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.

Terahertz spectroscopy of natural stone materials

“…1 Measured refractive indexes and extinction coefficients of stones in frequency range from 0.2 to 1.2 THz. [3] interference term. From Eq.…”

“…From Eq. 1, we obtained the refractive index and the extinction coefficient by using the method described in other papers [3,4]. We conducted X-ray diffraction measurement to investigate the relationship between the THz optical constants and constituent minerals of the rocks.…”

Tutorial: Terahertz beamforming, from concepts to realizations

“…This allows coaxial configurations comprising both optical and terahertz waves. 83 Additional to the dielectrics previously mentioned, there are a few examples of slightly more exotic materials being used for this purpose, including natural stone, 84 as shown in Fig. 7(a), which was 4.1 mm thick, and focused to a distance of ∼95 mm over a frequency range from 0.2 to 0.7 THz.…”

Strong optical phonon mode of natural seraphinite probed by terahertz time-domain spectroscopy

“…of seraphinite are obtained from the transmission amplitude spectrum and spectral phase difference [6].…”

“…Experiments were conducted by a conventional THz-TDS to obtain the index of refraction and the extinction coefficient [6].…”