We introduce the concept of soliton clusters—multisoliton bound states in a homogeneous bulk optical medium—and reveal a key physical mechanism for their stabilization associated with a staircaselike phase distribution that induces a net angular momentum and leads to cluster rotation. The ringlike soliton clusters provide a nontrivial generalization of the concepts of two-soliton spiraling, optical vortex solitons, and necklace-type optical beams.

• Received 19 June 2001

DOI:https://doi.org/10.1103/PhysRevLett.88.053901