Femtosecond propagation dynamics of intense light pulse in air observed by FTOP

Summary form only given. The ultrafast propagation dynamics of intense femtosecond laser pulses in under-dense plasmas have recently been attracting much interest, but the measurement methods used have been indirect ones such as the Schlieren method and have each had a slow-time resolution. Very recently, however, we proposed a novel, direct, and ultrafast measurement method called femtosecond time-resolved optical polarigraphy (FTOP). We report interesting phenomena in the propagation of intense femtosecond pulses in the atmosphere. By using FTOP, the self-modulated complex motions of the pulses can be visualized at an ultrafast temporal resolution.