Tailored Metal-Oxygen Bonding in Amorphous Perovskite CoSnO3 for Broadband Ultrafast Laser State Active Manipulation

Abstract

Amorphous perovskite CoSnO₃ has attracted significant attention due to its unique properties and various modification methods. However, modifying metal-oxygen bonds on the nonlinear optical (NLO) characteristics remains uncharted. In this study, a dehydration method is employed to convert the metal-hydroxyl bonds (M─OH) of hydroxide CoSn(OH)₆ into metal-oxygen bonds (M─O), successfully preparing amorphous CoSnO₃ with oxygen vacancies. Subsequently, effective regulation of the metal-oxygen bonds in amorphous CoSnO₃ is achieved through an ion exchange strategy, yielding Fe-doped CoSnO₃ (Fe-CoSnO₃). Comprehensive characterization and analysis revealed that the regulation of metal-oxygen bonds accelerated the electron transition rate, resulting in a fast recovery time of ≈245.1 fs for Fe-CoSnO₃, accompanied by a significant boost in broadband NLO properties. Notably, when Fe-CoSnO₃ is utilized as a saturable absorber (SA), it exhibited superior mode-locking characteristics compared to CoSnO₃ in the range of 1–2 µm. Specifically at the communication band of 1.5 µm, the dynamic switching between single-wavelength and dual-wavelength mode-locking operations is achieved. With the ultrafast laser state manipulation, a digital encoding is also demonstrated. This work confirmed that the tailoring of metal-oxygen bonds makes Fe-CoSnO₃ an excellent NLO material for ultrafast optical applications, and this tailoring strategy provides new insights for designing advanced NLO materials.