共查询到20条相似文献,搜索用时 140 毫秒
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《物理学报》2017,(4)
采用时间分辨圆偏振光抽运-探测光谱,测量了(110)晶向生长的近似对称和完全非对称掺杂GaAs/AlGaAs量子阱中的电子自旋弛豫,发现两种量子阱材料中的电子自旋弛豫时间随载流子浓度的增大均呈现出先增大后减小的趋势,且近似对称掺杂GaAs量子阱中的电子自旋弛豫时间明显大于完全非对称掺杂量子阱.分析表明,在(110)晶向生长的GaAs量子阱中并非只有通常认为的Bir-Aronov-Pikus(BAP)机理起作用,在低载流子浓度区域,两种量子阱中D′yakonov-Perel′(DP)机理起主导作用,高载流子浓度区域BAP机理和DP机理都起作用,完全非对称掺杂的量子阱中DP机理强于近似对称掺杂量子阱. 相似文献
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使用飞秒时间分辨抽运-探测透射光谱技术,实验研究了GaAs体材料中光激发载流子的超快弛豫动力学的波长依赖.在相同的光激发载流子浓度和抽运/探测比时,发现760 nm和780 nm两中心波长处的瞬态透射变化延迟扫描信号出现负的和振荡的信号.与模拟计算结果对比,判定该实验瞬态信号是错误的.分析探测器输出波形,发现是由于反相波形导致的,而引起反相波形的原因在于样品中存在长寿命的吸收过程.指出通过提高探测器上的抽运/探测比能够矫正反相波形,从而获得正确的瞬态透射变化动力学.提高探测器上的抽运/探测比与目前的应尽量减小抽运光对探测器的散射贡献的观点是对立的.文章的研究结果对应用抽运-探测时间分辨光谱技术正确地测量超快瞬态动力学过程具有重要的参考价值.
关键词:
时间分辨抽运-探测透射光谱
饱和吸收
吸收增强
GaAs体材料 相似文献
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利用飞秒激光脉冲在长度为10cm,包层具有大空气比的双折射微结构光纤中通过高阶模相位 匹配的四波混频获得了波长可调谐的反斯托克斯波.实验中脉冲宽度为35fs,中心波长820nm ,单脉冲能量4nJ的飞秒激光脉冲耦合到长轴直径为5μm,短轴为46μm的双折射微结构光 纤中.在高阶模传输情况下,通过调制耦合光的偏振方向,获得了具有不同中心波长的反斯 托克斯波.通过对比分析,讨论了输入光的偏振态对双折射微结构光纤中高阶模式下四波混 频效应的影响情况.理论计算分析很好的解释了实验结果.
关键词:
微结构光纤
飞秒脉冲激光
四波混频 相似文献
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G. Cassabois S. Meccherini Ph. Roussignol F. Bogani M. Gurioli M. Colocci R. Planel V. Thierry-Mieg 《Physica E: Low-dimensional Systems and Nanostructures》1998,2(1-4)
The intermediate dimensionality regime is studied on a set of shallow GaAs/Ga
Al
As single quantum wells. Such heterostructures exhibit 2D strong excitonic electroabsorption together with near 3D fast transport properties. We report dephasing time measurements
of the heavy-hole exciton and we show that the acoustic phonon contribution decreases with
to a value in good agreement with theoretical predictions for GaAs bulk. 相似文献
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加偏置电场的抛物量子阱中的电光效应 总被引:2,自引:2,他引:0
本文利用密度矩阵方法得到了加偏置电场的抛物量子阱中电光效应的解析表达式,并以典型的GaAs抛物量子阱为例进行了数值计算研究结果表明,电光效应随偏置电场和抛物势频率的增大而增强,同时也表明GaAs量子阱中的电光效应比体GaAs中的要强一个数量级以上。 相似文献
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Carrier recombination and electron spin relaxation dynamics in asymmetric n-doped (110) GaAs/AlGaAs quantum wells are investigated with time-resolved pump-probe spectroscopy. The experiment results reveal that the measured carrier recombination time depends strongly on the polarization of pump pulse. With the same pump photon flux densities, the recombination time of spin-polarized carriers is always longer than that of the spin-balanced carriers except at low pump photon flux densities, this anomaly originates from the polarization-sensitive nonlinear absorption effect. Differing from the traditional views, in the low carrier density regime, the D'yakonov–Perel' (DP) mechanism can be more important than the Bir–Aronov–Pikus (BAP) mechanism, since the DP mechanism takes effect, the spin relaxation time in (110) GaAs QWs is shortened obviously via asymmetric doping. 相似文献
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Bel'kov VV Olbrich P Tarasenko SA Schuh D Wegscheider W Korn T Schüller C Weiss D Prettl W Ganichev SD 《Physical review letters》2008,100(17):176806
Symmetry and spin dephasing in (110)-grown GaAs quantum wells (QWs) are investigated applying magnetic field induced photogalvanic effect and time-resolved Kerr rotation. We show that magnetic field induced photogalvanic effect provides a tool to probe the symmetry of (110)-grown quantum wells. The photocurrent is only observed for asymmetric structures but vanishes for symmetric QWs. Applying Kerr rotation we prove that in the latter case the spin relaxation time is maximal; therefore, these structures set the upper limit of spin dephasing in GaAs QWs. We also demonstrate that structure inversion asymmetry can be controllably tuned to zero by variation of delta-doping layer positions. 相似文献
