Review of Anisotropic Terahertz Material Response

Abstract

Anisotropy is ubiquitous in solids and enhanced in low-dimensional materials. In response to an electromagnetic wave, anisotropic absorptive and refractive properties result in dichroic and birefringent optical phenomena both in the linear and nonlinear optics regimes. Such material properties have led to a diverse array of useful polarization components in the visible and near-infrared, but mature technology is non-existent in the terahertz (THz). Here, we review several novel types of anisotropic material responses observed in the THz frequency range, including both linear and circular anisotropy, which have long-term implications for the development of THz polarization optics. We start with the extreme linear anisotropy of macroscopically aligned carbon nanotubes, arising from their intrinsically anisotropic dynamic conductivity. Magnetically induced anisotropy will then be reviewed, including the giant Faraday effects observed in semiconductors, semimetals, and two-dimensional electron systems.Comment: 26 pages, 11 figure

Modifying the polarization state of terahertz radiation using anisotropic twin-domains in LaAlO_3

“…determining justñ xx ). Other systems exhibiting anisotropy in the THz range have been reviewed recently [19][20][21].…”

Layer Caused an Anisotropic Terahertz Response of a 3D-printed Simulative Shale Core

“…11 In our previous study, we modeled the oil shale samples as a uniaxial birefringent medium, and discussed the organic matter-dependent n anisotropy. 23 Here in this work, the effect of the layer structure is investigated. The refraction of the ray at the interfaces is believed to be the source of anisotropy, which was never considered in previous studies.…”

“…Various crystals and alternating structures have been studied to exhibit THz birefringence. 23 In our previous work, 24 anisotropic responses of oil shales were initially studied by THz-time domain spectroscopy (THz-TDS).…”

A table-top, repetitive pulsed magnet for nonlinear and ultrafast spectroscopy in high magnetic fields up to 30 T

“…The optical access via interchangeable windows allows us to introduce a variety of wavelengths, and, importantly, the application most suited for this magnet will be time-domain terahertz spectroscopy [7][8][9][10][11][12][13][14][15] because of the compact design and direct optical access to the sample. Furthermore, the direct optical access allows polarizationsensitive measurements 14,44 without the complications that arise with optical fibers. Finally, the mini-coil design can be reproduced by other researchers around the world and incorporated into setups that already use expensive ultrafast laser systems or other sophisticated optical systems, greatly expanding the availability of high magnetic fields for condensed matter and materials research.…”