Abstract We report an experimental study on the ultrafast dynamics of coherent longitudinal acoustic phonons (CLAPs) in GaAs single crystals with different orientations by using femtosecond pump–probe technique. Under an above-bandgap pumping at 400 nm, the CLAP wave is generated on the surface of a GaAs crystal with [100] orientation, and then it propagates into the crystal and is detected by the transient reflection of the probe beam at 800 nm. As the pumping intensity is increased, the amplitude and lifetime of generated CLAPs in GaAs crystals are increased and decreased respectively, while the phonons oscillation frequency remains a constant of 44 . 3 ± 0 . 2 GHz. Furthermore, the CLAPs frequency is varied in GaAs crystals with different orientations which is determined by the elastic anisotropy. In addition, from the initially opposite oscillation phase of [100] and [111] oriented GaAs, tensile or compressive lattice stresses can be easily determined. Our results can facilitate the understanding of ultrafast phonon dynamics in GaAs single crystals.

中文翻译：

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GaAs 中不同取向的单晶中千兆赫兹相干纵向声子

摘要 我们报告了使用飞秒泵浦探针技术对不同取向的 GaAs 单晶中相干纵向声子 (CLAP) 的超快动力学进行的实验研究。在 400 nm 的带隙以上泵浦下，在 [100] 取向的 GaAs 晶体表面产生 CLAP 波，然后它传播到晶体中，并被 800 nm 探测光束的瞬态反射检测到。随着泵浦强度的增加，GaAs 晶体中产生的 CLAPs 的振幅和寿命分别增加和减少，而声子振荡频率保持恒定为 44。3±0。2 GHz。此外，在由弹性各向异性决定的不同取向的 GaAs 晶体中，CLAPs 频率是变化的。此外，从 [100] 和 [111] 取向的 GaAs 最初相反的振荡相位，可以很容易地确定拉伸或压缩晶格应力。我们的结果有助于理解 GaAs 单晶中的超快声子动力学。