Abstract
Studies of high-power ultrashort laser pulse interaction with matter are not only of fundamental scientific interest, but are also highly relevant to applications in the domain of remote sensing. Here, we investigate the effect of laser wavelength on coupling of femtosecond laser filaments to solid targets. Three central wavelengths have been used to produce filaments: 0.4, 0.8, and 2.0 µm. We find that, unlike the case of conventional tight focusing, use of shorter wavelengths does not necessarily produce more efficient ablation. This is explained by increased multi-photon absorption arising in near-UV filamentation. Investigations of filament-induced plasma dynamics and its thermodynamic parameters provide the foundation for unveiling the interplay between wavelength-dependent filament ablation mechanisms. In this way, strategies to increase the sensitivity of material detection via this technique may be better understood, thereby improving the analytical performance in this class of applications.
Highlights
Performing LIBS at large standoff distances leads to two main challenges associated with beam delivery: Prohibitively large optics Absorption and atmospheric turbulence
Fundamental harmonic of the laser is set at ~800 nm; The second harmonic (0.4 μm) is created within BBO crystal (β-BaB2O4); 2.0 μm radiation is produced via Optical Parametric Amplification (OPA)
Detailed fundamental studies performed on solid targets serve as a basis to investigating relevant thermodynamic parameters and plasma emission properties of nuclear materials;
Summary
Performing LIBS at large standoff distances leads to two main challenges associated with beam delivery: Prohibitively large optics Absorption and atmospheric turbulence. OPTICAL (REMOTE) SENSING FOR NONPROLIFERATION, SAFEGUARDS, AND VERIFICATION Spot size (diffraction limited): Self-focusing: collection in-situ detection analysis / verification Generating 0.4 μm and 2.0 μm laser radiation
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