Manipulation of the length of Bessel femtosecond laser filamentation

The filamentation is particularly useful for many applications of ultrafast laser, and the manipulation of the length of filaments also has received a lot of attention. Precise manipulation of the length of filaments enables better implementation of a wide range of filament-based applications. We proposed a novel method to manipulate the length of and location of the Bessel filamentation by changing the apex angles of the axicon. The influence of apex angle on the spatial distribution of the filamentation had been demonstrated in detail. We also investigate the correlation between the length of the filament and the radial parameters of the Bessel laser beam. In addition, the physical mechanism underlying the manipulation of the filament length were discussed. Our results indicate that the length of the Bessel femtosecond laser filamentation can be manipulated precisely by changing the apex angle or adjusting the radius of the initial laser beam. This method is convenient manipulating the spatial properties of the filamentation for practical applications.