittivity characterization or sensing and detection purposes

This paper reports a mechanically tunable terahertz metamaterial based on microscale electrostatic actuators. The device consists of an array of suspended cantilevers, forming LC resonators with underlying capacitive pads. The applied voltage can pull the cantilever downwards to increase the capacitance value in the resonator, and thus, redshift the resonant frequency. In our preliminary experiments, the resonant frequency can be tuned from 1.105 THz to 1.06 THz under a 40 V voltage; at the same time, the transmission amplitude can be modulated by approximately 15 dB at the resonant frequencies. The results enables the implementation of tunable terahertz devices, including modulators, polarizers and waveplates, employing conventional micro-electromechanical structures.