3-DIMENSIONAL DARK SPATIAL SOLITARY WAVES IN SATURABLE NONLINEAR DEFOCUSING MEDIA

Three-dimensional dark spatial solitary waves of the TM type are found to exist in a uniform saturable self defocusing nonlinear medium only within a certain range of the beam effective index n(eff) which may be wider or narrower compared with the corresponding one in the Kerr law medium, depending on nonlinear saturation index. This contrasts with the TE type, the existence of which in a saturable nonlinear medium is limited in the range of n(eff) equal to or narrower than that in the Kerr law nonlinear medium. The physical mechanism behind the distinct contrast is also discussed.