Train of Ultrashort Mid-Infrared Pulses with Sub-Mrad Carrier-Envelope Phase Stability

Precise measurement and control of the frequency and phase of the electric-field carrier of ultrashort light pulses underneath their intensity envelope is instrumental to the study of dynamic processes unfolding on time scales shorter than the oscillation period of light, as well as for precision-spectroscopy measurements of quantum transitions. Among the techniques employed for the generation of trains of waveform-stable laser pulses, intra-pulse difference-frequency generation (IPDFG) is widely favored due to its passive carrier-envelope-phase (CEP) stabilization [1,2]. While in theory the CEP stability of IPDFG should be pristine, so far the lowest values reported for CEP noise measurements for trains of pulses generated via IPDFG lie in the range of a few tens of mrad [3], with - presumably - in most cases the metrology being the limitation rather than the IPDFG process itself.