Phase coherence of modelocked femtosecond lasers

Summary form only given. We present direct measurement of the coherence of the carrier-envelope phase on the output of a stabilized Ti:sapphire laser. This is important for femtosecond technology, as the advent of few-cycle pulses makes it possible to study processes that are directly sensitive to the electric field of each pulse, rather than just the intensity envelope. These processes often display a threshold dependence on the electric field and hence are sensitive to the carrier-envelope phase of the light pulse making them attractive for measurement schemes that can used to determine the "absolute" carrier-envelope phase of a few cycle pulse. Such schemes usually require amplified pulse systems with repetition rates on the order of several kilohertz thus requiring the coherence in the carrier-envelope phase to be at least on the same order.