Nanoparticle (NP) films of silver were prepared using nanosecond (ns) and femtosecond (fs) pulsed laser deposition (PLD) in vacuum. The flux and energy distribution of the ions in the plasma part of the ablation plume were measured using a Langmuir ion probe. The deposition energy efficiencies of ns and fs silver PLD were also compared. For equivalent thickness up to ∼3 nm the NPs made by ns-PLD are well separated and roughly circular, but for higher thicknesses the NPs begin to coalesce. For equivalent thickness up to 7 nm the fs films are comprised of well separated NPs, though the mean NP size and the surface coverage increase with equivalent thickness. The mean Feret diameter for both ns- and fs-PLD films increases with increasing equivalent solid-density thickness. The surface plasmon resonance peak was observed to red shift for both ns- and fs-PLD films as the equivalent solid-density thickness was increased from 1 nm to 7 nm.

Copper targets are irradiated in the ablation regime by pairs of equal, time-delayed collinear laser pulses separated on a timescale going from ~2 ps to ~2 ns. The ablation plume is characterized by ion probe diagnostic, fast imaging, and temporally and spatially resolved optical emission spectroscopy. The variation in the ablation efficiency with the delay between the pulses is analyzed by measuring the ablation crater profile with a contact profilometer. The second laser pulse modifies the characteristics of the plasma plume produced by the first pulse and the ablation efficiency. The different mechanisms involved in double pulse ultrafast laser ablation are identified and discussed. The experimental findings are interpreted in the frame of a simple model of the interaction of the second pulse with the nascent ablation plume produced by the first pulse. This model yields consistent and quantitative agreement with the experimental findings predicting the observed experimental trends of the ablation depth reduction and ion yield increase with the delay between the pulses, as well as the characteristic timescale of the observed changes. The possibility of controlling the characteristics of the plumes produced during ultrafast laser ablation via an efficient coupling of the energy of the second pulse to the various ablation components produced by the first pulse is of particular interest in ultrafast pulsed laser deposition and microprobe analyses of materials

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Nanoparticle gold films were deposited using femtosecond laser ablation in argon at atmospheric pressure in an arrangement where a flat Au target was irradiated through a transparent substrate in close proximity. Spatially extended films were made by rastering the target and substrate assembly together in the laser beam. Fast imaging clearly showed pronounced narrowing of the ablation plume, which can be understood in terms of laser induced multiphoton ionisation and heating of the gas near the ablation site. Deposition was possible for target-substrate separation up to 2 mm. The equivalent thickness of the nanoparticle film was controlled in the range 0.4–28 nm by changing the target-substrate separation and the shot-to-shot spacing of ablation spot raster. The mean Feret diameter varied in the range 14–40 nm depending on the deposition conditions, and all the films showed a surface plasmon resonance at about 525 nm, which was nearly independent of the equivalent thickness. The technique can readily be applied to other materials for the fabrication of nanoparticulate films at atmospheric pressure.

This paper describes the results of an experimental and theoretical investigation of the physical origin of the visible continuum emission usually observed in the early stages of nanosecond laser ablation of solid materials. It has been suggested, but not confirmed, that the continuum is due to radiative recombination and bremsstrahlung emission. Time and space-resolved emission spectroscopy with an absolutely calibrated spectrometer was used to study the spectral emission in laser ablation of zinc in vacuum at 4.1 J cm -2 using a 8 ns, 1064 nm laser pulse. By modeling the spectral emission with a spectral synthesis code, it has been shown that the continuum emission is primarily due to bound-bound transitions between strongly Stark broadened energy levels. Similarly, it can be concluded that the optical absorption is primarily due to bound-bound transitions.