Ginsberg Jared S, Jadidi M Mehdi, Zhang Jin, Chen Cecilia Y, Tancogne-Dejean Nicolas, Chae Sang Hoon, Patwardhan Gauri N, Xian Lede, Watanabe Kenji, Taniguchi Takashi, Hone James, Rubio Angel, Gaeta Alexander L
Department of Applied Physics and Applied Mathematics, Columbia University, New York, New York, NY, 10027, USA.
Max Planck Institute for Structure and Dynamics of Matter and Center for Free-Electron Laser Science, Hamburg, 22761, Germany.
Nat Commun. 2023 Nov 24;14(1):7685. doi: 10.1038/s41467-023-43501-x.
Polar crystals can be driven into collective oscillations by optical fields tuned to precise resonance frequencies. As the amplitude of the excited phonon modes increases, novel processes scaling non-linearly with the applied fields begin to contribute to the dynamics of the atomic system. Here we show two such optical nonlinearities that are induced and enhanced by the strong phonon resonance in the van der Waals crystal hexagonal boron nitride (hBN). We predict and observe large sub-picosecond duration signals due to four-wave mixing (FWM) during resonant excitation. The resulting FWM signal allows for time-resolved observation of the crystal motion. In addition, we observe enhancements of third-harmonic generation with resonant pumping at the hBN transverse optical phonon. Phonon-induced nonlinear enhancements are also predicted to yield large increases in high-harmonic efficiencies beyond the third.
通过将光场调谐到精确的共振频率,可以驱动极性晶体进入集体振荡状态。随着激发声子模式振幅的增加,与所施加场呈非线性比例关系的新过程开始对原子系统的动力学产生影响。在此,我们展示了由范德华晶体六方氮化硼(hBN)中的强声子共振所诱导和增强的两种此类光学非线性效应。我们预测并观察到在共振激发期间由于四波混频(FWM)产生的持续时间为亚皮秒级的大信号。由此产生的FWM信号使得能够对晶体运动进行时间分辨观测。此外,我们观察到在hBN横向光学声子处进行共振泵浦时三次谐波产生的增强。声子诱导的非线性增强效应预计还会使高于三次谐波的高谐波效率大幅提高。