Figure 3: Dynamic control of the phonon modes of a Swiss-cross with temporal coherent control.

For a designed nanostructure, temporal coherent control can change the phonon modes on demand. (a) In the 120 × 90 nm Swiss-cross structure where both modes are excited (i) pump and control pulses separated by an appropriate time delay can selectively excite the higher frequency symmetric mode (ii) or the lower frequency antisymmetric mode (iii). Without coherent control, both modes are excited (i). The control pulse delay is the delay between the first pump pulse and the second pump pulse. In the transient transmission spectra (b), the two sharp dips are the pump and control pulses that are temporally separated by the control pulse delay. The phonon spectra i, ii and iii are produced with pump-control pulse delays of 5, 46 and 100 ps. The amplitude as a function of frequency and pump-control pulse delay is shown in c, with specific traces corresponding to the symmetric (green dots) and antisymmetric modes (red dots) are shown in d. The parameters for the calculation (solid line) are derived from the fit of the 5-ps control pulse delay pump experiment (grey curve i in a) with the fit function in Supplementary Note 1.