Abstract-Sensitive characterizations of natural dolomite by terahertz time-domain spectroscopy

Sibo Hao, Haochong Huang,  Yuanyuan Ma,  Zili Zhang,  Zhiyuan Zheng,



https://www.sciencedirect.com/science/article/abs/pii/S0030401819307990

The pyrolysis and the porosity of natural dolomite are investigated by terahertz time-domain spectroscopy for primary quality control in industry. From terahertz spectra, the transformation of natural dolomite modified by calcination can be clearly differentiated. Based on such results, the thermal active dolomite is studied on adsorbing copper ions in water at first glance. Also, the terahertz maps highlight the subtle variations of the nominal porosity existing in dolomite. In particular, the refractive index and absorption coefficients evidence the variation of mineral properties within natural dolomite. Compared with traditional methods, terahertz time-domain spectroscopy is thus of great significances to gain a non-destructive and contact-free understanding of natural minerals, even in geological studies and environmental industries.

Abstract-Terahertz lens made out of natural stone

Daehoon Han, Kanghee Lee, Jongseok Lim, Sei Sun Hong, Young Kie Kim, and Jaewook Ahn  »View Author Affiliations

Terahertz (THz) time-domain spectroscopy probes the optical properties of naturally occurring solid aggregates of minerals, or stones, in the THz frequency range. Refractive index and extinction coefficient measurement reveals that most natural stones, including mudstone, sandstone, granite, tuff, gneiss, diorite, slate, marble, and dolomite, are fairly transparent for THz frequency waves. Dolomite in particular exhibits a nearly uniform refractive index of 2.7 over the broad frequency range from 0.1 to 1 THz. The high index of refraction allows flexibility in lens designing with a shorter accessible focal length or a thinner lens with a given focal length. Good agreement between the experiment and calculation for the THz beam profile confirms that dolomite has high homogeneity as a lens material, suggesting the possibility of using natural stones for THz optical elements.

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