Fig. 2
From: Topological characterizations of an extended Su–Schrieffer–Heeger model
a The experimental setup for multifrequency Raman coupling. The incoming Raman beam passes the BEC, then passes two AOMs, and finally propagates back to the BEC. One AOM is modulated with a frequency f0, and the other one is modulated with the multifrequency signal \(f_0 + {\sum} f_n\). One AOM is operated in the positive first order. while the other is operated in the negative first order. So the two Raman beams on BEC differ in frequency by \({\sum} f_n\). b An illustration of the Raman processes driven by a pair of Raman beams
