Direct CEP Stabilization of a High-Repetition Rate, Few-Cycle OPCPA Chain with a Single Feedback Loop, Employing a Stereo-ATI

Today's Carrier-Envelope Phase (CEP) stabilizations of mode-locked oscillators widely used in attosecond science and frequency metrology rely on octave spanning frequency combs and the detection of beating between the blue end and the frequency doubled red end of the same spectrum. This technique was established by the seminal works of Hänsch and co-workers [1], demonstrating the stabilization of optical frequencies from such a frequency comb by transferring the slippage of the CEP (or carrier-envelope offset frequency) into a detectable radio frequency by f-2f interferometry. The requirement of an octave spanning spectrum means that usually some kind of super-continuum generation is involved, which, in practice often is a fragile scheme since wide band oscillators are very prone to instabilities and noise.