通过相干太赫兹驱动非对称晶格位移实现β-巴硅酸盐的二次谐波生成的全光控制
All-optical control of second-harmonic generation in $β$-BaB$_2$O$_4$ via coherent, terahertz-driven acentric lattice displacement
AI总结：
本研究通过太赫兹脉冲诱导晶格变形，实现对β-巴硅酸盐二次谐波生成的高效调制，揭示了共振选择性晶格激发机制。
摘要：
动态控制固体的非线性光学性质--通过光本身--对于未来超快光子技术至关重要。此前，调节包括二次谐波生成（SHG）在内的非线性过程的方法主要依赖于非共振的光物质相互作用或在纳米尺度材料中通过光产生热电子。然而，这些方法通常受到相互作用长度有限的限制，并且在平衡条件下初始频率转换相对较弱。在这里，通过强太赫兹（THz）脉冲诱导的瞬时晶格变形，实现了对β-钡硼酸盐（beta-BaB2O4）中高效相匹配SHG的约30%调制。该效应源于对折射率椭球的修改以及相应的非线性相匹配条件的改变，而不是通过THz介导的chi^(3)过程直接调制非线性电荷率。这种共振选择性晶格激发机制指向了新的THz控制方案，用于调节材料中的非线性光学响应。
英文摘要：
Dynamical control of the nonlinear optical properties of solids -- with light itself -- will be essential for future ultrafast photonic technologies. Previously, methods to modulate nonlinear processes including second-harmonic generation (SHG) have relied primarily on non-resonant light-matter interaction or photo-generation of hot electrons in nanoscale materials. However, these approaches are typically constrained by limited interaction lengths and the initial frequency conversion is relatively weak under equilibrium conditions. Here, an approximately 30\% modulation of efficient phase-matched SHG in bulk beta-barium borate (beta-BaB2O4) is achieved through transient lattice deformation by intense terahertz (THz) pulses that are tuned to resonance with an infrared-active phonon mode. The effect originates from modification of the index of refraction ellipsiod and the corresponding nonlinear phase-matching conditions, rather than from direct modulation of the nonlinear susceptibility through THz-mediated chi^(3) processes. This mechanism, of resonant selective lattice excitation, points toward novel THz-control schemes to tune the nonlinear optical response in materials.
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