Plane waves are absolutely stable against small modulations in self-defocusing media, the dark spatial solitons exist only in the form localized dark hole on the plane wave background.

• 在自散焦介质中,平面波的传播对小的调制扰动是绝对稳定的,暗空间孤子正是作为平面波背景上的一种局域暗迹而存在的。