Bandgap Gradient Nanowire Photodetectors for Logic Gates and Encrypted Optical Communication

The rapid development of optoelectronic devices presents growing challenges to information confidentiality and security. A gradient structure, capable of transmitting optical signals dependent on the incident light, is highly attractive for applications in logical operations, image sensing, and secure optical communication. In this study, composition/bandgap gradient CdS_1-xSe_x nanowires were synthesized using a magnet-pulling source-moving chemical vapor deposition method and fabricated into high-performance photodetectors. Structural characterizations and optical investigations indicate that these band gap-gradient CdS_1-xSe_x nanowires exhibit high crystalline quality with continuously tunable PL emissions from green to red. Bandgap-gradient CdS_1-xSe_x nanowire photodetectors were fabricated, and their performance is remarkable in terms of a high I_on/I_off ratio of 10³, high responsivity of 89 A/W, high detectivity of 1.06 × 10¹³ Jones, and good switch characteristics. Additionally, optical-controlled "AND" and "OR" photoelectric logic gates are successfully implemented based on these gradient nanowire photodetectors. Finally, the single- and dual-channel optical communication systems are designed and constructed to show the applications in the security and encryption of optical communication. All of these findings highlight the potential of combining on-nanowire bandgap modulation with advanced technology and provide an effective avenue for developing multifunctional systems based on nanophotonic devices.