Radiation forces and confinement of neutral particles into the pulse envelope. New regime of collision ionization

Kovachev, Lubomir M.

doi:10.1016/j.ijleo.2022.169943

Cited by 3 publications

(4 citation statements)

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“…To explain the phenomena of the conical emission accompanying the self-guided pulse during filamentation in gasses, several mechanisms and models under different circumstances have been proposed over the last three decades, such as Cherenkov emission and four-photon parametric mixing. − However, this phenomenon remains still not entirely understood and investigated. The following paragraph proposes a new physical mechanism that could explain the ionization with intensities below 10 12 W/cm 2 and some of the characteristics of the conical emission by a new type of collision ionization, as suggested in ref . Experimentally, it is observed that the conical change-over of the laser pulse profile, starting with a diameter of 0.8 mm at 20 cm from the source, drastically transforms into a colored spot (from deep UV to IR) with a size of approximately 20 cm at a 50 m distance, see Figure .…”

Section: Resultsmentioning

confidence: 99%

“… 5 − 7 However, this phenomenon remains still not entirely understood and investigated. The following paragraph proposes a new physical mechanism that could explain the ionization with intensities below 10 12 W/cm 2 and some of the characteristics of the conical emission by a new type of collision ionization, as suggested in ref ( 25 ). Experimentally, it is observed that the conical change-over of the laser pulse profile, starting with a diameter of 0.8 mm at 20 cm from the source, drastically transforms into a colored spot (from deep UV to IR) with a size of approximately 20 cm at a 50 m distance, see Figure 7 .…”

Section: Resultsmentioning

confidence: 99%

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Exceeding the Boundaries of the Paraxial Spatiotemporal Nonlinear Optics and Filamentation for Ultrashort Laser Pulses

et al. 2023

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An impressive phenomenon of observed plasma instability and conical emission under the propagation of ultrashort laser pulses in the air is reported. The discussed novel findings demonstrating nonlinear effects are incapable to be explained in the standard spatiotemporal paraxial optics. Three main mechanisms are investigated. The first one is related to the nonlinear nonparaxial mechanisms for waveguiding of femtosecond pulses, and the second one considers the mechanism of single filament formation at weak ionization. The third mechanism demonstrates a new physical effect leading to collision ionization with intensities in the range of 1010–1011 W/cm2. Furthermore, a new ionization regime of instability is suggested at intensities below the critical thresholds for multiphoton and tunnel ionization. The experimental results and findings are supported by theoretical analyses and numerical simulations.

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Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Exceeding the Boundaries of the Paraxial Spatiotemporal Nonlinear Optics and Filamentation for Ultrashort Laser Pulses

et al. 2023

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“…The ensuing collision ionization may be traced back to trapping by polarization forces of neutral particles into the pulse envelope. As the density of trapped particles grows gradually, and as it reaches a critical value, their collision with the free ones leads to ionization of the medium . The stable propagation of the laser pulse with a power in the range P cr < P pulse < 20 P cr and the observation of very weak ionization patterns into the pulse during this process, lead to the following basic questions: What kinds of equations are suitable to describe both diffraction and dispersion of broad-band (few and phase-modulated 20 – 40) femtosecond pulses?…”

Section: Introductionmentioning

confidence: 99%

“…As the density of trapped particles grows gradually, and as it reaches a critical value, their collision with the free ones leads to ionization of the medium. 11 The stable propagation of the laser pulse with a power in the range P cr < P pulse < 20 P cr and the observation of very weak ionization patterns into the pulse during this process, lead to the following basic questions: What kinds of equations are suitable to describe both diffraction and dispersion of broad-band (few and phase-modulated 20 – 40) femtosecond pulses? What kinds of nonlinear processes of narrow and broad-band pulses lead to asymmetrical spectrum broadening from the infrared spectral region to the visible one and the mechanism of filamentation?…”

Section: Introductionmentioning

confidence: 99%

Linear and Nonlinear Optics of Broad-Band Laser Pulses: Diffraction

Iordanova,

Miteva,

Dakova

et al. 2024

ACS Omega

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The typical spectrally limited laser pulse in the nearinfrared region is narrow-band up to 40−50 fs. Its spectral width Δk is much smaller than the carrying wavenumber k 0 (Δk ≪ k 0 ) . For such kinds of pulses, on distances of a few diffraction lengths, the diffraction is of a Fresnel's type and their evolution can be described correctly in the frame of the well-known paraxial evolution equation. The technology established in 1985 of amplification through chirping of laser pulses triggered remarkable progress in laser optics along with the construction of femtosecond (fs) laser facilities producing high intensity fields of the order of 10 15 −10 21 W/cm 2 . However, the duration of the pulse was quickly shortened from picoseconds down to 5−6 fs, which have a broadband nature (Δk ∼ k 0 ). The linear and nonlinear propagation dynamics of broad-band pulses is quite different form their narrowband counterparts. Here, we review the appropriate theoretical approach to study the evolution of the pulse. Moreover, we shed light on the different diffraction regimes inherent to both narrow-band and broad-band laser pulses and compare them to unveil the main differences. Using this very method, in subsequent papers, we will investigate the influence of the dispersion and nonlinearity on the laser pulse propagation in isotropic media.

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