We investigate spatial solitons in a resonator with a narrow-band gain element and a saturable absorber placed in Fourier-conjugated resonator planes. Solitons are stationary or move at discrete velocities depending on the resonator tuning. The modulus of the velocity of moving solitons is fixed, but the direction of their motion is arbitrary. Solitons compete in velocity space. The experiments are conducted on a photorefractive oscillator with bacteriorhodopsin saturable absorber. Observations agree well with solutions of a general order parameter equation for such resonators.

• Received 17 July 1997

DOI:https://doi.org/10.1103/PhysRevA.57.599