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主要从实验和理论两个方面,探讨了强受限尺寸区域内不同尺寸对CdSe量子点线性和非线性光学性质的影响.用吸收光谱研究了量子点尺寸与吸收峰之间的关系,用皮秒Z扫描技术研究了共振和非共振情况下(激发光波长分别为532和1064nm),尺寸与三阶非线性极化率之间的关系.基于电子能量状态理论和局域场增强理论对量子点进行分析,得到了CdSe不同尺寸的三阶非线性效应,研究了尺寸对量子点非线性光学性质的影响.结果表明,由激发态粒子数布局改变和纳米颗粒增大引起的非线性共振增强效应相当,二者共同作用使得三阶极化率增强20倍左右,且用532nm的共振频率激发4.3nm CdSe量子点时,χ(3)具有最大值2.0×10-11esu.
关键词:
CdSe量子点
三阶非线性
Z扫描')" href="#">Z扫描
量子限域效应 相似文献
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周书华 周静 孟秋英 S.Ajimura H.Akikawa D.E.Alburger A.Banu R.E.Chrien G.B.Franklin J.Franz O.Hashimoto T.Hayakawa H.Hotchi K.Imai< 《中国物理 C》2005,29(7):627-631
在用HYPERBALL进行的16ΛO的γ射线谱学测量中, 观察到由16ΛO的6.6 MeV 1-2 激发态跃迁到基态自旋翻转二重态( 1-1和0-)之间的两条γ射线. 由这两条γ射线的能量差得到基态二重态之间的能量间隔为26.4 ± 1.6(stat) ± 0.5(syst) keV, 并由此推导出ΛN之间的张量相互作用强度T=0.03MeV.实验还测定了16ΛO的激发态的激发能为6561.7 ± 1.1(stat) ± 1.7(syst) keV. 相似文献
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单分子荧光过程的Monte-Carlo模拟 总被引:1,自引:0,他引:1
从单分子发光过程中电子在激发态上的停留时间t服从P(t)=γe-γt分布出发,对单分子荧光过程进行M-C(Monte-Carlo)随机试验,得到了单分子的激发态相邻两次发光的时间间隔的统计结果以及单分子荧光强度的自相关函数,并对其进行了详细地讨论,这些结果与目前文献报道的实验结果相一致. 相似文献
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The energy differences for 19 pairs of γ rays are measured with a γ spectrometer. The first γ transition in each pair is excited in decay of 191Pt, and the second transition, accompanying the decay of 182Ta or 192Tr is a third-order nuclear spectroscopic normal. The energies of nine 191Ir levels and 36 γ-ray photons accompanying decay of 191Pt, were determined with high accuracy on the basis of these data. 相似文献
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The prospects for the enhancement of the third-order optical nonlinearity in the mesoscopic semiconductor structures: quantum wells, wires, and boxes are analyzed. It is shown, that if the structures are designed in such a way that the ground state and the excited states wavefunctions are spatially separated, then the electrostatic Coulomb interactions will result in the enhancement of the optical nonlinearity. The enhancement factor has been analyzed for the structures of different shapes and material compositions. It was found that the possible enhancement factor ranges from 2 for quantum wells to 10 for quantum wires and boxes. 相似文献
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T. Johr W. Werncke L. Dähne M. Pfeiffer A. Lau 《Applied physics. B, Lasers and optics》1996,63(6):641-647
The dispersion of the third-order susceptibility of the cyanine dye bis-(dimethylamino)-heptamethinium chloride was measured by Coherent Anti-Stokes Raman Scattering (CARS) over a wide wavelength range from 530 to 830 nm. Large negative values of the real part of the second-order hyperpolarizability are observed. The data are analyzed with the help of theoretical calculations based on a perturbative approach for the nonlinearities. The dispersion behavior of the third-order susceptibility is governed by the resonant enhancement due to vibrational transitions of the first excited electronic state and, to lesser extent, by an electronic two-photon resonance around 600 nm. 相似文献
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The dynamics of hydrogen atom in the presence of a strong radiation field of the titanium-sapphire laser is studied for the Keldysh parameters γ ≥ 1 and γ ≤ 1. It is demonstrated that the ionization is supplemented with the effective population of the excited states with the principal quantum numbers n = 5–10 in the entire range of variation in the Keldysh parameter. The population of the excited Rydberg states can be interpreted as a consequence of the multiphoton resonance involving the initial 1s state and a group of excited states in the vicinity of the continuum boundary with the simultaneous repopulation of these states by Λ-type Raman transitions under the action of the laser field. The resulting coherent Rydberg packet appears to be stable with respect to ionization, so that the ionization of the atomic system in the presence of strong electromagnetic field is suppressed. Physical reasons for the stabilization are discussed. An interpretation of the effective population of the Rydberg states in the recent experiments on the ionization of atomic helium by the titanium-sapphire laser is proposed. 相似文献
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Nonlinear absorption dynamics of oxidized cytochrome c in water solution was investigated at 532 nm with Z-scan and pump–probe techniques. The optical characterization of this compound is very important owing to its similarity with hematoporphyrin-based drugs commonly used in photodynamic therapy for cancer treatment. We observed a saturable absorption process related to the excited singlet population, followed by a fast decay to the ground state. The optical excitation and subsequent relaxation were interpreted with a three-energy-level diagram, allowing the first singlet excited-state absorption cross section and lifetime determination. PACS 42.65.Sf; 78.66.Qn; 42.62.Be 相似文献
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The femtosecond time-resolved difference absorption spectra of all-trans-βApo-8′-carotenal have been recorded and analyzed by the singular-value decomposition (SVD) method followed by global fitting using a sequential model for the excited-state energy relaxation. With this model, we have obtained the excited-state absorption spectra and the lifetimes of the corresponding excited states both in nonpolar solvent n-hexane and polar solvent methanol. Three excited states, namely S3(170fs), S2(2.32ps) and S1(26ps) in n-hexane, and two excited states S2 (190fs) and S1(9.4ps) in methanol have been observed. The excited-state absorption spectra of all-trans-β-Apo-8′-carotenal in methanol display a red shift and broadeness, while the lifetime of S1 state becomes shorter. It is proposed that these effects are related to the presence of a carbonyl functional group that leads to the solvent effect on the excited-state energy level. At the same time, it is shown that the SVD method is a useful tool in resolving the time-resolved absorption spectra. 相似文献
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Excited-state dynamics of magnesium phthalocyanine thin film 总被引:1,自引:0,他引:1
Jun Mi Lijun Guo Ye Liu Weimin Liu Guanjun You Shixiong Qian 《Physics letters. A》2003,310(5-6):486-492
Ultrafast excitation relaxation dynamics of magnesium phthalocyanine (MgPc) thin film were investigated by femtosecond pump-probe spectroscopy. The excited state dynamics of MgPc's Q-band were found to be strongly dependent on the probe wavelength. Ultrafast exciton–exciton annihilation with a t−1/2 time dependence of the excited-state population was observed. 相似文献
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1IntroductionFormakingthealopticalswitchingpracticality,theopticalnonlinearityofmaterialhastoreachacertainorderofmagnitude[1... 相似文献