Extremely Polarized and Efficient Hot Electron Intraband Luminescence from Aluminum Nanostructures for Nonlinear Optical Encoding

Hot electron intraband luminescence from plasmonic nanostructures is of critical importance for integrated photonic devices and applications in ultracompact nanospectrometer, bioimaging, information encryption et al. Although, the past few decades have witnessed tremendous progress in enhancing the luminescence efficiency of plasmonic nanostructures, the luminescence is usually unpolarized or partially polarized and difficult to be tailored because of its incoherent and broadband feature, significantly limiting its applications. Here the current limitation, demonstrating extremely polarized hot electron intraband luminescence with record‐high degree of linear polarization (≈1) and ≈40 000‐fold enhancement from judiciously designed aluminium (Al) plasmonic nanostructures, is broken through. The designed nanostructures exhibit strong polarization‐dependent anisotropic scattering across the visible band which efficiently modulates the luminescence in orthogonal directions. Leveraging this appealing feature, high‐contrast analyzer controlled optical image encryption and camouflage for information security applications are demonstrated. This research lays the groundwork for integrated nonlinear photonic devices based on complementary metal–oxide–semiconductor (CMOS)‐compatible plasmonic materials and paves the way for ultracompact on‐chip photonic devices demanding polarized white light sources. Extremely polarized nanoscale white light sources with record‐high degree of linear polarization (≈1) and ≈40 000‐fold enhancement are demonstrated by hot electron intraband luminescence from metal–insulator–metal aluminium plasmonic nanostructures. This holds great promise for nonlinear optical image encoding and integrated photonic devices where broadband and polarized light sources are demanded.