Carrier-envelope phase shift caused by variation of grating separation.

The effects of variation of the grating separation in a stretcher on the carrier-envelope (CE) phase of amplified pulses are investigated. By translating one of the telescope mirrors in the stretcher with a piezoelectric transducer, it is found that a 1 mum change of the distance causes a 3.7+/-1.2 rad shift of the CE phase, which is consistent with theoretical estimations. The results indicate that optical mounts used for gratings and telescope mirrors must be interferometrically stable; otherwise their vibration and thermal drift will cause significant phase error. The CE phase drift was corrected by feedback controlling the grating separation.