Time-domain stabilization of carrier-envelope phase in femtosecond light pulses

We report a time-domain method of stabilizing the carrierenvelope phase (CEP) of femtosecond pulses. Temporal variations of the pulse envelope and the carrier electric-field phase were separately detected with the aid of intensity cross-correlation and interferometric crosscorrelation. These detected signals were used to stabilize the CEP; the resulting 50-fold improvement in the fractional stability of the carrierenvelop-offset frequency was evaluated as 1.2 × 10-11 at 0.1 second averaging periods and 1.7 × 10-9 at 80 seconds, corresponding to a carrier envelope phase noise of 75 microradians and 10 milliradians, respectively. This method can be realized with a low pulse energy of ∼10 pJ and does not require subsequent power amplification or spectral broadening. The high efficiency and short-term stability of this method can facilitate the use of femtosecond lasers in the field of industrial surface measurements, telecommunications, and space sciences.