High-resolution Interferometric Diagnostics for Ultrashort Pulses

7. LATERAL SHEARING INTERFEROMETRY FOR HIGH-HARMONIC GENERATIONand interfered on a spatially resolved spectrometer. One of the sources is rotated, producing alateral displacement on the spectrometer. The lateral shearing interferogram so recorded encodesthe spatial phase of the field at the detector, minus the spherical wavefront introduced by propagationto this plane from the source. I presented a comprehensive set of measurements of thespatial phase and amplitude profiles of harmonics 13–25 in krypton as a function of the gas jetz position. Over most of the parameter range, the results agreed with a simulation based on thequantum-orbits model. Various single-atom and macroscopic effects play a role in producing theobserved profiles.This work raises many avenues for future research. Constrained by the available laser power,the experiments were limited to harmonics 13–25 in krypton, with the entire system being optimizedjust to get any signal at all. Dispersion and absorption dominated the macroscopic effects,preventing direct observation of the interplay of the single-atom response and the geometry. Noveleffects arising from nonlinear propagation of the laser were also not exhibited at these power levels.A higher power source would provide for more options in terms of the target gas species,intensity scan range and focusing geometry. The other noble gases also have lower absorptionand dispersion, and a greater range of harmonics would be produced.184