Laser induced soliton waveguides in lithium niobate crystals for guiding femtosecond light pulses

We show that efficient waveguides can be written by bright spatial solitons in lithium niobate photorefractive crystals by c.w. and pulsed laser beams. Using high repetition rate femtosecond laser pulses, an efficient formation of soliton waveguides is possible, after accumulating a large number of pulses, because the photo-excited carrier relaxation time is much longer than the pulse period. These results open the possibility of optimum waveguiding the femtosecond pulsed laser beams, the soliton waveguides creating a graded refractive index profile matched to the spatial beam profile. Our experiments show also very low pulse dispersion in these waveguides.