Real-time two-dimensional beam steering with gate-tunable materials: a theoretical investigation

Abstract

A leaky-wave antenna is proposed that furnishes two-dimensional (2-D) beam scanning in both elevation and azimuth planes via electrical control in real time, and at a single frequency. The structure consists of a graphene sheet on a metal-backed substrate. The 2-D beam-scanning performance is achieved through the proper biasing configuration of graphene. Traditional pixel-by-pixel electrical control makes the biasing network a huge challenge for chip-scale designs in the terahertz regime and beyond. The method presented here enables dynamic control by applying two groups of one-dimensional biasing on the sides of the sheet. They are orthogonal and decoupled, with one group offering monotonic impedance variation along one direction, and the other sinusoidal impedance modulation along the other direction. The conductivity profile of the graphene sheet for a certain radiation angle, realized by applying proper voltage to each pad underneath the sheet, is determined by a holographic technique and can be reconfigured electronically and desirably. Such innovative biasing design makes real-time control of the beam direction and beamwidth simple and highly integrated. The concept is not limited to graphene-based structures, and can be generalized to any available gate-tunable material system.

Fabry-Perot Cavity Leaky Wave Antennas with Tunable Features for Terahertz Applications

“…Leaky-wave phenomena occur at any frequency range. For this reason, LWAs working at THz frequencies are feasible and some examples of devices are already present in the scientific literature [15,[27][28][29][30][31][32][33][34][35][36][37][38][39][40][41][42][43][44]. In this section, only LWAs working in the frequency band between 300 GHz and 3 THz are discussed.…”

Recent Progress on Graphene-Functionalized Metasurfaces for Tunable Phase and Polarization Control

“…Figure 7e is a simplified design to achieve such functionality. The dynamic bean scanning in both elevation and azimuth planes is achieved by applying two groups of one-dimensional biasing pads underneath the graphene sheet [74]. They are orthogonal and decoupled.…”

“…( f ) Radiation pattern in different directions via simulation by simply changing the two groups of biasing voltages. Reproduced with permission from [74], Copyright Optical Society of America, 2016.…”

Electrically Tunable Metamaterials Based on Multimaterial Nanowires Incorporating Transparent Conductive Oxides

“…One of the major limitations of the traditional metamaterial designs is that their optical response is fixed once fabricated, tying them to a specific application and operating wavelength for which they are designed. In order to overcome this limitation, an immense effort has been put on the post-fabrication control of these structures through various mechanisms including mechanical reconfiguration 14 , 15 , utilizing phase change materials (PCMs) 16 , 17 , and using electro-optical materials such as liquid crystals 18 , 19 , low-dimensional graphene 20 , 21 and transparent conducting oxides 22 , 23 . Such mechanisms can allow for tuning the performance of optical devices, serving multiple functionalities, as well as multispectral and broadband operation.…”

“…The surface conductivity of a graphene sheet can be tuned by applying a gate voltage. This effect has been exploited to create flat tunable gradient index metamaterials for manipulation of surface plasmon polariton (SPP) waves in the mid-infrared and far-infrared frequency regimes 21 . Furthermore, the integration of graphene into metasurfaces has allowed for spectrally tunable absorption 20 and modulation of reflection phase at a single frequency which comes at the cost of low amplitude efficiency 24 .…”