• Acta Physica Sinica
  • Vol. 69, Issue 18, 20200443 (2020)
Ouyang Hao1、2、3, Hu Si-Yang1, Shen Man-Ling1、2、3, Zhang Chen-Xi1, Cheng Xiang-Ai1、2、3, and Jiang Tian2、*
Author Affiliations
  • 1College of Advanced Interdisciplinary Studies, National University of Defense Technology, Changsha 410073, China
  • 2State Key Laboratory of Pulsed Power Laser Technology, Changsha 410073, China
  • 3Hunan Provincial Key Laboratory of High Energy Laser Technology, Changsha 410073, China
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    (a) Schematic diagram of the atomic structure of GeSe2; (b) AFM image of GeSe2 flake by mechanical exfoliation. The thickness of the sample is 88 nm; (c) polarization-dependent Raman spectrum. Four Raman peak positions are at 118, 212, 251, 307 cm–1, respectively; (d)–(g) polar diagrams of the intensity of the four Raman peaks.
    Fig. 1. (a) Schematic diagram of the atomic structure of GeSe2; (b) AFM image of GeSe2 flake by mechanical exfoliation. The thickness of the sample is 88 nm; (c) polarization-dependent Raman spectrum. Four Raman peak positions are at 118, 212, 251, 307 cm–1, respectively; (d)–(g) polar diagrams of the intensity of the four Raman peaks.
    Characterization of anisotropic bands of layered GeSe2 by linear absorption spectrum: (a) Linear absorption spectrum with polarization directions from 0° to 180° with intervals of 15°; (b) the energy band of the 0° polarization direction is determined. The band position obtained indirectly from Tauc’s theorem, where the position of the intersection of the tangent and the abscissa is 2.717 eV; (c) determination of the energy band of the 90° polarization direction. The band position obtained indirectly from Tauc’s theorem, where the position of the intersection of the tangent and the abscissa is 2.7291 eV; (d) anisotropic energy bands of layered GeSe2. The band gap in the b-axis direction is the largest, and the band gap in the a-axis direction is the smallest; (e) polar graph of anisotropic linear absorptivity of layered GeSe2 at 400 nm; (f) polar graph of anisotropic linear absorption of layered GeSe2 at 450 nm.
    Fig. 2. Characterization of anisotropic bands of layered GeSe2 by linear absorption spectrum: (a) Linear absorption spectrum with polarization directions from 0° to 180° with intervals of 15°; (b) the energy band of the 0° polarization direction is determined. The band position obtained indirectly from Tauc’s theorem, where the position of the intersection of the tangent and the abscissa is 2.717 eV; (c) determination of the energy band of the 90° polarization direction. The band position obtained indirectly from Tauc’s theorem, where the position of the intersection of the tangent and the abscissa is 2.7291 eV; (d) anisotropic energy bands of layered GeSe2. The band gap in the b-axis direction is the largest, and the band gap in the a-axis direction is the smallest; (e) polar graph of anisotropic linear absorptivity of layered GeSe2 at 400 nm; (f) polar graph of anisotropic linear absorption of layered GeSe2 at 450 nm.
    Experimental results of superposition state absorption of different polarization directions under 400 nm non-resonant excitation: (a) Results of the I-scan experiment. The circles indicate the experimental data, and the solid lines indicate the excited state absorption curve; (b) polarization-dependent non-linear modulation depth polar plot; (c) polar plot of the change in polarization-dependent linear absorption coefficient α0; (d) polarization diagram of polarization-dependent saturated absorption intensity I1,s; (e) polarization diagram of the polarization-dependent excited state absorption coefficient β0; (f) polarized graph of polarization-dependent saturation light intensity I2,s absorbed by the excited state.
    Fig. 3. Experimental results of superposition state absorption of different polarization directions under 400 nm non-resonant excitation: (a) Results of the I-scan experiment. The circles indicate the experimental data, and the solid lines indicate the excited state absorption curve; (b) polarization-dependent non-linear modulation depth polar plot; (c) polar plot of the change in polarization-dependent linear absorption coefficient α0; (d) polarization diagram of polarization-dependent saturated absorption intensity I1,s; (e) polarization diagram of the polarization-dependent excited state absorption coefficient β0; (f) polarized graph of polarization-dependent saturation light intensity I2,s absorbed by the excited state.
    Experimental results of superposition state absorption of different polarization directions under 450 nm non-resonant excitation: (a) Results of the I-scan experiment. The circles indicate the experimental data, and the solid lines indicate the excited state absorption curve: (b) polarization-dependent non-linear modulation depth polar plot: (c) polar plot of the change in polarization-dependent linear absorption coefficient α0; (d) polarization diagram of polarization-dependent saturated absorption intensity I1,s; (e) polarization diagram of the polarization-dependent excited state absorption coefficient β0; (f) polarized graph of polarization-dependent saturation light intensityI2,s absorbed by the excited state.
    Fig. 4. Experimental results of superposition state absorption of different polarization directions under 450 nm non-resonant excitation: (a) Results of the I-scan experiment. The circles indicate the experimental data, and the solid lines indicate the excited state absorption curve: (b) polarization-dependent non-linear modulation depth polar plot: (c) polar plot of the change in polarization-dependent linear absorption coefficient α0; (d) polarization diagram of polarization-dependent saturated absorption intensity I1,s; (e) polarization diagram of the polarization-dependent excited state absorption coefficient β0; (f) polarized graph of polarization-dependent saturation light intensityI2,s absorbed by the excited state.
    Schematic diagram of GeSe2 based polarized-dependent all-optical switching
    Fig. 5. Schematic diagram of GeSe2 based polarized-dependent all-optical switching
    Polarization/(°)α0/cm–1β0/cm·GW–1I1,s/GW·cm–2I2,s/GW·cm–2δT/%
    03155950815947417.0
    30335935597962387.5
    6036579606972358.2
    9038790663349349.7
    120369725991394368.1
    150340295436629397.3
    1803106249617082417.0
    Table 1.

    Fitting results of I-scan nonlinear superposition state absorption parameters related to 400 nm non-resonant excitation polarization

    400 nm非共振激发偏振相关的I扫描非线性叠加态吸收参数的拟合结果

    Polarization/(°)α0/cm–1β0/cm·GW–1I1,s/GW·cm–2I2,s/GW·cm–2δT/%
    0439091759390634.6
    30496311571258695.6
    606028965409757.1
    906750122188799.9
    1205726681469766.8
    150483451582333685.0
    1804317317610483624.6
    Table 2.

    Fitting results of I-scan nonlinear superposition state absorption parameters related to 450 nm non-resonant excitation polarization

    450 nm近共振激发偏振相关的I扫描非线性叠加态吸收参数的拟合结果

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    Hao Ouyang, Si-Yang Hu, Man-Ling Shen, Chen-Xi Zhang, Xiang-Ai Cheng, Tian Jiang. Polarization-dependent nonlinear optical response in GeSe2[J]. Acta Physica Sinica, 2020, 69(18): 184212-1
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    Received: Mar. 25, 2020
    Accepted: --
    Published Online: Jan. 5, 2021
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