We demonstrate a new fast-scan ultrafast coherent reflectivity technique that tracks the amplitude and phase of excitons in GaAs heterostructures at densities down to 4 x 106 cm-2. Observed growth in the exciton coherence over the first 1.5 ps is direct evidence for the presence of interfering polariton modes. Polariton theory provides a good account of the data as the number of quantum wells is increased. Polariton motional narrowing of spectral lines from multiple quantum wells is demonstrated both experimentally and theoretically, annealing out the inhomogeneous broadening of the exciton energies.
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机译:我们展示了一种新的快速扫描超快相干反射率技术,该技术可在密度低至4 x 106 cm-2的情况下跟踪GaAs异质结构中激子的振幅和相位。在最初的1.5 ps内观察到的激子相干性增长是存在干扰极化子模式的直接证据。随着量子阱数量的增加,极化子理论很好地说明了数据。从实验和理论上都证明了来自多个量子阱的谱线的极化子运动变窄,可以消除激子能量的非均匀展宽。
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