Abstract

Propagation of a light beam in a nonlinear medium has been a subject of great interest over the last three decades. In a uniform medium, the nonlinearity has been shown to have such an effect to offset the diffraction of a beam, leading to the stationary propagation of a CW wave.^1-6 In an optical fiber where a light beam is bounded by the linear guiding structure, the nonlinearity can produce a balancing effect to the dispersion of a pulsed beam to yield the stationary propagation of the pulse.^7,8 In most experimental situations of light self trapping, pulsed lasers are used as sources for excitation, especially when high power operation is involved.^9-11 In these circumstances, a beam of light will experience both diffraction and dispersion in addition to self-focusing (defocusing) and self phase modulation that result from nonlinearity. In a self-focusing uniform medium, it has been shown that the nonlinearity can compensate for both the diffraction and anomalous dispersion simultaneously to result in stationary propagation of the bright pulsed self-trapped beams (light bullets that evolve without change in space and time).¹² In the Kerr-law medium, this stationary state of light bullets is unstable. A perturbation will lead to collapse of the light bullet.¹² Nevertheless, in a saturable nonlinear medium the collapse can be bounded and the bounding may lead to the formation of stable, nondiffracting and nondispersing bright pulses.¹²

© 1995 Optical Society of America