Analysis of the existence of one-dimensional dark and gray spatial solitons in l ogarithmically nonlinear media

The existence of dark and gray spatial solitons in logarithmically nonlinear media is investigated. It is shown that both dark and gray solitons are possible in corresponding nonlinear media. The spatial width for dark solitons is analyzed .It is revealed as follows: the beam width decreases dramatically with increasing power when the peak power is much lower, exhibiting the good nonlinear effects in such cases. The variation of beam width is slow at first and then becomes constant when the peak power continuously increases .