Switchable broadband-to-narrowband terahertz metamaterial absorber based on phase-change material GST

Abstract

Leveraging the non‐volatile phase‐change characteristics of Ge2Sb2Te5 (GST), we design and numerically verifies a terahertz metamaterial absorber that enables dual‐function switching between broadband and narrowband absorption in different terahertz frequency bands. The absorber consists of a top gold‐GST hybrid resonant layer, a middle polymethacrylimide (PMI) dielectric layer, and a bottom gold reflector. Simulation results show that when GST is in the amorphous state (a‐GST), the device exhibits a narrowband absorption peak at 9.39 THz with an absorptivity of 97.60%, a quality factor (Q) of 13.14, and a sensitivity (S) of 809 GHz RIU−1, making it suitable for refractive‐index sensing. When GST is in the cubic crystalline state (c‐GST), the device achieves over 90% absorptivity in the frequency range of 3.31–7.63 THz, corresponding to an absorption bandwidth of 4.32 THz (relative bandwidth 78.98%), and near‐unity absorptivity at 3.81 THz and 6.87 THz. Compared with most reported absorbers based on volatile phase‐change materials (VO2 and graphene), our design employs non‐volatile GST, which can stably maintain its absorption state after the external excitation is removed, thus significantly reducing static power consumption. Moreover, the broadband absorption bandwidth (4.32 THz) of our design is relatively wide among similar switchable absorbers. The absorber also features polarization insensitivity and wide‐angle stability, showing potential in terahertz communication, imaging, detection, and sensing applications.