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.

© 2023 Optica Publishing Group

Generation of high-order harmonics and attosecond pulses in the water window via nonlinear propagation of a few-cycle laser pulse

Bonggu Shim, Garima C. Nagar, Yi Wu, and Zenghu Chang
Opt. Express 31(20) 32488-32503 (2023)

Carrier-envelope-phase insensitivity in high-order harmonic generation driven by few-cycle laser pulses

C. Hernández-García, W. Holgado, L. Plaja, B. Alonso, F. Silva, M. Miranda, H. Crespo, and I. J. Sola
Opt. Express 23(16) 21497-21508 (2015)

Phase sensitivity of high-order harmonic generation with few-cycle laser pulses

Gabriel Tempea, Michael Geissler, and Thomas Brabec
J. Opt. Soc. Am. B 16(4) 669-673 (1999)

Brunel harmonics generated from ionizing clusters by few-cycle laser pulses

Xiaohui Gao, Bonggu Shim, and Michael C. Downer
Opt. Lett. 44(4) 779-782 (2019)

Optimization and phase matching of fiber-laser-driven high-order harmonic generation at high repetition rate

Amélie Cabasse, Guillaume Machinet, Antoine Dubrouil, Eric Cormier, and Eric Constant
Opt. Lett. 37(22) 4618-4620 (2012)