Multiple foci and a long filament are observed when we focus a femtosecond laser pulse into a fused-silica sample. The dependences of the intensity distribution of the plasma luminescence on the pulse energy and the numerical aperture (NA) of the focusing objective are investigated. Multiple foci are observed when NA of ≤0.65 . A long filament tail is formed instead of multiple foci when the NA is 0.85. A physical image of femtoseond pulse propagation is given by a model based on the nonlinear Schrödinger equation.
© 2002 Optical Society of America
(190.5530) Nonlinear optics : Pulse propagation and temporal solitons
(190.7110) Nonlinear optics : Ultrafast nonlinear optics
(220.4000) Optical design and fabrication : Microstructure fabrication
(320.7130) Ultrafast optics : Ultrafast processes in condensed matter, including semiconductors
Zhaoxin Wu, Hongbing Jiang, Le Luo, Hengchang Guo, Hong Yang, and Qihuang Gong, "Multiple foci and a long filament observed with focused femtosecond pulse propagation in fused silica," Opt. Lett. 27, 448-450 (2002)