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JETP Letters - Electron spin dephasing anisotropy is studied in GaAs/AlGaAs coupled quantum wells by means of a timeresolved Kerr rotation technique. It is found that the spin dephasing rate is... 相似文献
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K. Unterrainer R. Kersting R. Bratschitsch G. Strasser J. N. Heyman K. D. Maranowski A. C. Gossard 《Physica E: Low-dimensional Systems and Nanostructures》2000,7(3-4)
Optically excited plasma oscillations in n-doped GaAs epilayers emit intense THz pulses. Using a THz-pump and THz-probe technique we observe the response of the intersubband polarization in semiconductor quantum structures. THz Cross-correlation measurements of modulation doped semiconductor quantum structures allow to determine the absorption, the dispersion, and the dephasing times of the quantized electrons. 相似文献
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Results of continuous excitation, time-delayed and time-resolved cathodoluminescence experiments on undoped and Be-doped GaAs multiple quantum wells of thickness 5–11 nm are reported for temperatures 5–300 K and excitation intensities 1–103 W/cm2. Comparison is made with similar investigations of bulk epitaxial GaAs layers. Increasing structural localisation of the carriers is identified to lead to a qualitative change of the type of recombination. Increasingly faster radiative excitonic recombination leads to a bypass of impurity and trap capture processes in undoped as well as in doped material, at low temperatures as well as at room temperature. Despite the exponential character of excitonic decay, the luminescence transients are found to be very complex due to an interplay of intersubband scattering and recombination processes and time-dependent carrier temperature. Transients are analysed in detail, excitonic lifetimes and intersubband scattering times are derived. It is argued that both the lifetime reduction in quantum wells and the novel process of recombination heating lead to a strongly increased quasiequilibrium temperature of excited carriers in the wells as compared to bulk material. Injection of carriers from 18 nm GaAlAs barriers to GaAs wells is found to occur in less than 10-12 s without loss. 相似文献
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Photoinduced high-density phase of exciton-polariton masses excited at a two-dimensional stacking fault interface in BiI 3 has been studied by observing the degenerate four-wave-mixing (DFWM) signals. It was found that the increase in the dephasing rate due to exciton-exciton collisions is suppressed above a threshold excitation density. Above such density, a coherently propagating component of the exciton masses was detected on the space-resolved DFWM signals obtained by applying the spatially isolated two-spot excitation with a picosecond laser. In this scheme the off-diagonal element of the density matrix of the excitons at the one exciting laser spot propagates to the other, bringing about nonlinear polarization to yield the DFWM light. Time evolution of the space-resolved DFWM signals reveals evidently the macroscopic expansion of the exciton-polariton masses in a photoinduced condensed phase. Energy splitting of the DFWM spectra obtained with a narrow-band laser shows a repulsive interaction between the excitons. 相似文献
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We have addressed the dependence of quasi-two-dimensional electron spin dephasing time on the electron gas density in a 17-nm GaAs quantum well using the time-resolved magneto-optical Kerr effect. A superlinear increase in the electron dephasing time with decreasing electron density has been found. The degree of electron spin relaxation anisotropy has been measured and the dependence of spin-orbit splitting on electron gas density has been determined. 相似文献