Gao Y, Zeng X Y, Wang X B, Shi Y G, Cheng L, Qi J
Opt Lett. 2024 Jul 15;49(14):3862-3865. doi: 10.1364/OL.525200.
The substantial nonlinear optical response observed in numerous topological materials renders them well-suited for optic and photonic applications, underscoring the critical need to devise effective strategies for manipulating their nonlinearity to enhance their versatility across different applications. In this Letter, we focus on the second-harmonic generation (SHG) response of the topological material PtBi under intense terahertz (THz) pulses and unveil the transient nonlinearity manipulated by a THz electric field. Our findings demonstrate that upon excitation of an intense THz pulse, there emerges a substantial enhancement in the SHG signal of PtBi, which is predominantly attributed to the linear term involving the THz field, i.e., χχE. We also clearly observe the transient change in the nonlinear coefficients, which could arise from the excitation of the bands with linear dispersion via the intense THz pulse. These findings bear significant implications for achieving ultrafast modulation of nonlinearity in topological materials, thereby opening avenues for advanced applications in this field.
在众多拓扑材料中观察到的显著非线性光学响应使其非常适合光学和光子应用，这突出表明迫切需要设计有效的策略来操纵它们的非线性，以增强其在不同应用中的通用性。在本信函中，我们聚焦于拓扑材料PtBi在强太赫兹（THz）脉冲下的二次谐波产生（SHG）响应，并揭示由太赫兹电场操纵的瞬态非线性。我们的研究结果表明，在强太赫兹脉冲激发后，PtBi的SHG信号出现显著增强，这主要归因于涉及太赫兹场的线性项，即χχE。我们还清晰地观察到非线性系数的瞬态变化，这可能是由强太赫兹脉冲激发具有线性色散的能带所致。这些发现对于实现拓扑材料中非线性的超快调制具有重要意义，从而为该领域的先进应用开辟了道路。
