A dark stripe is generated when the partially spatially incoherent beam passes through amplitude mark.Based on bulk photovoltaic effect in LiNbO3:Fe crystal,one-dimensional even-number sequence of solitons with partially spatially incoherent beam is written in crystal without background illumination.When the width of the dark stripe is 13.4 μm,the stripe only splits into Y-junction solitons.However,the dark stripe splits into quadratic-solition when the width of the dark stripe is 20.1 μm.The ex...