First‐Principles Insights Into Fe 2 O 3 /In 2 S 3 Heterojunction and Its Application in Dispersion‐Managed Fiber Lasers

ABSTRACT Heterostructure materials have garnered substantial interest across optics, medicine, optoelectronics, and electromagnetics due to their ability to combine advantageous characteristics from multiple constituent phases. Notably, Fe 2 O 3 /In 2 S 3 heterojunctions have demonstrated enhancement mechanisms for both photogenerated charge carrier separation and nonlinear optical response. However, their optoelectronic properties from a theoretical perspective and their potential in ultrafast photonics have not been extensively explored. Herein, robust S─O covalent‐bonded Fe 2 O 3 /In 2 S 3 heterojunctions were successfully synthesized via heat treatment technology. First‐principles calculations were conducted to examine thermal stability, electronic band structures, density of states distributions, electron localization functions, and dielectric responses, thereby establishing a fundamental understanding of intrinsic material properties while informing future optoelectronic implementations. By employing the Fe 2 O 3 /In 2 S 3 heterojunction in a fiber cavity with negative dispersion, passive mode‐locking operation was realized, delivering a pulse width of 300 fs. Moreover, the incorporation of the Fe 2 O 3 /In 2 S 3 heterojunction into a net positive dispersion fiber cavity resulted in the achievement of mode‐locked operation with a pulse duration of 123 fs. Compared with previous studies, these lasers show improved performance. This work advances the understanding of Fe 2 O 3 /In 2 S 3 structure‐property relationships from a theoretical perspective and highlights their potential as promising nonlinear optical materials for advanced optoelectronic devices from an experimental standpoint.