We show that a new class of optical solitons is possible in nonlinear periodic structures. These waves can propagate undistorted even though their power spectra lie well within the frequency band gap of the periodic structure and even though their carrier frequency is very close to the Bragg resonance. Analysis shows that these Bragg solitons can exhibit velocities which are orders of magnitude lower than the speed of light in the unperturbed medium.

• Received 7 December 1988

DOI:https://doi.org/10.1103/PhysRevLett.62.1746