Fig. 2: Nonlinearity-induced coupling into and “escaping” from the topological interface state. | Light: Science & Applications

Fig. 2: Nonlinearity-induced coupling into and “escaping” from the topological interface state.

From: Nontrivial coupling of light into a defect: the interplay of nonlinearity and topology

Fig. 2

The illustration on the left shows two-beam tilted excitations (green arrows) of the topological defect from opposite directions. The top panels are from the experiment, where (a1) shows the cross-section of the lattice, (a2) shows the output of a topological interface state under single-beam (straight) excitation, and (b1) and (b2) show the outputs of two tilted in-phase beams (\(k_{x} = \pm 1.4 \pi/a\)) under linear and nonlinear excitation conditions. The bottom panel (b3) is from the simulation, showing a side view of the beam dynamics (up to a length of 40 mm) under nonlinear excitation. The right panels (c1–c3) have the same layout as (b1–b3) except that the defect is excited with two tilted out-of-phase beams. The white dashed-dotted line marks the position of the nontrivial interface defect channel in the SSH lattice in all figures

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