Graphene as a new two-dimensional material can be utilized to design tunable optical devices owing to its exceptional physical properties such as high mobility and tunable conductivity. In this paper, we present the design and analysis of a tunable broadband terahertz absorber based on periodic graphene ring arrays. Due to plasmon hybridization modes excited in the graphene ring, the proposed structure achieves a broad absorption bandwidth with more than 90% absorption in the frequency range of 0.88-2.10THz under normal incidence and its relative absorption bandwidth is about 81.88%. Meanwhile, it exhibits polarization-insensitive behavior and maintains high absorption over 80% when incident angle is up to 45º for both TE and TM polarizations. Additionally, the peak absorption rate of the absorber can be tuned from 21% to nearly 100% by increasing the graphene’s chemical potential from 0eV to 0.9eV. Such a design can have some potential applications in various terahertz devices, such as modulators, detectors, spatial filters.

The recognition of coal-rock interface is very crucial for the research in the intelligent production of coal mine. This study investigates the application of terahertz time-domain spectroscopy in the recognition of coal-rock interface, including the identification of coal-rock and coal-rock mixtures, as well as the accurate characterization of coal seam thickness. Terahertz detection was used to obtain the optical parameter information of the pressed pellets prepared by mixing two different kinds of coal and two kinds of rock. Based on the experiment results, the database was established for the identification of coal-rock interfaces in coal mining machines. The terahertz detection was performed on 10 different kinds of sheet anthracite with different thickness, and the terahertz spectra of coal seams with different thickness were simulated and calculated by using simulation software, which can accurately obtain the thickness of coal seams and provide effective mining thickness parameters for coal seam mining. Through the experiment and simulation, the terahertz time-domain spectroscopy technology has a promising application prospect in the identification of coal-rock interface.