Self-focusing of low intensity CW laser radiation in nickel alloy coated beam splitter

Self-focusing of 488 nm laser radiation with intensity around 42 W/cm/sup 2 /has been observed in a nickel alloy coated beam splitter. The experimental results demonstrate that laser self-focusing occurs when the beam passes through the interface between the glass substrate, implying that a layer of nonlinear medium has been generated at the interface. The experimental results also indicate that the mechanism of the self-focusing is optic-thermal effect.