抄録
It was found in many experiments that repeated irradiations of short pulse lasers could form periodic
nano-structures on metal surfaces and many formation mechanisms were suggested, but it is not fully
understood yet. Therefore we use the two-dimensional PIC (Particle-In-Cell) code, in which equations
of motion for charged particles and Maxwell equations for electromagnetic fields are simultaneously
computed in two-dimensional space and three-dimensional velocity space, to simulate laser-plasma
interactions and to investigate the formation mechanism of the nanostructure. When the laser intensity is
relativistic, magnetic field and current density develop typical structures of the Weibel instability and it
is found that this instability plays an important role to form the periodic nano-structure. On the other
hand, it is also found that bi-directional surface plasma waves play a significant role together with the
oscillating two-stream instability in the case of non-relativistic laser intensity.
