Abstract-Reconfigurable Terahertz Devices Using the Optical Activation of GeTe Phase Change Materials

 

Maxime Pinaud, Georges Humbert, Sebastian Engelbrecht, Lionel Merlat, Bernd Fischer, Aurelian Crunteanu

https://arxiv.org/abs/2103.04395

We are demonstrating the optical control of a specific state of the germanium telluride (GeTe) phase change material and its integration as control element for realizing extremely efficient optically reconfigurable THz devices. The excellent contrast of the material THz electrical properties in the two dissimilar states were used for optical-induced fast modulation of THz resonances of a hybrid metamaterial based of arrays of split ring resonator metallic structures integrating GeTe patterns. We experimentally confirm for the first time the feasibility to develop all dielectric (metal free) GeTe-based THz polarizers presenting a broadband response, a high extinction ratio when the GeTe is in the metal-like phase (up to 16.5 dB) and almost transparent when the material is in the amorphous phase. The presented highly functional approach based on non-volatile, optically controlled multi-operational THz devices integrating PCMs, is extremely stimulating for generating disruptive developments like field-programmable metasurfaces or all-dielectric coding metamaterials with multifunctional capabilities for THz waves manipulation.

Abstract-Through-substrate terahertz time-domain reflection spectroscopy for environmental graphene conductivity mapping

Applied Physics Letters

 Hungyen Lin,  Oliver J. Burton, Sebastian Engelbrecht, Kai-Henning Tybussek,  Bernd M. Fischer,  Stephan Hofmann

Schematic of the reflection-based THz-TDS to measure the complex conductivity of graphene through the substrate in a nitrogen purge environment.

https://aip.scitation.org/doi/abs/10.1063/1.5135644

We demonstrate how terahertz time-domain spectroscopy (THz-TDS) operating in reflection geometry can be used for quantitative conductivity mapping of large area chemical vapor deposited graphene films through silicon support. We validate the technique against measurements performed using the established transmission based THz-TDS. Our through-substrate approach allows unhindered access to the graphene top surface and thus, as we discuss, opens up pathways to perform in situ and in-operando THz-TDS using environmental cells.

H.L. acknowledges financial support from the EPSRC (Grant No. EP/R019460/1). S.H. acknowledges funding from the EPSRC (Grant No. EP/K016636/1, GRAPHTED). We also thank Dr. Philipp Braeuninger-Weimer for useful discussion. Additional data for this article are available at https://doi.org/10.17635/lancaster/researchdata/336.