We describe the programmable spatial beam shaping of 100-kHz, 4-µJ amplified femtosecond pulses in a focal plane by wave-front modulation. Phase distributions are determined by a numerical iterative procedure. A nonpixelated optically addressed liquid-crystal light valve is used as a programmable wave-front tailoring device. Top-hat, doughnut, square, and triangle shapes of 20-µm size are obtained in a focal plane. Their suitability for femtosecond laser machining is demonstrated.
© 2005 Optical Society of America
(070.2580) Fourier optics and signal processing : Paraxial wave optics
(140.3300) Lasers and laser optics : Laser beam shaping
(140.7090) Lasers and laser optics : Ultrafast lasers
(230.3720) Optical devices : Liquid-crystal devices
Nicolas Sanner, Nicolas Huot, Eric Audouard, Christian Larat, Jean-Pierre Huignard, and Brigitte Loiseaux, "Programmable focal spot shaping of amplified femtosecond laser pulses," Opt. Lett. 30, 1479-1481 (2005)