Figure 2: TR and TSHG traces for the 10 nm thick Bi2Se3 film.

Upper panel shows TR and TSHG traces for the 10 nm Bi2Se3 film simultaneously measured with 250 fs step-size in the Sin−Ppump−Sout polarization geometry at different pump/probe powers as indicated by the corresponding colours. The TSHG section also indicates the frequency and damping coefficient of the oscillatory part of the TSHG trace. Lower panel shows the corresponding longer delay-time range TSHG trace measured with 1 ps step-size at 640/580 mW pump/probe powers. The normalized TSHGRA patterns measured at the fixed pump-to-probe delay times as indicated by arrows are shown in the corresponding insets. The red curves in both panels present the best fit to the data.