Optically Tunable Ultrafast Broadband Terahertz Polarimetric Device Using Nonvolatile Phase‐Change Material

Actively tunable ultrafast broadband terahertz (THz) polarimetry using a reconfigurable phase‐change material holds great potentials and prospects for the achievement of next‐generation versatile integrated THz components and systems in a variety of THz applications. Here, an optically tunable ultrafast broadband THz polarimetric device (THz‐PoD) composed of a phase‐change material Ge 2 Sb 2 Te 5 (GST) and a thin mica substrate is demonstrated. This proposed novel THz‐PoD is verified for a frequency range of 0.1–2.5 THz, exhibiting broadband and ultrafast determination of polarization states for linearly polarized THz waves at polarization angles from −90° to 90°. It is shown that optical excitation with ns pulses allows easy and efficient control of the polarimetric properties of such THz‐PoD. The essential role of the GST film in switching the phase transition between the amorphous and crystalline phases is emphasized by the theoretical investigation of the optically tunable ultrafast polarimetric mechanism of the device. This phase transition allows optically changing the THz‐PoD's properties by ns‐pulsed laser in a controlled way to achieve THz polarimetry for linearly polarized THz waves. The combined advantages of this strategy can open up a new and promising way for realizing versatile reconfigurable and integrated THz devices, which may further promote the development of novel THz systems and applications.