Topologically enhanced harmonic generation in a nonlinear transmission line metamaterial

• Published in: Nature communications Vol. 10; no. 1; p. 1102
• Main Authors: Wang, You, Lang, Li-Jun, Lee, Ching Hua, Zhang, Baile, Chong, Y. D.
• Format: Journal Article
• Language: English
• Published: London Nature Publishing Group UK 07.03.2019; Nature Publishing Group; Nature Portfolio
• Subjects: 639/624/400/3923; 639/766/1130; 639/766/119/2792; Circuits; Eigenvalues; Electronic circuits; Frequency generators; Handedness; Harmonic generations; Humanities and Social Sciences; Metamaterials; multidisciplinary; Nonlinear systems; Nonlinearity; Physics; Printed circuit boards; Science; Science (multidisciplinary); Shock waves; Transmission lines
• ISSN: 2041-1723; 2041-1723
• DOI: 10.1038/s41467-019-08966-9

Nonlinear transmission lines (NLTLs) are nonlinear electronic circuits used for parametric amplification and pulse generation, and it is known that left-handed NLTLs support enhanced harmonic generation while suppressing shock wave formation. We show experimentally that in a left-handed NLTL analogue of the Su-Schrieffer-Heeger (SSH) lattice, harmonic generation is greatly increased by the presence of a topological edge state. Previous studies of nonlinear SSH circuits focused on solitonic behaviours at the fundamental harmonic. Here, we show that a topological edge mode at the first harmonic can produce strong propagating higher-harmonic signals, acting as a nonlocal cross-phase nonlinearity. We find maximum third-harmonic signal intensities five times that of a comparable conventional left-handed NLTL, and a 250-fold intensity contrast between topologically nontrivial and trivial configurations. This work advances the fundamental understanding of nonlinear topological states, and may have applications for compact electronic frequency generators. Higher harmonic generation can be enhanced in left-handed nonlinear transmission lines. Here Wang et al. show that the presence of a topological edge state in a circuit analogue of the Su-Schrieffer-Heeger model can increase this enhancement even further.