We study light propagation in waveguide arrays made in Kerr nonlinear media with a transverse refractive index gradient, and we find that the presence of the refractive index gradient leads to the appearance of a number of new soliton families. The effective coupling between the solitons and the localized linear eigenmodes of the lattice induces a drastic asymmetry in the soliton shapes and the appearance of long tails at the soliton wings. Such unusual solitons are found to be completely stable under propagation, and we report their experimental observation in fs-laser written waveguide arrays with focusing Kerr nonlinearity.
© 2014 Optical Society of America
Original Manuscript: April 8, 2014
Revised Manuscript: May 15, 2014
Manuscript Accepted: May 18, 2014
Published: June 13, 2014
Steffen Weimann, Yaroslav V. Kartashov, Victor A. Vysloukh, Alexander Szameit, and Lluis Torner, "Observation of asymmetric solitons in waveguide arrays with refractive index gradient," Opt. Lett. 39, 3694-3697 (2014)