National Research Council of Canada. Security and Disruptive Technologies
The physics of attosecond pulse generation requires using infrared driving wavelength to reach the soft X-rays. However, with longer driving wavelength, the harmonic conversion efficiency drops significantly. It makes the conventional attosecond pulse measurement using streaking very difficult due to the low photoionization cross section in the soft X-rays region. In-situ measurement was developed for precisely this purpose. We use in-situ measurement to characterize, in both space and time, an attosecond pulse produced by ultrafast wavefront rotation of a 1.8 μm fundamental beam. We confirm what models suggest – that each beamlet is an isolated attosecond pulse in the time domain. We get almost constant flat wavefront curvature through the whole photon energy range. The measurement method is scalable to the soft X-ray spectral region.