Abstract
We report the ultra-broadband nonlinear optical (NLO) response of Bi2TexSe3−x nanosheets produced by a facile solvothermal method. Our result show that the extracted basic optical nonlinearity parameters of Bi2TexSe3−x nanosheets, αNL, Imχ(3), and FOM reach ~104 cm/GW, ~10−8 esu and ~10−13 esu cm, respectively, which are several orders of magnitude larger than those of bulk dielectrics. We further observed the excitation intensity dependence of the NLO absorption coefficient and the NLO response sensitivity. The mechanisms of those phenomena were proposed based on physical model. The wavelength dependence of the NLO response of Bi2TexSe3−x nanosheets was investigated, and we determined that the Bi2TexSe3−x nanosheets possess an ultra-broadband nonlinear saturable absorption property covering a range from the visible to the near-infrared band, with the NLO absorption insensitive to the excitation wavelength. This work provide fundamental and systematic insight into the NLO response of Bi2TexSe3−x nanosheets and support their application in photonic devices in the future.
Highlights
Topological insulators (TIs) are electronic materials that exhibit an insulation state for their bulk but a conduction state on their edge and surface[1,2,3,4]
The morphology of the as-prepared Bi2TexSe3−x nanosheets was characterized by scanning electron microscopy (SEM), atomic force microscopy (AFM) and transmission electron microscopy (TEM)
Our results demonstrate that the Bi2TexSe3−x nanosheets exhibit ultra-broadband saturable absorption properties and possess fascinating nonlinear optical (NLO) parameters, i.e., αNL ~ −1 04 cm/GW, Imχ(3) ~ 10−8 esu, and figure of merit (FOM) ~ 10−13 esu cm
Summary
Topological insulators (TIs) are electronic materials that exhibit an insulation state for their bulk but a conduction state on their edge and surface[1,2,3,4]. Similar work on other members of the Bi2TexSe3−x family, i.e., Bi2Te3, Bi2TeSe2, and Bi2Te2Se24–28, was reported Those works generally focused on the modulation depth, saturation intensity and nonsaturable loss. Those are necessary indicators for the application of saturable absorbers, investigation into the basic NLO parameters, such as the NLO absorption coefficient αNL and third-order NLO susceptibility Imχ(3), has been limited. Those basic coefficients are important optical parameters for 2D TIs, which determine the performance of 2D TIs-based nanophotonic devices. It was found that atom-doped Bi2TexSe3−x nanosheets (Bi2TeSe2, Bi2Te2Se) showed a more sensitive nonlinear absorption response to photoexcitation
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