CEP-Stable Generation of Close to Single-Cycle and Ultrashort UV Pulses at 800 kHz Repetition Rate using a Gas-Filled Hollow-Core PCF

Ultrashort laser pulses at high repetition rates are a fundamental tool in a wide range of applications in strong-field physics and attosecond science, where particular attention has to be given to the stability of the carrier to envelope phase (CEP) of the ultrashort optical waveform. Here we report the generation of close to single-cycle pulses with stable CEP at 800 kHz repetition rate, obtained via soliton-effect self-compression in a gas-filled kagomé-type hollow-core photonic crystal fibre (kagomé-PCF). In addition, we have measured for the first time the CEP stability of soliton-emitted dispersive waves (DWs) lying in the ultraviolet spectral region.