Abstract
We reexamine the resonance enhancement of a single harmonic emission during the propagation of ultrafast pulses through atomic and nanoparticle tin-containing laser-induced plasma (LIP). We compare the single atomic Sn and Sn nanoparticle plasmas to demonstrate a distinction in the enhancement factor of the single harmonic in the case of fixed and tunable near-infrared pulses. The analysis of the dynamics of Sn LIP shows the range of optimal delays between heating and driving pulses (130–180 ns), at which the maximal harmonic yield can be achieved. The enhancements of the 17th and 18th harmonics of 806 nm pulses were analyzed in the case of single-color and two-color pumps of LIP, showing up to a 12-fold enhancement of even harmonics in the two-color pump case. We show the enhancement of a single harmonic in the vicinity of the 4d105s25p2P3/2→4d95s25p2 transitions of Sn II ions and demonstrate how this process depends on the constituency of the plasma components at different conditions of target ablation. The application of tunable (1280–1440 nm) radiation allows for demonstrating the variations of single harmonic enhancement using a two-color pump of Sn-containing LIP.
Highlights
Resonance-related effects play an important role in different fields of laser physics and optics
We have compared the resonance-induced enhancement of single harmonic emissions during the propagation of ultrafast pulses through tin-containing laser-induced plasmas
The analysis of the dynamics of laser-induced plasma (LIP) produced on a Sn bulk target and a Sn NP target has shown the range of the optimal delays between heating and driving pulses (130–180 ns), at which the maximal harmonic yield can be achieved
Summary
Resonance-related effects play an important role in different fields of laser physics and optics. This spectrum was collected without the propagation of a 64 fs DP through the plasma plume and is shown for the demonstration of various emission lines from highly-ionized tin LIP The application of such plasma for HHG has two drawbacks: the first disadvantage is associated with strong incoherent radiation in the range of harm3oonfi1c4 generation, which can entirely overlap later radiation, and the second disadvantage is related to a deterioration of the optimal phase-matching conditions between driving and harmonic waves. The harmonics, in this case, originated from the atoms and ions of tin In these experiments, the femtosecond pulses were delayed with respect to those from the Nd: YAG laser to propagate through the formed plasma at a maximal density of the ejected particles. Notice that the efficiency of harmonics produced by shorter wavelength sources becomes higher due to the strong wavelength-dependent harmonic yield (Iharm ∞ λ−5) (Iharm is the harmonic intensity and λ is the driving field wavelength [46])
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