Graphene controlled Brewster angle device for ultra broadband terahertz modulation

Abstract

Terahertz modulators with high tunability of both intensity and phase are essential for effective control of electromagnetic properties. Due to the underlying physics behind existing approaches there is still a lack of broadband devices able to achieve deep modulation. Here, we demonstrate the effect of tunable Brewster angle controlled by graphene, and develop a highly-tunable solid-state graphene/quartz modulator based on this mechanism. The Brewster angle of the device can be tuned by varying the conductivity of the graphene through an electrical gate. In this way, we achieve near perfect intensity modulation with spectrally flat modulation depth of 99.3 to 99.9 percent and phase tunability of up to 140 degree in the frequency range from 0.5 to 1.6 THz. Different from using electromagnetic resonance effects (for example, metamaterials), this principle ensures that our device can operate in ultra-broadband. Thus it is an effective principle for terahertz modulation.

Unveiling optical in-plane anisotropy of 2D materials from oblique incidence of light

“…However, for normal incidence but in the presence of anisotropy, from Eqs. (11)(12)(13)(14) it is clear that they depend on the light polarization, which has been studied in details for strained graphene [32].…”

“…So, for a stretching along the x−axis (φ = 0°) or the y−axis (φ = 90°), the conductivity component σ xy results zero and, therefore, the reflectance and transmittance can obtained from Eqs. (11)(12)(13)(14). Moreover, it is important to keep in mind that, according to Eqs.…”

Exploiting Total Internal Reflection Geometry for Terahertz Devices and Enhanced Sample Characterization

“…In particular its high electron mobility makes it a favorable material to build modulators and other functional devices with broadband performance and high modulation speed . The conductivity of graphene can be manipulated easily from high‐resistance state to semi‐metal state by applying a gate voltage . Consequently, building on the optical device in Section , we designed an electrical device by putting a graphene field‐effect transistor on top a quartz prism.…”

“…Six of our TIR devices are illustrated in Figure . Noting the sensitivity of devices to the angle of incidence has also led to the design of a graphene/quartz device operating at the Brewster angle for high‐performance THz amplitude and phase modulation …”

Unconventional electromagnetic properties of the graphene quantum dots

“…Unconventional optical properties of graphene in the THz range with frequencies f = 0.5 − 100 THz attract significant attention of many researchers [1][2][3][4][5][6][7]. Interest to the THz waves (T-rays) is motivated by variety of potential applications in medicine, information technology, communication and security.…”