Absorption enhancement in LWIR detector via waveguide and plasmonic modes engineering

A high-temperature long-wavelength infrared (LWIR) photodetector using a thin InAs/InAsSb type-II superlattice (T2SL) absorber with enhanced optical absorption is demonstrated. The enhancement results from the excitation of planar waveguide and surface plasmon polariton (SPP) modes confined within the absorber and enabled by an adjacent highly doped semiconductor contact (HDSC) layer. While SPP modes contribute near the 10 µm resonance, stronger absorption arises from guided modes between 7 µm and 9 µm. The absorber-HDSC interface provides a large, tunable Fresnel reflection phase due to a lossless Drude-like contrast, despite material losses. This configuration offers superior mode confinement, phase control, and fabrication practicality, enabling efficient absorption in thin photodetectors and advancing subwavelength photonic design.