Ultrafast modulation in a THz graphene-based flat absorber through negative photoconductivity

Quantitative exploration of the absorber behavior of metal-insulator-metal metamaterials within terahertz via an asymmetric peak model

Terahertz (THz) metamaterials have been developed for THz sensing, detection, imaging, and many other functions due to their unusual absorbers. However, the unusual absorption spectra change with different incident angles. Thus, we designed and fabricated a focal plane array with metal-insulator-metal (MIM) structure metamaterial absorbers for further research. The absorption spectrum with incident angles from 20 to 60 was measured using THz time-domain spectroscopy (THz-TDS), and the experimental results reveal that the absorption spectrum changes with incident angle variations. A basic analy…

Graphene-based Perfect Absorbers: Systematic Design and High Tunability

Experimental realization of efficient graphene-based absorbers is a challenging task due to the low carrier mobility in processed graphene. In this paper, we circumvent this problem by placing uniform graphene sheets on metallic metasurfaces designed for improving the absorption properties of low-mobility graphene. Complete absorption can be achieved for different frequencies with the proper metasurface design. In the THz band, we observe strong tunability of the absorption frequencies and magnitudes when modulating graphene Fermi level.

基于二氧化钒的超宽带太赫兹超材料吸收体的设计与分析

Design and Analysis of a Vanadium Dioxide-Based Ultra-Broadband Terahertz Metamaterial Absorber

本文设计并分析了一种基于VO2的超宽带太赫兹超材料吸收体，利用VO2相变实现动态调控，平均吸收率达98.15%，带宽5.38 THz，具有偏振不敏感和结构简单的优势。

Tunable and broadband coherent perfect absorbers with nonlinear and amplification performance based on asymmetric bifacial graphene metasurfaces

We present an asymmetric bifacial graphene metasurface to realize tunable and broadband coherent perfect absorption (CPA) at terahertz (THz) frequencies. The proposed design is composed of two dissimilar graphene square patch metasurfaces stacked over an ultrathin dielectric substrate. Nonlinear CPA performance without resorting to optical nonlinearities and amplification are demonstrated based on wave interference phenomena taking place along and inside this subwavelength structure. Broadband asymmetric reflection from opposite directions is obtained in the case of single wave illumination. T…

Efficient Absorption of Terahertz Radiation in Graphene Polymer Composites

We demonstrate that polymer composites with a low loading of graphene, below 1.2 wt. %, are efficient as electromagnetic absorbers in the THz frequency range. The epoxy-based graphene composites were tested at frequencies from 0.25 THz to 4 THz, revealing total shielding effectiveness of 85 dB (1 mm thickness) with graphene loading of 1.2 wt. % at the frequency f=1.6 THz. The THz radiation is mostly blocked by absorption rather than reflection. The efficiency of the THz radiation shielding by the lightweight, electrically insulating composites, increases with increasing frequency. Our results …

Terahertz frequency combs exploiting an on-chip solution processed graphene-quantum cascade laser coupled-cavity architecture

The ability to engineer quantum-cascade-lasers (QCLs) with ultrabroad gain spectra and with a full compensation of the group velocity dispersion, at Terahertz (THz) frequencies, is a fundamental need for devising monolithic and miniaturized optical frequency-comb-synthesizers (FCS) in the far-infrared. In a THz QCL four-wave mixing, driven by the intrinsic third-order susceptibility of the intersubband gain medium, self-lock the optical modes in phase, allowing stable comb operation, albeit over a restricted dynamic range (~ 20% of the laser operational range). Here, we engineer miniaturized T…