Engineering topics

Charalambidis, D

Publications and source records attributed to Charalambidis, D.

3 records

DOE OSTI2010

Measuring the absolute carrier-envelope phase of many-cycle laser fields

The carrier-envelope phase (CEP) of high-peak-power, many-cycle laser fields becomes a crucial parameter when such fields are used, in conjunction with polarization gating techniques, in isolated attosecond (asec) pulse generation. However, its measurement has not been achieved so far. We demonstrate a physical process sensitive to the CEP value of such fields and describe a method for its online shot-to-shot monitoring. This work paves the way for the exploitation of energetic isolated asec pulses in studies of nonlinear extreme ultraviolet (XUV) processes and XUV-pump-XUV-probe experiments with asec resolutions.

74 ATOMIC AND MOLECULAR PHYSICS↗

DOE OSTI2010

Persistent quantum interfering electron trajectories

The emission of above-ionization-threshold harmonics results from the recombination of two-electron wave packets moving along a ''short'' and a ''long'' trajectory in the atomic continuum. Attosecond pulse train generation has, so far, been attributed to the short trajectory, attempted to be isolated through targeted trajectory-selective phase-matching conditions. Here, we provide experimental evidence for the contribution of both trajectories to the harmonic emission, even under phase-matching conditions unfavorable for the long trajectory. This is finger printed in the interference modulation of the harmonic yield as a function of the driving laser intensity. The effect is also observable in the sidebands, which arise from the frequency mixing of the harmonics and the driving laser field, an effect with consequences in cross-correlation pulse metrology approaches.

74 ATOMIC AND MOLECULAR PHYSICS↗

DOE OSTI2010

Inconsistencies between two attosecond pulse metrology methods: A comparative study

The two basic approaches underlying most of the metrology of attosecond pulse trains are compared in the spectral region {approx}14-24 eV, that is, the second-order intensity volume autocorrelation and the resolution of attosecond beating by interference of two photon transitions (RABITT). They give rather dissimilar pulse durations. It is concluded that for the present experimental conditions RABITT may underestimate the duration under measurement, due to variations of the driving intensity, but in conjunction with theory allows an estimation of the relative contributions of two different electron trajectories to the extreme-ultraviolet (XUV) radiation.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