Dynamically tunable multiple-polarization-sensitive black phosphorus metasurface detector operating in the mid-infrared region

Polarization-sensitive photodetection plays a critical role in various applications. In this work, we propose a dynamically tunable black phosphorus (BP) photodetector integrated with a Ge₂Sb₂Te₅ (GST225) plasmonic metasurface for mid-infrared polarized light detection. The detector features a chiral gold array within the metasurface, enabling both linear and circular polarization responses. By modulating the crystallization fraction of GST225, the circular dichroism (CD) peak wavelength can be tuned from 3.86 μm to 4.59 μm, while adjusting the gold array geometry further extends the tunable CD peak range from 3.42 μm to 4.71 μm. Within this range, CD and linear dichroism (LD) values exceed 0.4 and 0.42, respectively, under normal incidence. The detector maintains a stable polarization response across varying incident angles. Electrical analysis confirms that the BP layer exhibits distinct photocurrent responses to different polarization states, including left-handed circularly polarized (LCP), right-handed circularly polarized (RCP), and linearly polarized light along the x- (L_x) and y-axes (L_y). With its tunable polarization selectivity and robust performance, the proposed metasurface photodetector is highly promising for mid-infrared applications in sensing, imaging, and quantum computing and communication.