Experimental and Theoretical Investigation of Ultrafast Coherent Phenomena in Semiconductors

在这个项目中，我们将研究半导体非平衡多体效应在理论和实验合作中的作用。我们将尝试演示首次观测到的拉比振荡(RO)和强飞秒脉冲在半导体中的共振传播。拉比振荡和共振脉冲传播，甚至自感透明(SIT)，已经在原子系统中看到，但还没有在半导体中被观察到。我们的多体计算预测，当使用比退相T2倍更短的飞秒激光脉冲时，半导体中可能会出现RO。此外，这些计算还预测，与原子系统相比，半导体中的强脉冲传播和自感透明将发生重大修改。我们的目标之一是对调谐到GaAsAlGaAs多量子阱中激发共振的脉冲进行互相关实验样本来验证这些预测，并展示半导体和原子系统中的SIT之间的差异。我们计划在明确的条件下，定量地研究量子阱和块体材料中的载流子弛豫和退相。从理论上讲，我们最近在块状半导体中发现了一种适合于非平衡载流子的新的无阻尼声等离子体模分配。根据我们的计算，相关的超快载流子-载流子散射和退相应该与本征的显著不同，N和P掺杂材料，因为低动量态的电子是声等离激元衰减的主要原因。将在半导体的增益区中执行光谱烧孔，偏振退相时间将使用烧孔的宽度来测量。这些测量结果将与我们的计算结果进行比较，应提供有关载波弛豫和去相速率的重要信息。

In this project we will investigate the semiconductor nonequilibrium many-body effects in a theory- experiment collaborative effort. We will attempt to demonstrate the first observation of Rabi oscillations (RO) and resonant propagation of strong femtosecond pulses in a semiconductor. Rabi oscillations and resonant pulse propagation, even self-induced transparency (SIT), have been seen in atomic systems, but have not yet been observed in semiconductors. Our many-body calculations have predicted that RO may be seen in semiconductors when femetosecond laser pulses shorter than the dephasing T2 times are employed. Also, these calculations predict significant modifications of strong pulse propagation and self-induced transparency in semiconductors, as compared to atomic systems. One of our goals is to perform cross- correlation experiments for pulses tuned to the excition resonance in a GaAs-AlGaAs multiple quantum well sample to verify these predictions and demonstrate the differences between SIT in semiconductors versus atomic systems. We plan to quantitatively investigate carrier relaxation and dephasing in quantum wells as well as in bulk materials under well- defined conditions. Theoretically, we recently found a new undamped acoustic plasmon mode in bulk semiconductors for suitable nonequilibrium carrier distributions. According to our calculations, the related ultrafast carrier-carrier scattering and dephasing should be significantly different for intrinsic, n- and p- doped materials, since the electrons in low momentum states are primarily responsible for the acoustic plasmon damping. Spectral hole burning in the gain region of semiconductors will be performed, and polarization dephasing times will be measured using the width of the burned holes. These measurements, which will be compared with our calculations, should yield important information on carrier relaxation and dephasing rates.