Affiliation:
1. Kansas State University
Abstract
We investigate the role of the Porras factor (or laser focusing effect) on the macroscopic high-order harmonic generation (HHG) driven by a focused broadband few-cycle laser beam. By employing a non-adiabatic phase-matching analysis method, we reveal that phase mismatch due to the induced-dipole phase varies with the Porras factor, which is dominant in phase matching at low gas pressure. We also find that in a strongly ionized medium when gas pressure is high, the nonlinear propagation is dominated by a plasma effect such that the focusing effect is mitigated, resulting in similar poor phase matching of HHG regardless of the Porras factor. Our results are expected to assist experimentalists identifying optimal conditions for HHG using ultrashort laser pulses.
Funder
National Natural Science Foundation of China
Postgraduate Research Practice Innovation Program of Jiangsu Province
Funding of NJUST
Natural Science Foundation of Jiangsu Province
Chemical Sciences, Geosciences and Biosciences Division, Office of Basic Energy Sciences, Office of Science, Department of Energy, USA
Subject
Atomic and Molecular Physics, and Optics