Bipolar Circularly Polarized Photodetector Enabled by Dual-Chiral Heterojunctions for Secure Optical Communications

Abstract Circularly polarized light (CPL) carries intrinsic spin-dependent information that is crucial for optical communication and information encryption. However, conventional CPL photodetectors can only discriminate photon helicity because multidimensional optical information is inevitably compressed into a one-dimensional photocurrent magnitude during photoelectric conversion. Here, we report a broadband bipolar CPL photodiode based on a bias-programmable dual-chiral bulk heterojunction architecture that fundamentally overcomes this limitation. The front and rear heterojunctions selectively respond to ultraviolet–visible (UV–vis) and near-infrared (NIR) light under opposite bias voltages, generating positive and negative photocurrents, respectively. The photocurrent polarity decodes spectral information, while the photocurrent amplitude resolves polarization helicity, enabling multidimensional photon information decoding within a single device. The device achieves detectivities exceeding 1013 Jones and photocurrent dissymmetry factors up to 10–2 across the UV–vis–NIR range. Furthermore, it exhibits electrically tunable synaptic behaviors under optical stimulation. Leveraging these multifunctional features, the device achieves secure free-space optical communication with a bit error rate 3 orders of magnitude lower than that of conventional systems, and enables encrypted face recognition with an accuracy exceeding 95% through a neuromorphic processing framework. This work establishes a unified hardware platform for intelligent, secure, and energy-efficient photonic information processing.