【摘要】 用双光束诱导半导体GaAs的激子相干态, 记录液氮温度样品的光电导信号随双脉冲之间延时的变化。实验与理论分析结果表明: 对于均匀增宽的二能级体系, 这种测量方法可以直接反映相干态的自由感应衰减。求解均匀增宽二能级体系的密度矩阵方程, 拟合实验结果得到载流子相干态的退相时间T2 = 115 f更多还原

【Abstract】 Coherent properties for excitons and for free carriers in intrinsic bulk GaAs are studied with femtosecond free induction decay (FID). The GaAs at 77 K is excited at its excitonic energy with dual fs pulses from a Ti∶Sapphire laser and the FID is recorded through photocurrent detection. The dephasing rates are determined by comparing the FID with theoretical results for density matrix in homogeneouse brodening two level system.更多还原