UV/IR dual-waveband photodetection and demultiplexing applications enabled by a wide-/narrow-bandgap heterojunction

A wide-/narrow-bandgap heterojunction offers promising potential for developing broadband response, high speed, and highly sensitive photodetectors. By exploiting the different spectral response of these detectors, transmitted data of different wavelengths can be effectively distinguished, making them promising candidates for wavelength division multiplexing to enhance optical communication transmission rates. Herein, we present a facile dual-wavelength demultiplexing strategy based on ZnO/PbSe wide-/narrow-bandgap heterojunction to achieve ultraviolet (UV)-infrared (IR) broadband detection by utilizing the photosensitive/dielectric properties of ZnO along with unique band alignment. The detector demonstrates a continuous photocurrent response in the UV region, while producing transient pulsed photocurrent in the IR region. It is first time reporting response wavelength extension of transient photodetectors from near-infrared (NIR) to mid-infrared (MIR). Additionally, the response bandwidth reaches 2 kHz in the UV and 0.7 MHz in the IR bands. The UV/IR dual-wavelength optical communication tests show the coexistence of transient pulsed and continuous photocurrents. By incorporating different filter modules at the output terminals, the transmitted data at both wavelengths can be extracted simultaneously. This study offers a facile and practical approach for broadband photodetection and wavelength demultiplexing, while also providing a novel route for extending the application of wide-bandgap semiconductors to IR optoelectronic devices.