Plasma formation thresholds of solid targets irradiated with laser pulses of ~10–12 and ~10–10 s duration (wavelength λ = 1.06 μm)

The plasma formation thresholds were determined for metal (Al, Cu) and dielectric (K8 glass, KV quartz) targets irradiated with laser pulses (λ = 1.06 μm, τ = 10^–12 and ~10^–10 s). It was found that the lowest surface energy density ε_* needed to form a plasma decreased by two orders of magnitude, compared with the case of interaction of radiation characterised by the parameters λ = 10.6 μm and τ ~10^–6 s. An analysis of the results indicated that the ‘short’ thermal model of plasma initiation remains valid in the τ ~10^–12 — 10^–10 s range of durations.