Observation of the transverse pinch of the expansion of an femtosecond laser-plasma

Using Normaski polarization interference technique, the expansion process of a plasma generated by ultrashort laser pulses was optically diagnosed. Temporal resolved interferogram of the laser-plasma has been obtained. A strong pinch effect in the transverse dimension has been observed for a jet expansion of the laser- plasma. It is found that the pinch effect was due to the confinement of the magn etic fields generated in the laser-plasma.