Ultrafast Responses in Various Conjugated Polymers with Large Optical Nonlinearity
Ultrafast Responses in Various Conjugated Polymers with Large Optical Nonlinearity
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具有大光学非线性的各种共轭聚合物的超快响应
DOI：
10.1142/9789812812964_0001
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发表时间：
1993
期刊：
影响因子：
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通讯作者：
Takayoshi Kobayashi
中科院分区：
文献类型：
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作者：
Takayoshi Kobayashi
通过飞秒泵浦探针光谱研究了许多共轭聚合物、聚二乙炔（PDA）的各种超快非线性光学过程，例如聚[4,6-癸二炔-1,10-二醇 - 双（[（正丁氧基羰基）甲基]氨基甲酸酯）]（PDA-3BCMU）（蓝相）、聚[5,7-十二二炔-1,12-二醇双([(正丁氧基羰基)甲基]氨基甲酸酯)] (PDA-4BCMU)（红相和蓝相）、聚[1,4-双([2,5-双(三氟甲基]苯基)-1,3-丁二炔] (PDA-DFMP)（蓝相）和聚噻吩 (PT)，例如聚(3-甲基噻吩 (P3MT) 和聚(3-十二烷基噻吩)(P3DT) 和聚噻吩亚乙烯基 (PTV) 还研究了红相 PDA-4BCMU 的皮秒发光光谱。100-fs 泵浦脉冲光生的自由 1Bu 激子到准热自俘获 (ST) 激子的几何弛豫在 PDA 和 100-150 fs 的时间常数下发生。 PT 中 ST 激子的寿命为 70-100 fs，PDA-3BCMU 中 ST 激子的寿命为 2.0±0.1 ps (1.5±0.1 ps)，PDA-4BCMU 中为 3.0±0.3 ps (2.1±0.2 ps)，PDA-4BCMU 中 ST 激子的寿命为 800±100 fs (800±100 fs)。 P3MT.ST激子的衰变动力学通过ST激子和基态的两条电势曲线之间的电势交叉和隧道效应来解释，极弱的温度依赖性表明ST激子和基态之间的势垒的激活过程在ST激子的无辐射弛豫中并不占主导地位。然而，它可以用分形维数中的随机游走来描述。通过应用分形维数模型，确定光谱维数在 0.50 至 0.85 之间，在飞秒分辨光谱中还观察到了由几种非线性光学过程（即烧孔、拉曼增益和动态斯塔克效应）引起的光谱变化，并根据观察到的光谱变化确定了这些非线性过程的三阶磁化率，例如激子跃迁处的吸收饱和度、拉曼增益和共振克尔效应。对应于蓝相 PDA-3BCMU 流延膜和 P3MT 中的吸收饱和度（烧孔）的值分别为 Im[χ(3)1111(-ω;ω,-ω,ω)] = - 2.6×10-9esu 和 -3.5×10-10esu，对于 ħχ = 1.97 eV 对应于 PDA-3BCMU 和 P3MT 中拉曼增益的三阶磁化率。对于 ħω1=1.97 eV 和 ħω2=1.79 eV，P3MT 分别确定为 Im[χ(3)(-ω2;ω2,-ω1,ω1)] = -5.8×10-10esu 和 -1.5×10-10esu。 |Δχ(3)1111(-ω2;ω2,-ω1,ω1)-Δ(3)1122(-ω2;ω2,-ω1,ω)|= 3.9×10-11esu 确定为 ħω1= 1.97 eV 和 ħω2=1.88 eV。
By femtosecond pump-probe spectroscopy various ultrafast nonlinear optical processes were studied for many conjugated polymers, polydiacetylene (PDAs) such as poly[4,6-decadiyne-1,10-diol - bis([(n-butoxycarbonyl)methyl] urethane)](PDA-3BCMU)(blue-phase), poly[5,7-dodecadiyne-1,12-diol bis([(n-butoxycarbonyl)methyl]urethane)] (PDA-4BCMU) (red- and blue-phases), poly[1,4-bis([2,5-bis(trifluoromethyl]phenyl)-1,3-butadiyne] ( PDA-DFMP)(blue-phase), and polythiophenes (PTs) such as poly(3-methylthiophene (P3MT) and poly(3-dodecylthiophene)(P3DT), and polythienylenevinylene)(PTV). Picosecond luminescence spectroscopy was also studied for PDA-4BCMU in red phase.Geometrical relaxation of free1Bu excitons photogenerated by 100-fs pump pulses to the quasithermal self-trapped (ST) excitons takes place with time constants of 100-150 fs in PDAs and 70-100 fs in PTs. The lifetimes of the ST excitons at 10 K (290 K) were 2.0±0.1 ps (1.5±0.1 ps) in PDA-3BCMU, 3.0±0.3 ps (2.1±0.2 ps) in PDA-4BCMU, and 800±100 fs (800±100 fs) in P3MT. The decay kinetics of the ST exciton were explained by potential crossing and tunneling between two potential curves of the ST exciton and the ground state. The extremely weak temperature dependence indicates that the activation process over the potential barrier between the ST exciton and the ground state is not dominant in the radiationless relaxation of the ST exciton. The relaxation dynamics of fluorescence from the PDA-4BCMU film cannot be represented by a single exponential decay; however, it can be described in terms of a random walk in the fractal dimension. By applying the fractal dimension model, the spectral dimension was determined to be between 0.50 and 0.85. The spectral change due to several nonlinear optical processes, i.e. hole burning, Raman gain, and dynamic Stark effect, were also observed in femtosecond resolved spectra. The third-order susceptibility was determined for these nonlinear processes, such as absorption saturation at the exciton transition, Raman gain, and resonant Kerr effect from the observed spectral change. The third-order susceptibility corresponding to absorption saturation (hole burning) in blue-phase PDA-3BCMU cast film and in P3MT was obtained as Im[χ(3)1111(-ω;ω,-ω,ω)] = - 2.6×10-9esu and -3.5×10-10esu, respectively, for ħχ = 1.97 eV. The third-order susceptibility corresponding to the Raman gain in PDA-3BCMU and in P3MT was determined to be Im[χ(3)(-ω2;ω2,-ω1,ω1)] = -5.8×10-10esu and -1.5×10-10esu, respectively, for ħω1=1.97 eV and ħω2=1.79 eV. From the resonant Kerr experiment in the P3MT film, |Δχ(3)| = |Δχ(3)1111(-ω2;ω2,-ω1,ω1)-Δ(3)1122(-ω2;ω2,-ω1, ω)|= 3.9×10-11esu was determined for ħω1= 1.97 eV and ħω2=1.88 eV.