Fiber‐Endface‐Integrated PdSe ₂ /2H‐MoTe ₂ Heterojunction Photodetector for Broadband Linear‐Polarization Detection

ABSTRACT The development of next‐generation optical networks demands miniaturization, polarization discrimination, and broadband operation. Compared to current complex systems with numerous bulky opto‐electro‐mechanical elements arranged in tandem along the optical path, the integration of a polarization‐sensitive detector within optical fiber systems provides a new route for realizing compact polarized optical networks. However, most of these devices cannot be seamlessly integrated with mainstream optical fiber systems. Here, we propose a fiber‐integrated polarimeter by stacking a PdSe ₂ /2H‐MoTe ₂ van der Waals (vdW) heterojunction onto the facet of a standard optical fiber, constructing a high‐performance polarization detector with a responsivity of 25 mA/W, a polarization ratio of approximately 2, and a relatively fast response time of 59 µs at 1550 nm. Additionally, benefiting from the broadband light absorption of PdSe ₂ /2H‐MoTe ₂ heterojunction, the devices demonstrate a broad spectral response range from 532 nm to 1630 nm. Leveraging its intrinsic polarization sensitivity, we demonstrate a polarization‐encoded secure communication scheme. Combining broadband operation, polarization selectivity, and structural simplicity in a fiber‐native form, this work establishes a compact and multifunctional platform for polarization demodulation, monitoring, and secure optical communication in integrated fiber systems.