Dual-Polarity Dember Photodetectors for Optical Encryption Communications

Optical wireless communication has garnered significant interest, yet its inherent transparency poses a formidable challenge to ensure communication security. Optical encryption communication (OEC) emerges as a potential remedy; however, its widespread adoption is hindered by its intricate design and high operational complexity. Herein, we propose an OEC scenario employing self-powered dual-polarity Dember photodetectors (PDs) composed by a sandwich configuration of ITO/MASnI3/Ag. The highly manipulated photonic responses (i.e., direct optical absorption and localized surface plasmon resonance) together with the strong Dember effect by perovskite material empower the unbiased PDs to exhibit the reverse photocurrents (i.e., dual polarity) across a broad wavelength band, which shows a strong robustness against the variations of light source, material composition, and geometric setup. Moreover, the dual-polarity PDs show exceptionally high performances, i.e., an ultrahigh responsivity of 114.2 A/W, a large specific detectivity of 2.4 × 1012 Jones, and an ultrashort response time of ∼2.2 ns. Furthermore, we employ the dual-polarity PD as the receiver to establish a compatible OEC system, where the light components at wavelengths of 302 and 706 nm are taken as the main signal and secret key, respectively. A series of ASCII codes is encoded into the main signal and transmitted through the light and then successfully decoded on the receiver side by using the dual-polarity PD. It is verified that the information can be better encrypted with the introduction of the dual-polarity Dember PD. The study provides a promising approach for secure and high-performance optical communication through the integration of the newly developed PDs.