With time-dependent density functional theory and molecular dynamics excitations of linear and rhombic C₄ in intense laser field are explored.It is found that electrons of 1incar C₄ obtain mote enelrgy while ions of rhombic C₄ get more from the 1aser filed. Ionization is enhanced as C₄ owns 8 linear structure. As laser polarization is along the x axis there is only D_x excitation of a linear C₄ while dipole oscillations of a rhombic C₄ in x and y directions are excited.

A Scalar wave equation with an aix direction variate z is used to describe a single-mode taper fiber, and the scalar wave equation is changed to one-order differential equations group by a Simple transform. The quartic Runge-kutta Method improved by Gill is used to Calculate the propagation Characters of a Single-mode taper fiber.