A Universal Strategy for Polarization-Sensitive Sub-Bandgap SWIR Photodetectors Enabled by Plasmonic Quasi-Bound States in the Continuum: Demonstration with Isotropic MoTe ₂

Polarization-sensitive short-wave infrared (SWIR) photodetection is critically important for imaging, telecommunications, and integrated photonic technologies. However, polarization-sensitive two-dimensional (2D) photodetectors are typically limited to a narrow range of intrinsically anisotropic materials, which suffer from poor polarization discrimination, environmental instability, and bandgap-limited photoresponse in the SWIR region. Here, we take molybdenum ditelluride (MoTe 2 ) as a representative 2D semiconductor and overcome its bandgap and isotropic limitations by utilizing plasmonic quasi-bound states in the continuum (quasi-BICs). By precisely controlling the rotation angle between paired metallic nanorods to intentionally break symmetry, plasmonic quasi-BICs are excited, giving rise to strongly anisotropic sub-bandgap SWIR absorption in the metallic nanostructures with a polarization ratio of ∼7. Through integration with few-layer MoTe 2, the device achieves a high photocurrent polarization ratio of 3.2 at the wavelength of 1.72 μm, surpassing the intrinsic photoresponse range of MoTe 2 . Photocurrent mapping images confirm the key role of the asymmetrically configured plasmonic metasurface in photocurrent generation. Finally, polarization-coded telecommunication and high-resolution SWIR polarized imaging are demonstrated, highlighting the strong potential of the device. This work presents a universal strategy for polarization-sensitive SWIR photodetection that overcomes the intrinsic photoresponse and isotropic limitations of 2D materials, paving the way toward next-generation multifunctional photodetectors.