Ionization rate and plasma dynamics at 3.9 micron femtosecond photoionization of air

Abstract

The introduction of mid-IR optical parametric chirped pulse amplifiers (OPCPAs) has catalyzed interest in multi-millijoule, infrared femtosecond pulse-based filamentation. As tunneling ionization is a fundamental first stage in these high-intensity laser-matter interactions, characterizing the process is critical to understand derivative topical studies on femtosecond filamentation and self-focusing. Here, we report constructive-elastic microwave scattering-based measurements of total electron count, electron number densities, and photoionization rates generated by 3.9 micron femtosecond mid-infrared tunneling ionization of atmospheric air. Consequently, we determine photoionization rates in the range of 5.0x10${}^8$-6.1x10${}^9$ s${}^{-1}$ for radiation intensities 1.3x10${}^{13}$-1.9x10${}^{14}$ W/cm${}^2$, respectively. The proposed approach paves the wave to precisely tabulate photoionization rates in mid-IR for broad range of intensities and gas types and to study plasma dynamics at mid-IR filamentation.

References in corpus (3)

• Bright Coherent Ultrahigh Harmonics in the keV X-Ray Regime from Mid-Infrared Femtosecond Lasers
• Absolute measurement of laser ionization yield in atmospheric pressure range gases over 14 decades
• Conductivity and Discharge Guiding Properties of Mid-IR Laser Filaments