Ultrafast dynamics of optical phonons in α-quartz launched by THz wave and femtosecond laser combined excitation source

We use the terahertz (THz) wave generated from the 1550 nm femtosecond laser excited DAST crystal and an 800 nm femtosecond laser to jointly focus on the α-quartz crystal, and prompt it to produce ultrafast coherent phonon dynamic effect. The experimental phenomena were detected by means of THz Time-Domain Spectroscopy. We found that when the two excitation beams have different relative time delays, the oscillation frequencies of the phonon generated by the quartz crystal shift. It is of great importance for us to study phonon dynamics of quartz crystal and other materials.