Broadband Graphene-Based Electro-Optic Chiral Polarization Conversion for Terahertz Pulse Shaping

Abstract

Terahertz (THz) radiation is ideally suited for noninvasive testing and short-distance data transmission. Actively controlling the polarization of THz waves is highly desirable in measurement systems. Although significant developments of THz active devices has been achieved through introducing the electromagnetic resonance structure (e.g., metamaterials), the bandwidth is limited. Here, we propose a graphene-based electrically reconfigurable polarization conversion across a broadband THz region (0.3 to 0.9 THz) for controlling the chiral polarization of terahertz pulse. By electrically controlling the graphene conductivity, we can switch the device reflection in-between total internal reflection and metal mirror reflection to realize a frequency-independent phase change, which enables a tunable waveplate with a high dynamic range for manipulating the polarization of THz waves. Because of the frequency-independent modulation property, we achieved tunable chiral polarization THz waveforms in the time domain for the first time, from right-handed to left-handed polarization. This work opens up a new mechanism for designing novel THz modulators for THz circular dichroism.

Quantitative polarization-sensitive super-resolution solid immersion microscopy reveals biological tissues’ birefringence in the terahertz range

“…To realize such a set of linear and elliptical THz-beam polarizations, one can either use classical polarization converters based on the THz birefringent materials (crystalline quartz, sapphire, etc. ), or resort to emerging approaches based on distinct physical effects in graphene 62 , vanadium dioxide 63 , metal-wire grating 64 , multilayer metamaterials 65 , 3D printed conductive polymer structures 66 , and parallel-plate splitters 67 . Third, in the Muller matrix polarimetry, one usually considers interaction between low-aperture beams and a sample, while in the THz SI microscope, one deals with a very wide aperture and excitation of evanescent waves at the SI lens–object interface.…”

“…To realize such a set of linear and elliptical THz-beam polarizations, one can either use classical polarization converters based on the THz birefringent materials (crystalline quartz, sapphire, etc. ), or resort to emerging approaches based on distinct physical effects in graphene 62 , vanadium dioxide 63 , metal-wire grating 64 , multilayer metamaterials 65 , 3D printed conductive polymer structures 66 , and parallel-plate splitters 67 .…”

Ultrawideband Solid-State Terahertz Phase Shifter Electrically Modulated by Tunable Conductive Interface in Total Internal Reflection Geometry

“…Another approach involved a terahertz polarization converter that employed ion-gel gated two graphene layers in the TIR geometry to induce phase changes for both s-and ppolarizations, but the ion-gel device operates at a slow speed and achieves a phase shift of less than 80°. 32 In this study, we propose an ultrawideband phase shifting mechanism utilizing an optically thin conductive layer in the TIR geometry at the interface (referred to as CI-TIR). This approach enables efficient phase modulation of the reflected light while preserving the wideband characteristics for both s-and ppolarizations.…”

Numerical Simulation and Equivalent Circuit Model of Multi-Band Terahertz Absorber Composed of Double-Sided Graphene Comb Resonator Array

“…This type of metamaterials has shown a capability to produce chirality responses such as circular dichroism (CD) [7][8][9][10] or linear dichroism (LD) [10][11][12]. Metamaterials with non-symmetrical geometries have been designed and proposed for different applications such as absorbers [8,12,13], biosensors [14,15], converters [16,17], switches [18,19], and mirrors [6,20] recently showing their versatile possibilities in various the fields of science.…”

“…This distinguishes 2D materials like graphene from the other commonly used materials like metals or dielectrics. Hence it is possible to tune the output spectra of the devices containing graphene without the need to refabricate the devices saving materials, costs, and time [4,6,12,17,[20][21][22][23][24] making them very interesting, especially for spectroscopic applications.…”