title: Bright and dark simultons in second-harmonic generation.
abstract: A symbiotic pair of dark (second-harmonic) and bright (fundamental frequency) solitons sustain each other and travel locked in second-harmonic generation dominated by group-velocity difference or spatial walk-off. The conditions of existence of the soliton pair are determined, and its stability in the presence of dispersion is discussed.
authors.forename: S
authors.initials: S
authors.lastname: Trillo