Long-term CEP-stable high energy few-cycle pulses using the feed-forward method

The feed-forward technique has recently revolutionized carrier-envelope phase stabilization, enabling unprecedented values of residual phase jitter. Nevertheless, in its original demonstrations the stabilized beam exhibited angular and temporal dispersion. We demonstrate that these problems can be solved, resulting in few-cycle pulses with good beam quality. This in turn enables the use of monolithic interferometers, providing excellent long-term stability of the system. Out-of-loop RMS phase noise of less than 80 mrad over 33 minutes (0.5 mHz to 5 kHz) is measured, i.e., a value that has previously been reported for a few seconds integration time. The current method promises to enable reliable operation of CEP-stable systems over several days.