Multi‐Hotspot Nanoantenna‐Mediated PdSe ₂ Long‐Wave Infrared Photodetector with Enhanced Responsivity and Polarization Sensitivity

Long‐wave infrared (LWIR) polarization‐sensitive photodetectors play a pivotal role in widespread applications ranging from spectroscopic sensing to thermal imaging. Traditional bulk LWIR photodetectors suffer from integration challenges due to lattice mismatch and lack of polarization detection capability, as well as high power consumption due to cryogenic cooling requirements. Despite the intrinsic layered lattice structures that ease on‐chip integration and room‐temperature operation, the performance of two‐dimensional (2D) material‐based LWIR photodetectors in terms of responsivity, response speed, and polarization sensitivity still needs further improvement. Here, we propose a distinct paradigm for LWIR photodetectors by synergizing narrow‐bandgap anisotropic 2D PdSe 2 with an H‐shaped multi‐hotspot nanoantenna design. The polarization‐dependent multi‐hotspot plasmon resonance drastically enhances photodetection responsivity and polarization sensitivity without compromising response speed. A responsivity of 1.92 A/W, a response time of ∼40 µs, and a polarization ratio of ∼20 is achieved at 5.6 µm wavelength. High‐contrast polarized LWIR imaging is further demonstrated. Our technology is envisaged to provide a promising approach for high‐performance and multifunctional on‐chip uncooled LWIR photodetectors.