Figure 4 shows G-phonon dynamics with pump fluence 2.1 mJ/cm2 and 0.15 mJ/cm2 respectively. The phonon dynamics are similar for these two pump powers. Maximum phonon temperature decreases with lower pump fluence as expected. The generation of G phonons is slower with low pump fluence (τgrowth = 210 fs) than for the high pump fluence (τgrowth = 100 fs).