GENERATION OF 135-FS PULSES OF VARIABLE PULSE FRONT TILT BY SPATIALLY-EVOLVING CHIRPED-PULSE AMPLIFICATION AT 248-NM

It has been shown previously that a spatially dependent negative chirp develops, accompanied by a titled pulse front, when a pulse traverses a single dispersive element. In case of a positively chirped pulse perfect pulse compression can be achieved at a certain plane. In this paper it is demonstrated experimentally that this plane can be imaged, preserving the compressed pulse duration in the plane of the image, and allowing a continuous change of the pulse front tilt through the variation of the magnification. With the insertion of an amplifier just before the imaging element, spatially-evolving chirped-pulse amplification is accomplished. Consequently the amplifier sees a stretched pulse, hence a lowered peak power, while a single lens (or mirror) following the amplifier is enough to create the desired pulse front with the minimum pulse duration at the position of a target. With the use of this technique 248 nm, 135 fs pulses are created at the target plane while the pulse duration in the amplifier is several ps. The spatial evolution of the chirp and of the temporal and spectral properties of the pulse is followed. © 1990.