Efficient generation of coherent THz phonons with a strong change in frequency excited by femtosecond laser plasma formed in a bulk of quartz

摘要

We observed a strong change in the frequency of coherent THz phonons from 1.4 to 4.6 THz under tight focusing (NA～0.4) of intense femtosecond laser radiation (～10 ~(13) W/cm 2) ignited the plasma within a bulk of quartz. Strong frequency shifts are caused by local heating of a microvolume (4×4×60 μm ~3) up to the temperature close to the α-β phase transition (846 K) of quartz. The effective target heating and coherent phonon excitation are provided via a laser-induced plasma.