Fig. 4: Medium length dependence.
From: High efficiency ultrafast water-window harmonic generation for single-shot soft X-ray spectroscopy
a Normalized soft X-ray spectra observed under different Ne gas lengths. The gas pressure was maintained at 205 Torr. b The yield (square dots with error bars) at 240 eV under different Ne gas lengths,which are averaged by 100 measurements. The size of error bars indicates a range of ±SD, which ~95% of the data lies in. SD, standard deviation. The black solid curve indicates the calculated result when the coherence length (Lcoh) was 13 times the absorption length (Labs) using formula (1) in Ref. 38. The laser intensity was 3.9 × 1014 W cm−2. The inset indicates the calculated absorption length for each photon energy in 205 Torr of Ne gas. (c) Electric field after different propagation lengths. d Simulated high-order harmonics spectra after different medium lengths. e Electric field waveform after propagation for a few-cycle waveform using the over driven method. f Spatial and temporal profiles of the driving laser field after 0.5-mm-long medium using the over driven method.
