Tightly focused femtosecond laser pulse in air: from filamentation to breakdown

Liu, Xiaolong; Lü, Xingqiang; Liu, Xun; Xi, Tingting; Feng, Liqiang; Ma, Jing; Zhang, Jie

doi:10.1364/oe.18.026007

Cited by 75 publications

(52 citation statements)

References 25 publications

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“…Recently, we became aware of experimental results on filamentation in air with tight focusing conditions reporting intensities in the range 2-5 × 10 14 W/cm 2 and electron densities of 2.5 × 10 19 cm −3 , in agreement with the present results [40].…”

Section: Discussionsupporting

confidence: 92%

Focal dynamics of multiple filaments: Microscopic imaging and reconstruction

et al. 2010

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International audienceWe observe the complete dynamics of the propagation of very intense, femtosecond laser pulses in air under tight focusing conditions via direct imaging of the entire interaction zone. The whole life history of the focused pulses is then reconstructed by means of numerical simulations. We show that beam breakup leads to a dual-rate increase in filament numbers with laser power. Linearly and circularly polarized pulses give rise to beam breakup and fusion governed by external focusing conditions. For tight focusing conditions, intensity saturation due to plasma generation and nonlinear losses does not limit the intensity growth, thereby giving access to a new propagation regime featured by an efficient laser energy deposition in fully ionized air and intense 10^15 W/cm^2 pulses at the focus

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Section: Discussionsupporting

confidence: 92%

Focal dynamics of multiple filaments: Microscopic imaging and reconstruction

et al. 2010

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“…Initially the cavitation region in the center of the picture replicates the shape of the filament, and therefore the length of the filament can also be restored from the pictures; the errors of such rough estimates do not exceed the diameter of each cavitation bubble. The filament length has a logarithmic dependence on laser pulse energy ( figure 4(b)) similar to this, and can be found for various media in [29][30][31].…”

Section: Filament-induced Shock Wave Evolutionsupporting

confidence: 81%

Highly extended high density filaments in tight focusing geometry in water: from femtoseconds to microseconds

et al. 2015

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We report a new regime of filamentation in water in tight focusing geometry, very similar to the socalled superfilamentation seen in air. In this regime there is no observable conical emission and multiple small-scale filaments, but instead a single continuous plasma channel is formed. To achieve this specific regime the principal requirement is the usage of tight focusing and supercritical power of laser radiation. Together they guarantee extremely high intensity in the microvolume in water (∼10 14 W cm −2 ) and clamp the energy in the ultra-thin (approximately several microns) channel with a uniform plasma density distribution in it. Each point of the 'superfilament' becomes a center of spherical shock wave generation. The overlapped shock waves transform into one cylindrical shock wave. At low energies, a single spherical shock wave is generated from the laser beam waist, and its radius tends toward saturation as energy increases. At higher energies, a long stable contrast cylindrical shock wave is generated, whose length increases logarithmically with laser pulse energy. The linear absorption decreases the incoming energy delivered to the focal spot, which dramatically complicates the filament formation, especially in the case of loose focusing. Aberrations added to the optical scheme lead to multiple dotted plasma sources for shock wave formation, spaced along the axis of pulse propagation. Increasing the laser energy launches the filaments at each of the dots, whose overlapping leads to enhancing the length of the whole filament and therefore the shock impact on the material.

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“…However, we expect here that the length exceeds 2 mm (see Table 1), and we use another approach. As the intensity exceeds the optical breakdown threshold in air (≅10 14 W cm −2 [26]), an indirect way to evaluate the length of the high-intensity region is to image plasma formed in air. Using the beam at maximum energy (1.2 mJ), we produce plasma that is imaged thanks to its visible broadband light emission.…”

Section: Research Articlementioning

confidence: 99%

Millijoule femtosecond micro-Bessel beams for ultra-high aspect ratio machining

et al. 2015

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We report on a functional experimental design for Bessel beam generation capable of handling high-energy ultrashort pulses (up to 1.2 mJ per pulse of 50 fs duration). This allows us to deliver intensities exceeding the breakdown threshold for air or any dielectric along controlled micro-filaments with lengths exceeding 4 mm. It represents an unprecedented upscaling in comparison to recent femtosecond Bessel beam micromachining experiments. We produce void microchannels through glass substrates to demonstrate that aspect ratios exceeding 1200∶1 can be achieved by using single high-intensity pulses. This demonstration must lead to new methodologies for deep-drilling and high-speed cutting applications.

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Tightly focused femtosecond laser pulse in air: from filamentation to breakdown

Cited by 75 publications

References 25 publications

Focal dynamics of multiple filaments: Microscopic imaging and reconstruction

Focal dynamics of multiple filaments: Microscopic imaging and reconstruction

Highly extended high density filaments in tight focusing geometry in water: from femtoseconds to microseconds

Millijoule femtosecond micro-Bessel beams for ultra-high aspect ratio machining

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