Integrated sub-terahertz waveguide reconfigurable attenuator based on Ge$_2$Sb$_2$Te$_5$ phase-change material

The use of chalcogenide semiconductor compounds, in particular the Ge–Sb–Te material with phase memory, is of great importance for the further development of terahertz micro- and nanoelectronics, including the creation of spatiotemporal terahertz modulators for high-speed wireless communications, elements of neuromorphic photonics, metamaterials for machine learning, as well as plasmonic devices and applications that provide data storage with the possibility of their subsequent reconfiguration. In this paper, we study the change in the signal passing through the terahertz waveguide depending on the phase state of the Ge–Sb–Te thin film covering the waveguide. In this work, two versions of waveguides were manufactured: unclad and based on an effective medium. The phase memory material was used to control the parameters of the transmitted signal. During the experiments it was found that the value of the absorption contrast between the amorphous and crystalline states of Ge–Sb–Te exceeds 10 dB for the case when the orientation of the electric field vector of the wave propagating along the waveguide is perpendicular to the Ge–Sb–Te layer. The obtained results open up the possibility of using the developed elements as reconfigurable attenuators in the creation of integrated terahertz photonics devices.