Strain engineering has been extended recently to the picosecond timescales, driving ultrafast metal–insulator phase transitions and the propagation of ultrasonic demagnetization fronts. However, the nonlinear lattice dynamics underpinning interfacial optoelectronic phase switching have not yet been addressed. Here we perform time-resolved all-optical pump-probe experiments to study ultrafast lattice dynamics initiated by impulsive light excitation tuned in resonance with a polar lattice vibration in LaAlO₃ single crystals, one of the most widely utilized substrates for oxide electronics. We show that ionic Raman scattering drives coherent rotations of the oxygen octahedra around a high-symmetry crystal axis. By means of DFT calculations we identify the underlying nonlinear phonon–phonon coupling channel. Resonant lattice excitation is also shown to generate longitudinal and transverse acoustic wave packets, enabled by anisotropic optically induced strain. Importantly, shear strain wave packets are found to be generated with high efficiency at the phonon resonance, opening exciting perspectives for ultrafast material control.

应变工程最近已扩展到皮秒级的时间尺度，从而驱动了金属-绝缘体的超快相变以及超声消磁前沿的传播。但是，尚未解决支撑界面光电相转换的非线性晶格动力学问题。在这里，我们进行时间分辨的全光学泵浦探针实验，以研究由LaAlO ₃的极性晶格振动共振调谐的脉冲光激发引发的超快晶格动力学。单晶，氧化物电子学中使用最广泛的衬底之一。我们表明离子拉曼散射驱动氧八面体围绕高对称晶体轴的相干旋转。通过DFT计算，我们确定了潜在的非线性声子-声子耦合通道。还显示了共振晶格激发产生各向异性的光学感应应变而产生的纵向和横向声波包。重要的是，发现在声子共振时会高效产生剪切应变波包，为超快材料控制开辟了令人兴奋的前景。