DARK SPATIAL SOLITONS IN NON-KERR-LAW MEDIA

Two-dimensional light trapping of TM and TE patterns in saturable self-defocusing nonlinear media is examined. The vector dark spatial soliton of TM type is found to exist only within a certain range of the beam effective index, which can be wider or narrower compared with the corresponding one in the Kerr-law nonlinearity, depending on the nonlinear saturation index. This contrasts with the scalar dark spatial soliton of TE type, the guidable region of which in saturable nonlinear media is equal to or narrower than that in the Kerr-law nonlinear medium. The physical origin leading to such a distinct contrast is also explored.