Electrical tuning of phase-change antennas and metasurfaces

Abstract

The success of semiconductor electronics is built on the creation of compact, low-power switching elements that offer routing, logic, and memory functions. The availability of nanoscale optical switches could have a similarly transformative impact on the development of dynamic and programmable metasurfaces, optical neural networks, and quantum information processing. Phase change materials are uniquely suited to enable their creation as they offer high-speed electrical switching between amorphous and crystalline states with notably different optical properties. Their high refractive index has also been harnessed to fashion them into compact optical antennas. Here, we take the next important step by realizing electrically-switchable phase change antennas and metasurfaces that offer strong, reversible, non-volatile, multi-phase switching and spectral tuning of light scattering in the visible and near-infrared spectral ranges. Their successful implementation relies on a careful joint thermal and optical optimization of the antenna elements that comprise an Ag strip that simultaneously serves as a plasmonic resonator and a miniature heating stage.

On-Chip Integrated Photonic Devices Based on Phase Change Materials

“…Rather, to switch, either electrical means or optical means are used which achieve the temperature required for switching between crystalline and amorphous phases. Although some electro-thermal methods have also been improved recently through the use of devices such as graphene heaters [79], considered as a fundamental mechanism, there is a lag in switching speed [80]. Among these three means of switching, optical switching produces the fastest switching, followed by electrical switching, while thermal switching remains the slowest [19,36].…”

“…One method is to use an external electrical circuit that is generally connected to a heating element that generates heat through resistance to the current [7,87]. Examples of such systems are ITO heaters [88,89], silver heaters [80], and PIN heaters [90]. The other method is the approach used in memristors where current is used for achieving the phase change [7].…”

Intermediate Phase‐Change States with Improved Cycling Durability of Sb2S3 by Femtosecond Multi‐Pulse Laser Irradiation

“…In the visible to ultraviolet range, amplitude modulation becomes the only choice for device operation by exploiting the change of the imaginary part of the complex refractive index, such as color display, [15] reconfigurable dielectric metamaterials, [16] and electrical tuning metasurface. [17] Zhang et al [18] developed Ge-Sb-Se-Te alloys to extend the transparent band to 1 µm by adding Se to increase the bandgap, which, however, is still not large enough for visible and near-infrared wavebands. Other compound PCMs such as sesqui-chalcogenides (e.g., Sb 2 Te 3 ) [19] and tetrelschalcogenides (e.g., GeTe or SnSe 2 ) [20] have also been investigated.…”

Dielectric Metalens: Properties and Three-Dimensional Imaging Applications

“…In particular, metalenses with electrically tunable focal length and focusing efficiency have been in great demand in next-generation three-dimensional imaging applications such as multi-focal near eye displays, holographic displays, and compact depth sensing. Recently, there have been numerous studies on electrically tunable flat optics with advantages in large tunability and diffraction efficiency, such as thermo-optic polymer [ 71 , 72 ], micro-mechanical systems [ 73 , 74 , 75 ], deformable elastomer [ 76 ], twisted nematic liquid crystal [ 77 , 78 , 79 ], and phase-change materials [ 80 , 81 , 82 , 83 ]. For their practical use in ultracompact three-dimensional imaging applications, it seems that an active metalens that guarantees broadband visible range operation with high diffraction efficiency (transparency or reflectivity), and fast switching speed reaching ~kHz would be required.…”