Suppressing Temporal Pedestal in Nd:glass Laser Systems by Avoiding Far-Field Spectral Phase Noise

The impact of spectral phase noise on the temporal pulse contrast is explored experimentally by using two zero-dispersion stretchers (Offner stretcher and two-lens stretcher). The results show clearly that a long temporal pedestal appears when there exists far-field spectral phase noise, which greatly degrades the pulse contrast. In our proof-of-principle experiment, by using a two-lens stretcher, the far-field spectral phase noise is avoided and the noise pedestal of the amplified pulse in a Nd:glass laser system is reduced, with the contrast reaching a level of 10
^-11
in the 60-ps time window before the main pulse. This simple method may pave the way in a PW-level Nd:glass laser by directly using pre-cleaning techniques.