Lin Haw-Wei, Mead Griffin, Blake Geoffrey A
Division of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena, California 91125, USA.
Division of Chemistry and Chemical Engineering and Division of Geology and Planetary Sciences, California Institute of Technology, Pasadena, California 91125, USA.
Phys Rev Lett. 2022 Nov 11;129(20):207401. doi: 10.1103/PhysRevLett.129.207401.
Two-dimensional terahertz-terahertz-Raman spectroscopy can provide insight into the anharmonicities of low-energy phonon modes-knowledge of which can help develop strategies for coherent control of material properties. Measurements on LiNbO_{3} reveal THz and Raman nonlinear transitions between the E(TO_{1}) and E(TO_{3}) phonon polaritons. Distinct coherence pathways are observed with different THz polarizations. The observed pathways suggest that the origin of the third-order nonlinear responses is due to mechanical anharmonicities, as opposed to electronic anharmonicities. Further, we confirm that the E(TO_{1}) and E(TO_{3}) phonon polaritons are excited through resonant one-photon THz excitation.
二维太赫兹-太赫兹-拉曼光谱能够深入了解低能声子模式的非谐性，掌握这方面的知识有助于制定对材料特性进行相干控制的策略。对铌酸锂的测量揭示了E(TO₁)和E(TO₃)声子极化激元之间的太赫兹和拉曼非线性跃迁。在不同的太赫兹偏振下观察到了不同的相干路径。观察到的路径表明，三阶非线性响应的起源是机械非谐性，而非电子非谐性。此外，我们证实E(TO₁)和E(TO₃)声子极化激元是通过共振单光子太赫兹激发而被激发的。
