Control of laser-beam propagation and absorption in a nanoplasma gas by programming of a transient complex refractive index with a prepulse

Abstract

By utilizing the intensity- and duration-dependent heating and expansion rate of nanoplasma to generate a transient transverse gradient of the refractive index, prepulse controlled laser-beam propagation is demonstrated. The dynamical response of the macroscopic optical refractive index is traced back to the microscopic polarizability of nanoplasmas experimentally, in accordance with hydrodynamic nanoplasma models. In particular, the delay between the prepulse and the main pulse for maximum Rayleigh scattering is found to be longer than that for maximum x-ray emission, supporting the more refined one-dimensional self-consistent hydrodynamic nanoplasma model.

Clustered gases as a medium for efficient plasma waveguide generation

“…Thus, the process of selffocusing of the pulse is accompanied by its efficient absorption. The predictions of the model for the complex polarizability, self-focusing and frequency shifts have been experimentally confirmed (Kim et al 2003a(Kim et al , 2005Alexeev et al 2003;Chu et al 2004). The combination of highly efficient absorption with weak selffocusing of femtosecond pulses makes possible the generation of femtosecond end-pumped waveguides that are much longer than the Rayleigh range of the focused pulse.…”

“…Clusters are van der Waals-bonded assemblies of approximately 10 2 -10 7 atoms produced by rapid cooling during high-pressure gas flow through a gas jet nozzle into vacuum (Hagena & Obert 1972;Hagena 1987). A clustered gas introduces two novel and important features: efficient absorption of femtosecond pulses (Ditmire et al 1997;Kim et al 2003a,b) and their self-guided propagation (Alexeev et al 2003;Chu et al 2004). The laser breakdown of a cluster is initiated by OFI, which produces the first generation of free electrons, followed by efficient collisional ionization under local solid density conditions, where the local atomic density N 0 is approximately 1000 times greater than in typical gas targets.…”

Effect of self-focusing on laser third harmonic generation in a clustered gas

“…These results have been interpreted as a consequence of transient polarizability of clusters. Chu et al [22] have carried out another fascinating experimental study on laser self-focusing in clustered argon jet. They employ a prepulse prior to the main pulse.…”