Conductivity and discharge guiding properties of mid-IR laser filaments

Abstract

The electric properties of mid-IR filaments in air have been investigated in comparison with their more traditional near-IR counterparts. Although the number of ions left after the pulse is similar for both spectral regions, filaments at 3.9 µm produce lower electron densities and lower-pressure depression, which prevent them in the present conditions (25 mJ, 90 fs) to trigger or guide HV discharges (130 kV over 12 cm). We conclude that mid-IR filaments require significantly higher energy/power levels than their near-IR counterparts for applications related to lightning control and for fully taking advantage of their unique propagation properties (single, large diameter filaments over long distances).