Li Liang, He Wei, Liang Shiqi, Lan Pengfei, Lu Peixiang
Huazhong University of Science and Technology, Wuhan National Laboratory for Optoelectronics and School of Physics, Wuhan 430074, China.
Wuhan Institute of Technology, Hubei Key Laboratory of Optical Information and Pattern Recognition, Wuhan 430205, China.
Phys Rev Lett. 2025 Jun 6;134(22):223801. doi: 10.1103/PhysRevLett.134.223801.
We have investigated the transient properties of a ZnO crystal under a pump pulse (pumped crystal) using a pump-probe methodology. By monitoring the second harmonic of the weak probe pulse generated from the pumped crystal, we observe that the angular distribution of the second-harmonic yield becomes asymmetric compared to that without the pump. Importantly, the asymmetry of the second-harmonic generation (SHG) appears to be retarded by nearly 25 fs relative to the pump pulse, and its scaling shows a highly nonlinear dependence on the pump intensity. In addition, by using a two-color pump pulse, we further demonstrate that the asymmetry of SHG is controllable by adjusting the electric field of the two-color pulse. These phenomena can be attributed to the strong-field-induced electric-field-dependent Stark effect. Unlike the conventional intensity-dependent Stark effect, where only energy levels of the pumped target move, electric-field-dependent Stark effect indicates that the excitation induced by the pump pulse can distort the orbital and plays a vital role on the transient property of the pumped crystal. Our work suggests a new freedom for rationally designing the transient property of crystals by controlling the electric field of the pump pulse, which paves the way for realizing petahertz high-speed signal processing.
我们使用泵浦-探测方法研究了ZnO晶体在泵浦脉冲作用下（被泵浦的晶体）的瞬态特性。通过监测从被泵浦晶体产生的弱探测脉冲的二次谐波，我们观察到与无泵浦时相比，二次谐波产额的角分布变得不对称。重要的是，二次谐波产生（SHG）的不对称性相对于泵浦脉冲似乎延迟了近25飞秒，并且其标度显示出对泵浦强度的高度非线性依赖性。此外，通过使用双色泵浦脉冲，我们进一步证明了SHG的不对称性可通过调整双色脉冲的电场来控制。这些现象可归因于强场诱导的电场依赖型斯塔克效应。与传统的强度依赖型斯塔克效应不同，在传统效应中只有被泵浦靶的能级移动，而电场依赖型斯塔克效应表明泵浦脉冲诱导的激发会使轨道发生畸变，并在被泵浦晶体的瞬态特性中起关键作用。我们的工作为通过控制泵浦脉冲的电场合理设计晶体的瞬态特性提供了新的自由度，这为实现太赫兹高速信号处理铺平了道路。
