Nonlinear optics with phase-controlled pulses in the sub-two-cycle regime

Summary form only given. Very recently, two groups have observed and stabilized the pulse-to-pulse carrier-envelope phase slip /spl Delta//spl phi/ by spectrally broadening femtosecond laser pulses in an external optical fiber. In this paper we report the determination and stabilization of /spl Delta//spl phi/ using pulses obtained directly from a mode-locked laser itself. We have done this both by monitoring the coherent interference of the fundamental pulse with its second harmonic and by observing a similar interference between the second and third harmonic.