Carbon dots with tunable third-order nonlinear coefficient instructed by machine learning

Abstract

Nonlinear optical materials are important in community of telecommunication, light-information storage and photo-dynamic therapy. Here, we show a series of carbon dots (CDs, CDs-1 to CDs-72) fabricated from oxalamide with tunable third-order nonlinear optics (NLO) susceptibility χ(3) and switching behavior. These CDs exhibit a size-dependent effect on third-order nonlinear refractive (NLR) index γ and third-order nonlinear saturable absorption (NLSA) coefficient β. Also. they show the NLO switching behavior as the incident laser energy increasing. With the instruction of machine learning, CDs with tunable χ(3) from 0 to 1.79 × 10−8 esu were synthesized as expected. Among them, CDs-12 show NLRSA behavior with third-order NLO susceptibility χ(3) of 3.59 × 10−10 esu, CDs-24 exhibit NLSA behavior with χ(3) of 3.03 × 10−10 esu and CDs-36 own the best susceptibility χ(3) of 1.79 × 10−8 esu with NLO switching behavior.