title: Terahertz lens made out of natural stone.
abstract: 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.
authors: Daehoon
authors: D
authors: Han
authors: Kanghee
authors: K
authors: Lee
authors: Jongseok
authors: J
authors: Lim
authors: Sei Sun
authors: SS
authors: Hong
authors: Young Kie
authors: YK
authors: Kim
authors: Jaewook
authors: J
authors: Ahn