Switching of electromagnetic induced transparency in terahertz metasurface

We demonstrate functional switching of electromagnetic induced transparency (EIT) in terahertz (THz) metasurface. We first simulated and fabricated two metasurfaces that have light difference in their unit cell design. THz time domain spectroscopy of fabricated metasurfaces shows that two metasurfaces have almost similar transmission spectra but one of them possesses EIT while the second does not. To implement functional switching of EIT, we show numerically that characteristics of both metasurfaces can be achieved by a single hybrid metasurface containing a phase change material, Ge2Sb2Te5 (GST). GST has a large contrast in THz material properties in its crystalline and amorphous phases and its phase can be rapidly interchanged by external stimuli. We incorporated GST in the unit cell and show that phase change of GST portion in the metasurface unit cell at a specific location modulates the transmission spectra working as an EIT switch. EIT in the metasurface is attributed to coupling of two opposite phases bright resonance modes supported by the unit cell. The group delay of the transmitted THz radiation indicates that THz wave slows down significantly at EIT frequency. The dynamic interplay between two different responses within a single hybrid metasurface can have applications in biosensors, THz buffers, modulators, and other functional THz communication devices.