Observation of Edge Solitons in Topological Trimer Arrays

Area of Science:

• Nonlinear optics
• Condensed matter physics
• Photonic systems

Background:

• Light localization and soliton formation are key phenomena in nonlinear optics.
• Topological phases in photonic systems offer unique properties for light manipulation.
• Waveguide arrays provide a platform for studying light propagation dynamics.

Purpose of the Study:

• To experimentally investigate nonlinear light localization and edge soliton formation in fs-laser written trimer waveguide arrays.
• To explore the transition between nontopological and topological phases and its effect on soliton behavior.
• To demonstrate the coexistence and selective excitation of different types of topological edge solitons.

Main Methods:

• Fabrication of trimer waveguide arrays using femtosecond laser writing.
• Experimental observation of nonlinear light propagation and soliton formation.
• Control of topological phase transitions by adjusting inter-trimer spacing.

Main Results:

• Edge solitons were observed in both nontopological and topological regimes.
• In nontopological phases, edge solitons required a high power threshold.
• In topological phases, edge solitons bifurcated from linear states and were observed over a broad power range.
• Partial delocalization occurred when nonlinearity drove propagation constants into allowed bands, coupling with bulk modes.
• Two types of topological edge solitons with distinct structures were selectively excited in different topological gaps.
• First experimental evidence of topological soliton formation in a system with multiple topological gaps was presented.

Conclusions:

• The study experimentally confirms the distinct formation mechanisms of edge solitons in nontopological and topological regimes.
• It demonstrates the coexistence and controllable excitation of diverse topological edge solitons.
• This work pioneers the observation of topological solitons in nonlinear systems with multiple topological gaps, opening avenues for novel photonic applications.