Highly Efficient Active All-Dielectric Metasurfaces Based on Hybrid Structures Integrated with Phase-Change Materials: From Terahertz to Optical Ranges

Abstract

Recently, all-dielectric metasurfaces (AMs) have emerged as a promising platform for high-efficiency devices ranging from the terahertz to optical ranges. However, active and fast tuning of their properties, such as amplitude, phase, and operating frequency, remains challenging. Here, a generic method is proposed for obtaining high-efficiency active AMs from the terahertz to optical ranges by using "hybrid structures" integrated with phase-change materials. Various phase-change mechanisms including metal−insulator phase change, nonvolatile phase change, and ferroelectric phase change are investigated. We first experimentally demonstrate several high-efficiency active AMs operating in the terahertz range based on hybrid structures composed of free-standing silicon microstructures covered with ultrathin phase-change nanofilms (thickness d ≪ λ). We show that both the frequencies and the strength of the Mie resonances can be efficiently tuned, resulting in unprecedented modulation depth. Furthermore, detailed analyses of available phase-change materials and their properties are provided to offer more options for active AMs. Finally, several feasible hybrid structures for active AMs in the optical range are proposed and confirmed numerically. The broad platform built in this work for active manipulation of waves from the terahertz to optical ranges may have numerous potential applications in optical devices including switches, modulators, and sensors.

All‐Dielectric Metamaterial Fabrication Techniques

“…For example, our group recently designed a highly efficient active all-dielectric metasurfaces, as shown in Figure 7c, based on DRIE technology. [92] By using this method, an all-dielectric metasurface with "hybrid structures" is obtained, and can be applied in ranges from terahertz to optic. Laser micromachining combines mechanical and optical technologies to etch high-quality micro/nanostructures from many materials, and is usually used to define the surface shape of a silicon or quartz material.…”

Tunable nanophotonics enabled by chalcogenide phase-change materials

“…The crystallization process was carried out through slow heating of GeTe above its crystallization temperature (∼ 200°C). More recently, several innovative hybrid MSs for active manipulation of fundamental resonance modes of constituent metaatoms through the phase transition of embedded PCMs have been proposed [163][164][165][166].…”

All-dielectric concentration of electromagnetic fields at the nanoscale: the role of photonic nanojets

“…The phase transition of LCs is not the only way to tune the properties of PNJs, but any other methods that modify the index distribution would work as well. For instance, phase change materials [79][80][81][82][83] switch from their amorphous state to their crystalline state and vice versa. This provides a binary tuning of the index contrast.…”