Extremely broadened high-order harmonics generated by the femtosecond pulses propagating through the filaments in air

Abstract

We demonstrate a considerable broadening of the harmonics generating in laser plasma using the laser pulses propagating through the filaments in air. A fourfold increase of harmonic bandwidth was achieved in the case of phase-modulated laser pulses, alongside with an increase in harmonic conversion efficiency (from 5×10−6 to 1.2×10−5). We also present the studies of harmonic generation using phase-modulated pulses at different ranges of ellipticity of the polarization of laser beam.

Harmonic generation in laser-produced plasmas containing atoms, ions and clusters: a review

“…Spatial shapes of (a) laser beam after compressor and (b) laser beam after propagation of the telescope and filaments. Here, the corresponding spectral distributions of laser pulses for these two cases are also presented (from [49]). 9.…”

“…One should expect that propagation of a focused intense laser pulse through air might also cause a significant SPM-induced broadening of the driving pulse and a remarkable change of the harmonic pattern during the HHG in laser plasma using this radiation. In this section, the harmonic spectra obtained during the HHG in silver plasma are analysed when very broad harmonics were observed in the case of focusing of the narrowband laser radiation in air prior to the generation of harmonics in the laser plume [49]. The schemes for laser ablation were analogous to those used in plasma HHG.…”

“…Among them are the studies of harmonics from clusters using the ablation of commercially available nanoparticles [42,43], fullerenes [44][45][46] and carbon nanotubes [47], resonanceenhanced features of odd and even harmonics [48], generation of extremely broadband high-order harmonics [49], application of high pulse repetition rate laser sources and ultrashort pulses for HHG in plasma plumes [32], observation of quantum path signatures in the harmonic spectra from various plasmas [33], enhancement of harmonics from in situ-produced clusters [50], development of few theoretical approaches describing the observed peculiarities of resonance-enhanced harmonics [51][52][53][54][55][56], emergence of a 'second' plateau in the harmonic distribution [57], development of the two-colour pump schemes for plasma-induced harmonics [58,59], observation of extremely strong HHG in carbon-contained plasmas [39,40], proposals for the quasi-phase matching in plasma plumes [60], observation of the attosecond nature of pulse duration of the plasma-induced harmonics [61], etc. Most of these findings will be discussed in the present review.…”

Ion flux enhancements and oscillations in spatially confined laser produced aluminum plasmas

“…21 Recently, they were used in place of rare gas targets for the production of intense, monochromatic, EUV light using High Harmonic Generation (HHG). [22][23][24][25][26] Expansion of the plasma plume as well as its shape depend on the pressure gradient normal and parallel to the target surface. 27 Plasma properties are found to be highly dependent on the background gas which confines its expansion in the normal and tangential directions.…”

Generation of harmonics of laser radiation in plasmas

“…Recent findings of the physical processes driving plasma HHG require systematic analysis of the results reported after previous reviews of this process [33][34][35][36][37]. Those include the harmonic generation in clusters using ablation of commercially available clusters [38,39], fullerenes [40][41][42][43][44][45], and carbon nanotubes [46], enhancement of harmonics from in-situ-produced nanoparticles [47], new resonance-enhanced features of plasma harmonics [48,49], application of high pulse repetition rate sources and ultrashort pulses for the HHG in plasma plumes [21], proposals for the quasi-phase matching of harmonics in plasmas [50], observation of quantum path signatures in harmonic spectra from various ablated targets [22], achievement of µJ level of harmonic energies [28,29], development of few theoretical approaches describing the observed peculiarities of resonance enhancement and fullerene-induced harmonics [43,45,49,[51][52][53][54][55][56][57], observation of extremely broadened high-order harmonics [58], emergence of a "second" plateau in harmonic distribution [59], destructive interference of harmonics in the mixtures of different harmonic emitters inside the plasma [60], measurements of plasma harmonic's pulse duration in the attosecond time scale [32], etc.…”