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<p>Graphene has led the exploration of nonlinear optical responses in two-dimensional materials with exceptionally strong third-order nonlinearity and its electrical controllability. Nonlinear wave mixing with difference-frequency is particularly interesting in graphene because of the divergent nature of third-order susceptibility as the frequency difference approaches zero, but the study on nearly degenerated four-wave mixing (NDFWM) process in graphene is largely unexplored. In this work, we report the giant third-order susceptibility of monolayer graphene, reaching the order of 10<sup>–13</sup> m<sup>2</sup>&#xa0;V<sup>−2</sup> at the optical telecom C-band via the NDFWM process, and its electrical tunability with a high on–off contrast of 23&#xa0;dB. Moreover, we observed that the NDFWM response under electrical doping exhibits a resonance feature at low pump intensity in ambient conditions, which is substantially altered by varying the pump power. Through non-perturbative quantum master equation calculations, we revealed that our observation is closely related to the dephasing nature of the Dirac fermion of graphene. The decoherence time of photoexcited carriers is estimated up to 70&#xa0;fs at low pump intensity, which regime is not accessible by other nonlinear means such as high harmonic generation requiring high intensity light. Our findings not only pave an unprecedented route for probing nonlinear dynamics of photoexcited carriers across a wide range but also have a significant impact on ultrafast nonlinear information processing in graphene.</p>

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Manipulating nonlinear dephasing dynamics of Dirac fermions in nearly degenerate four-wave mixing

  • 期刊论文

  • 出版模式：

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  • 发表日期：

    2026年6月18日

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  • Seongju Ha,
  • Youngchan Choi,
  • Nam Hun Park,
  • Jungseok Choi,
  • Jaedeok Park,
  • Kwang Jun Ahn,
  • Hee-Su Park,
  • JaeDong Lee,
  • Sang Min Lee,
  • Dong-Il Yeom

摘要

Graphene has led the exploration of nonlinear optical responses in two-dimensional materials with exceptionally strong third-order nonlinearity and its electrical controllability. Nonlinear wave mixing with difference-frequency is particularly interesting in graphene because of the divergent nature of third-order susceptibility as the frequency difference approaches zero, but the study on nearly degenerated four-wave mixing (NDFWM) process in graphene is largely unexplored. In this work, we report the giant third-order susceptibility of monolayer graphene, reaching the order of 10–13 m2 V−2 at the optical telecom C-band via the NDFWM process, and its electrical tunability with a high on–off contrast of 23 dB. Moreover, we observed that the NDFWM response under electrical doping exhibits a resonance feature at low pump intensity in ambient conditions, which is substantially altered by varying the pump power. Through non-perturbative quantum master equation calculations, we revealed that our observation is closely related to the dephasing nature of the Dirac fermion of graphene. The decoherence time of photoexcited carriers is estimated up to 70 fs at low pump intensity, which regime is not accessible by other nonlinear means such as high harmonic generation requiring high intensity light. Our findings not only pave an unprecedented route for probing nonlinear dynamics of photoexcited carriers across a wide range but also have a significant impact on ultrafast nonlinear information processing in graphene.