Steady-state spatial solitons in biased photovoltaic-photorefractive crystals for short circuits

A theory on spatial solitons in photovoltaic (PV)-photorefractive (PR) crystals for short circuits is developed that gives rise to spatial solitons due to both a bulk PV effect and spatial nonuniform screening of the external field. When the PV effect is neglected these solitons are screening solitons. When the external field is absent these solitons are PV solitons in short and open circuits and it is predicted that grey solitons exist in PV-PR crystals for short circuits. We also show theoretically that PV nonlinearity can be switched from self-defocusing to self-focusing (or vice versa) by adding the external field.