Ultrafast Saturable Absorption of Core/Shell Colloidal Quantum Dots |
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| Authors: | Jingzhou Li Saifeng Zhang Hongxing Dong Yunfei Ma Bin Xu Jun Wang Zhiping Cai Zhanghai Chen Long Zhang |
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| Institution: | 1. Key Laboratory of Materials for High‐Power Laser, Shanghai Institute of Optics and Fine Mechanics, Chinese Academy of Science, Shanghai, China;2. University of Chinese Academy of Sciences, Beijing, China;3. Laboratory for Advanced Materials, Department of Chemistry, East China University of Science and Technology, Shanghai, China;4. Department of Electronic Engineering, Xiamen University, Xiamen, China;5. State Key Laboratory of Surface Physics and Department of Physics, Fudan University, Shanghai, China;6. IFSA Collaborative Innovation Center, Shanghai Jiao Tong University, Shanghai, China |
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| Abstract: | Ultrafast saturable absorption (SA) materials that are capable of blocking the optical absorption under strong excitation have extensive applications in photonic devices. This work presents core/shell colloidal quantum dots (CQDs) which have the quantized energy levels, excellent band gap tunability, and possess significant SA performance. When the band gap is close to the pump pulse energy, the CQDs show significant resonant SA response. At the same excitation conditions, the core/shell CQDs dispersions show better SA response than graphene dispersions, and comparable to the recently reported molybdenum disulfide. The carrier dynamics of the SA of the CQDs is analyzed systematically. The research has also found that the two‐photon absorption of the CQDs show nearly cubic power law of the band gap, while the SA performance keeps almost the same in the nonresonant regime. Further, superior passive Q‐switched laser behavior is observed using the CQDs as a saturable absorber. The results directly reveal the physical processes of this basic problem and broaden the applications of CQDs in photonic devices. |
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| Keywords: | colloidal quantum dots nanophotonics nonlinear optics Q‐switched quantum confinement effects saturable absorption |
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