[20a-C301-1~9] 3.5 Ultrashort-pulse and high-intensity lasers

9:15 AM - 9:30 AM JST(12:15 AM - 12:30 AM UTC)

[20a-C301-2] Mid-infrared anomalous propagation in water thin film probed by second harmonics

〇Takayuki Kurihara¹, Yangyang Hua¹, Tianqi Yang¹, Tomoya Mizuno¹, Yoshihisa Harada¹, Jiro Itatani¹ (1.ISSP, Univ. Tokyo)

Keywords:

Mid-infrared,Superluminal propagation effect,Water

The molecular vibration of water exhibits resonant absorption in the mid-infrared region. In this study, we resonantly excited the molecular vibrations of water by femtosecond mid-infrared pulses in the region around 3 um and observed the induced polarisation dynamics by the field-induced second harmonic generation of a 7 fs visible probe pulse. In the case of resonant pumping, the second harmonics waveform was observed to show onset several 10 fs earlier than the original mid infrared waveform, indicating the occurence of the so called 'superluminal propagation effect' due to the negative group refractive index.