Transition from linear- to nonlinear-focusing regime of laser filament plasma dynamics

Reyes, Danielle; Baudelet, Matthieu; Richardson, Martin; Fairchild, Shermineh Rostami

doi:10.1063/1.5027573

Cited by 32 publications

(19 citation statements)

References 33 publications

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“…This measurement coincides with the onset of asymmetric spectral broadening. Note that the plasma feature is ~100 μm in diameter, as is expected based on previous measurements 10,34 . The initial generation of plasma was then combatted by a re-focusing event in the core region.…”

Section: Wavefront Dynamics Of Competing Nonlinearitiessupporting

confidence: 84%

“…The transition between the core and the reservoir is indicated by the fluence half width, which is ~200 μm at 0.95 m and indicated by the red lines. The reservoir extends radially from 200 μm to 0.5 mm and matches the expected size of the reservoir 5,10,36,47,[53][54][55] . Beyond 0.5 mm the positive wavefront curvature measured indicates that energy outside of the core-reservoir structure was directed away from the filament.…”

Section: Wavefront Dynamics Of Competing Nonlinearitiesmentioning

confidence: 57%

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Spatially resolved filament wavefront dynamics

Thul

Richardson

Fairchild

2020

Sci Rep

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Spatially resolved wavefront measurements are presented during nonlinear self-collapse and provide the first detailed characterization of wavefront evolution during filament formation. The wavefront dynamics of key nonlinear processes including Kerr self-focusing, ionization and plasma defocusing, and dynamic spatial replenishment are identified and resolved in both the filament core and reservoir regions. These results are analyzed and interpreted with respect to numerical simulations and provide insight into fundamental aspects of filamentation. They also inform applications based on phase manipulation, such as external beam guiding, and present a new method for measuring the nonlinear index of refraction, n 2. Filament formation is based on the nonlinear self-collapse of optical beams 1. Kerr self-focusing (KSF) enables this process by overcoming diffractive spreading when the peak-power of a beam exceeds the critical value for the propagation medium 2,3. This leads to increasing local intensities that surpass the ionization threshold of the medium 4. The presence of electrons decreases the local index of refraction, balancing KSF and resulting in an extended, highly confined plasma channel known as a filament 5. The unique nature of filaments has inspired both practical and academic interest in their capabilities. The properties of filaments have been well-characterized in several studies through measurements of the plasma channel density, lifetime, length, and diameter 6-10. The shape 11 , intensity 12 , spectral and temporal modifications 13-15 , and polarization 16 of the beam formed within the filament have also been studied in detail. The exploration of these properties has produced several novel filament-based applications including white-light seeded parametric amplification 17-19 , pulse compression 20,21 , white-light LIDAR 22,23 , sensing and spectroscopy 24-26 , cloud clearing 27,28 , material modification 29-31 , and guided discharges 32,33. The input (pre-collapse) wavefront of filament-forming beams has also been exploited to control filament properties after collapse, potentially aiding these applications. Altering the initial wavefront conditions allows the plasma density 34 , filament length 35 , spectral broadening 36 , and number of filaments 37-40 to be controlled. It also allows filaments to be organized as arrays, which is useful for nonlinear beam combination and external beam guiding 41-44. The filament-filament interactions within these arrays are of critical importance and are influenced by the transverse spatial structure of each filament's plasma, intensity, and wavefront profiles. However, the wavefront progression during collapse and within the filament itself has been largely ignored. Previous studies of the transverse filament wavefront profile have not measured the full collapse process or have lacked spatial resolution 45-47. The spatio-temporal nonlinear phase contributions within a filament have been previously been measured interferometrically, but these works do not inclu...

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Section: Wavefront Dynamics Of Competing Nonlinearitiessupporting

confidence: 84%

Section: Wavefront Dynamics Of Competing Nonlinearitiesmentioning

confidence: 57%

Spatially resolved filament wavefront dynamics

Thul

Richardson

Fairchild

2020

Sci Rep

Self Cite

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“…This is an essential starting point for any experiment or laboratory-scale simulation. When a pulse propagates in the linear regime, the intensity and plasma density will not be clamped and can reach values orders of magnitude higher than a filament achieves 19 . Geometric focusing of a USP will produce a tight focused spot, instead of a long plasma channel and high intensity pulse that propagates for many times the Rayleigh distance.…”

Section: Resultsmentioning

confidence: 99%

“…Balancing these nonlinear effects results in a plasma channel with clamped density and a pulse propagating with a clamped high intensity. At sea level, the intensity and plasma electron density are clamped to values of ~ 10 13 W/cm 2 and ~ 10 16 cm −3 , respectively 18 , 19 . The filament core profile has a characteristic Townesian shape, and a FWHM (full width at half maximum) diameter of 100 μm when generated by a pulse centered at 800 nm 20 , 21 .…”

Section: Introductionmentioning

confidence: 99%

“…Calculating the linear and nonlinear effects on the wavefront determines NA t , the transition NA at which nonlinear focusing effects dominate linear focusing 18 . In the linear regime, higher peak intensities and plasma densities can be accessed, but the tightly focused beam cannot propagate over long distances like a filament 19 . Typically, outdoor propagation will involve such a low NA that the nonlinear regime conditions will always be met.…”

Section: Introductionmentioning

confidence: 99%

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Filamentation in low pressure conditions

Pena

Reyes

Richardson

2022

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Filamentation is favorable for many long-range outdoor laser applications, some of which require propagation to or at high altitudes. Understanding how the filamentation process and filament properties are impacted by the low pressure conditions present at high altitudes is essential in designing effective applications. The scaling of filament preconditions with pressure is considered. An increase in critical power and decrease in transition numerical aperture (NA) is predicted to occur with a drop in pressure, indicating that nonlinear pulse propagation and filamentation at high altitudes requires higher energy and a longer assisted focal length than sea level filamentation. A summary of pressure-scaled filament properties is also presented. New simulations demonstrate filamentation at pressures as low as 0.0035 atm (38.5 km altitude) is possible.

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Focused beam self-cleaning during laser filamentation

et al. 2023

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The beam self-cleaning phenomenon is theoretically predicted by the two-dimensional nonlinear Schrödinger equation, which describes self-focusing, and is observed in the case of femtosecond laser filamentation in the collimated regime of propagation. However, the impact of external focusing on the self-cleaning has not been investigated so far. In this paper we systematically study this impact in a wide range of focusing conditions. We show that the energy range, in which self-cleaning can be observed, shrinks monotonically with the numerical aperture growth at some point vanishing at all.

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Transition from linear- to nonlinear-focusing regime of laser filament plasma dynamics

Cited by 32 publications

References 33 publications

Spatially resolved filament wavefront dynamics

Spatially resolved filament wavefront dynamics

Filamentation in low pressure conditions

Focused beam self-cleaning during laser filamentation

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