Three-wave envelope solitons: possibility of controlling the speedof light in fiber

Theory predicts that three-wave envelope solitons (TWES) can he generated in dual-mode optical fibers by simultaneous injection of two copropagating optical modes. The mechanism of the three-wave interaction is the recently observed intermodal forward stimulated Brillouin scattering (FSBS). The dynamics of soliton generation depends on the duration of the injected pulses, the pump power, and the attenuation time constant. For the adiabatic modulation of injected optical waves, a new type of generation has been analyzed: an acoustical wave structure that scatters the incident pump into the Stokes wave is formed in the fiber prior to and after the soliton generation. This structure appears as a result of FSBS and serves as a TWES “launcher.” We identify this type of generation in earlier soliton experiments in stimulated Raman scattering. The TWES velocity depends on the pump power. For a typical dual-mode fiber, the speed of TWES can be adjusted over four orders of magnitude by adjusting the pump power between 0.01 and 200 mW. The duration of the soliton is <3 ms due to the acoustic attenuation. The length of the fiber can be shorter than the length of the soliton while preserving the same TWES characteristics. Both Ar⁺ and Nd:YAG lasers are suitable for TWES generation