Attosecond control of optical waveforms -: art. no. 116

A new, monolithic scheme for stabilizing the phase between the carrier wave and the envelope (CE phase) in a train of few-cycle laser pulses is demonstrated. Self-phase modulation and second-harmonic generation or difference-frequency generation in a single periodically poled lithium niobate crystal, that transmits the main laser beam, allows for the CE-phase locking directly in the usable output. The monolithic scheme obviates the need for splitting off a fraction of the laser output for CE-phase control, coupling into microstructured fibre, as well as separation and recombination of spectral components. As a result, the CE-phase error integrated over the spectral range of 0.2 mHz-35 MHz is as small as 0.016 x 2 pi rad. This implies that the phase of the field oscillations (lambda similar to 830 nm) with respect to the pulse peak is locked to within 44 attoseconds, resulting in optical waveform control with subhundred attosecond fidelity for the first time.