Fig. 4: Calculations of pumped FSRS spectra in LiNbO3.
a, Equilibrium and pumped FSRS spectra for τ = 0.05 ps. The calculations were produced using a time-domain model for the FSRS process that is detailed in Supplementary Section 8. b, Group velocity of the FSRS probe projected onto the spacetime maps of QIR and QP from Fig. 1d. Over the course of the 50 µm sample depth, the probe velocity (vprobe) is approximately matched with the phase velocity of the soft-mode polariton. Here, the effective velocity of the probe was calculated given the group refractive index of LiNbO3 at 400 nm as well as the angle between the mid-infrared pump and white-light continuum pulse. c, Black, the dynamic Raman tensor used to produce the pumped calculations displayed in a. Red, the transient reduction of the Raman tensor seen in the rest frame of the probe after accounting for the effects of velocity mismatch throughout the 50 µm crystal thickness. The component that oscillates at 16 THz imparts sidebands to the frequencies of the equilibrium modes, giving rise to the blue-highlighted peaks in a.
