Optimization of a hollow-core fiber based nonlinear pulse compressor for a compact kHz laser wakefield accelerator*

MeV electron beams from a compact laser plasma accelerator can be used for a number of applications, such as Bremsstrahlung x-ray imaging and ultrafast electron diffraction. The commercially available laser systems, which offer kHz pulses with duration of tens fs and mJ energy, are insufficient to fulfill the resonant condition for the laser wakefield acceleration and require temporal compression. We report on nonlinear compression of a commercial Ti:Sapphire laser from ~40 fs to <4 fs in a hollow-core fiber compressor with 60% overall energy transmission efficiency. We show that controlling the nonlinearity prior to coupling into the fiber proves to be critical to achieve high energy transmission. Through third order dispersion tuning, a peak power above 1 TW was achieved, enabling acceleration of electrons to MeV energy level at kHz repetition rate.