Multiple filamentation generated by focusing femtosecond laser with axicon.

Multiple filamentation has been observed when focusing a femtosecond laser pulse into a methanol solution with an axicon. It is found that multiple long filaments are located on the central spot and ring structures of the quasi-Bessel beam created by the axicon. Since the quasi-Bessel profile is determined by the axicon properties, the axicon has been suggested as a simple optics to control multiple filaments.