Extended Data Fig. 3: Saturation of phonon amplitude at high pump fluence.
From: Terahertz phonon engineering with van der Waals heterostructures
a, The pump-induced FLG absorption signal of device 3 at \(\Delta t=0\) (similar to that shown in Extended Data Fig. 1d) at pump fluence of 450 μJ/cm2 and 1210 μJ/cm2 show a roughly linear increase of the FLG absorption as a function of pump fluence (weak saturation). b, The peak-to-peak amplitude of the first phonon pulse at Δt = 6.2 ps at pump fluence of 450 μJ/cm2 and 1210 μJ/cm2 show strong saturation at the high pump fluence. The sublinear dependence in a implies that not all pump power is absorbed by FLG, and the stronger sublinear dependence in b implies that not all absorbed power is converted to phonon amplitudes at high pump fluence.
