Terahertz Devices Using the Optical Activation of GeTe Phase Change Materials: Toward Fully Reconfigurable Functionalities

Abstract

Multifunctional terahertz (THz) devices are crucial for the development of practical applications such as high-speed communications, spectroscopy, and imaging, but their expansion is still requiring efficient agility functions operating in the THz domain. Chalcogenide phase change materials (PCMs) with broadband responses and nonvolatile and reversible transitions between dielectric and metal-like phases were successfully investigated as agile elements in photonics or electronics applications, but their potential for controlling the THz waves is still under evaluation. We are demonstrating the optical control of specific states of the germanium telluride (GeTe) PCM and its integration as a control element for enabling future optically reconfigurable THz devices. The excellent contrast of the material's THz properties in the two dissimilar states was used for optical-induced modulation of THz resonances of a metamaterial based on split-ring-resonator metallic structures integrating GeTe patterns. We experimentally confirm for the first time the feasibility of all dielectric GeTe-based THz polarizers, presenting broadband responses, high extinction ratios when the GeTe is in the metal-like phase, and almost transparency when amorphous. This highly functional approach based on optically controlled multioperational THz devices integrating PCMs is extremely stimulating for generating future disruptive developments (field-programmable metasurfaces, dielectric coding metamaterials) with multifunctional capabilities for THz waves manipulation.

Terahertz Metamaterials for Free-Space and on-Chip Applications: From Active Metadevices to Topological Photonic Crystals

“…(e) Temperature-controlled optical activity and negative refractive index [33]. (f) Active metadevices integrated with GeTe [34]. temperature of the metadevice, which leads to the change of circular birefringence from 70 °to 0 °and circular dichroism from 0.6 to 0.…”

“…Germanium telluride (GeTe) is another commonly adopted PCM in the terahertz regime with a nonvolatile feature whose electrical and optical properties can be changed at a nanosecond timescale by thermal, electrical, or optical stimuli [34]. The dynamic responses of a hybrid metallic metadevice integrated with GeTe were demonstrated with a remarkable frequency shift from 0.58 THz to 0.73 THz.…”

“…(e) Temperature-controlled optical activity and negative refractive index[33]. (f) Active metadevices integrated with GeTe[34].…”

Reconfigurable and Nonvolatile Terahertz Metadevices Based on a Phase-Change Material

“…These attractive properties make PCMs an extremely promising platform for active photonic and plasmonic applications. Among the PCM family, the germanium–antimony–telluride alloy (GeTe) x -(Sb2Te3) 1– x (GST) is a popular choice owing to its high switching speed, long retention time, and large number of recoverable write–erase cycles, which has been widely adopted for tunable nanophotonic devices from the infrared to ultraviolet regions. − In recent years, some preliminary studies on PCMs, such as GST-225 − and GeTe − for dynamic THz wave manipulation with nonvolatility, have been reported. However, the centimeter-level area reversible modulation and electrical-pulse switching properties of GST-based THz devices remain largely unexplored, which are critical to the realization of functional and integrated chip-scale THz modulators.…”

Tunable Terahertz Wavefront Modulation Based on Phase Change Materials Embedded in Metasurface

“…In recent years, metasurfaces combined with phase change materials (PCMs) to achieve dynamic photonic devices have become a research hotspot [ 15 , 16 ]. Phase change material (PCM) is a promising and earth-abundant alternative to the next-generation nonvolatile optical devices, offering a new avenue to realize tunable wavefront manipulation.…”