Phase stabilization of ultrashort optical pulses

New methods have recently been developed to measure the carrier-envelope phase evolution of ultrashort optical pulses. These methods utilize a powerful combination of time-domain and frequency-domain techniques. The resulting ability to stabilize the carrier-envelope phase of the pulse train emitted by a mode-locked laser means that the absolute frequencies in the optical spectrum can be determined, which has had an immediate impact on optical frequency metrology and optical clocks. In the time domain, this establishes the basis for controlling and tailoring the electric field of ultrashort pulses, which will affect applications in extreme nonlinear optics and coherent control. This paper provides a detailed look at the correspondence between time and frequency that underlies these results and reviews the recent progress in the field.