Investigation of a grating-based stretcher/compressor for carrier-envelope phase stabilized fs pulses.

In this work, we experimentally investigate the effect of a grating based pulse stretcher/compressor on the carrier-envelope phase stability of femtosecond pulses. Grating based stretcher-compressor (SC) setups have been avoided in past demonstrations of chirped pulse amplification (CPA) of carrier envelope phase (CEP) stabilized femtosecond pulses, because they were expected to introduce significantly stronger CEP fluctuations than material-based SC systems. Using a microstructure fiber-based detection setup, we measure CEP fluctuations of PhiCE,SC = 340 milliradians rms for a frequency range from 63 mHz to 102 kHz for pulses propagating through the SC setup. When bypassing the beam path through the SC, we find CEP fluctuations of PhiCE,bypass = 250 milliradians rms. These values contain significant contributions from amplitude-to-phase conversion in our microstructure fiber-based detection setup for PhiCE. Hence, we do not unambiguously measure any added CEP noise intrinsic to the SC setup. To distinguish between intrinsic SC effects and amplitude-to-phase conversion, we introduce controlled beam pointing fluctuations alpha and again compare the phase noise introduced when passing through / bypassing the SC. Our measurements do not reveal any intrinsic effects of the SC system, but allow us to place an upper limit on the sensitivity of our SC system of PhiCEintrinsic,SC / alpha < 13000 rad/rad. Our results demonstrate experimentally that there is not a strong coupling mechanism between CEP and beam pointing through a stretcher/compressor , as well as measuring significantly smaller CEP fluctuations than experimental results reported previously.