The chirp rate of harmonics 13 to 23 in argon was measured by cross correlation with a 12 femtosecond probe pulse. The negative chirp was directly measured under low ionization conditions due to the atomic dipole phase. It was showed that the additional chirp on the pump pulse was transferred to the qth harmonic as q times the fundamental chirp. The attosecond pulse trains synthesized from these harmonics had a pulse spacing that increased linearly with time.
Publication Source (Journal or Book title)
Physical Review A - Atomic, Molecular, and Optical Physics
Mauritsson, J., Johnsson, P., López-Martens, R., Varjú, K., Kornelis, W., Biegert, J., Keller, U., Gaarde, M., Schafer, K., & L'Huillier, A. (2004). Measurement and control of the frequency chirp rate of high-order harmonic pulses. Physical Review A - Atomic, Molecular, and Optical Physics, 70 (2) https://doi.org/10.1103/PhysRevA.70.021801