Femtosecond pump/supercontinuum-probe setup with 20 kHz repetition rate.

We developed a fast multichannel detection system for pump-probe spectroscopy, capable of detecting single shot super-continuum spectra at the repetition rate (10-50 kHz) of an amplified femtosecond laser system. By tandem pumping the amplifier with three pump lasers we obtain very low noise operation, with less than 0.1% rms intensity fluctuations at the output of the amplifier. We also propose an alternative way of chopping the pump beam. With a synchronized scanning mirror two spots in the sample are illuminated by the train of pump pulses in an alternating fashion, such that when both spots are interrogated by the probe pulse, the duty cycle of the experiment is doubled.