Observation of discrete quadratic solitons

Discrete solitons with two frequency components mutually locked by a quadratic nonlinearity have been observed for the first time. Optical experiments have been performed in arrays of coupled channel waveguides with tunable cascaded quadratic nonlinearity. The tunability was the prerequisite that soliton species with different topology could be identified in the same array. Moreover, soliton stability has been experimentally probed. Good agreement with theoretical predictions was found.