Air hydrodynamics of the ultrafast laser-triggered spark gap

TL;DR

This paper investigates the air hydrodynamics caused by ultrafast laser pulses in spark gaps, comparing plasma-based and plasma-free methods, revealing the dominant role of laser-induced air density depression in gap breakdown.

Contribution

It provides detailed space and time resolved measurements of air hydrodynamics in laser-triggered spark gaps, introducing novel insights into the mechanisms of gap evolution.

Findings

Laser-induced air density depression dominates gap evolution.

Both plasma-based and plasma-free excitation methods are characterized.

Cumulative effects of laser pulses influence breakdown processes.

Abstract

We present space and time resolved measurements of the air hydrodynamics induced by ultrafast laser pulse excitation of the air gap between two electrodes at high potential difference. We explore both plasma-based and plasma-free gap excitation. The former uses the plasma left in the wake of femtosecond filamentation, while the latter exploits air heating by multiple-pulse resonant excitation of quantum molecular wavepackets. We find that the cumulative electrode-driven air density depression channel initiated by the laser plays the dominant role in the gap evolution leading to breakdown.