Ionization waves of arbitrary velocity driven by a flying focus

Palastro, J. P.; Turnbull, D.; Bahk, S.-W.; Follett, R. K.; Shaw, Jessica; Haberberger, D.; Bromage, J.; Froula, D. H.

doi:10.1103/physreva.97.033835

Cited by 55 publications

(35 citation statements)

References 31 publications

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“…The spot size in the right inset, where the full bandwidth is present, has increased at the same z position compared to the left inset since not all colors are in best focus with the LC present. This increase of time-integrated beam waist is a characteristic signature of LC in focus [11]. In contrast, it is important to emphasize that for a chirped beam, the instantaneous beam waist at the intensity peak of the beam is not increased compared to the case of the LC-free beam.…”

Section: Measurement Of the Flying Focusmentioning

confidence: 87%

“…The combination of the longitudinal separation of the frequencies in focus and a frequencyvarying arrival time, described by the group delay dispersion (GDD) φ 2 , produces the flying focus effect where within the extended focal region the intensity peak of the pulse can travel at velocities radically different from c [9][10][11]. This concept is shown schematically in Figs.…”

Section: Overview Of the Flying Focusmentioning

confidence: 99%

“…5(b)). This shorter local duration within the focal region, compared to the duration of the unfocused chirped pulse, is a key characteristic signature of the flying focus effect [9,11].…”

Section: Measurement Of the Flying Focusmentioning

confidence: 99%

“…Here we discuss the so-called flying focus effect whereby the velocity of the light intensity peak formed within the focal region of a broadband laser pulse can be arbitrarily different than the speed of light via very simple spatio-temporal shaping [9,10]. This recently identified effect has many potential scientific applications such as ionization waves of arbitrary velocity [11][12][13], Raman amplification in a plasma [14], particle acceleration [15], and photon acceleration [16]. The flying focus (also referred to as the "sliding focus") has been demonstrated on a laser system with sub-picosecond duration [10] using a diffractive lens to induce spatio-temporal couplings, a scheme well-suited to the rather narrow spectral width of such a laser.…”

Section: Introductionmentioning

confidence: 99%

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Controlling the velocity of a femtosecond laser pulse using refractive lenses

Jolly¹,

Gobert²,

Jeandet³

et al. 2020

Opt. Express

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The combination of temporal chirp with a simple chromatic aberration known as longitudinal chromatism leads to extensive control over the velocity of laser intensity in the focal region of an ultrashort laser beam. We present the first implementation of this effect on a femtosecond laser. We demonstrate that by using a specially designed and characterized lens doublet to induce longitudinal chromatism, this velocity control can be implemented independent of the parameters of the focusing optic, thus allowing for great flexibility in experimental applications. Finally, we explain and demonstrate how this spatiotemporal phenomenon evolves when imaging the ultrashort pulse focus with a magnification different from unity.

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Section: Measurement Of the Flying Focusmentioning

confidence: 87%

Section: Overview Of the Flying Focusmentioning

confidence: 99%

“…5(b)). This shorter local duration within the focal region, compared to the duration of the unfocused chirped pulse, is a key characteristic signature of the flying focus effect [9,11].…”

Section: Measurement Of the Flying Focusmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Controlling the velocity of a femtosecond laser pulse using refractive lenses

Jolly¹,

Gobert²,

Jeandet³

et al. 2020

Opt. Express

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“…The parameters correspond to a frequency-doubled Ti:sapphire laser propagating in hydrogen gas. The electron density profile used in the photon kinetics simulations was extracted from self-consistent simulations that capture the evolution of the drive pulse and the ionization dynamics of the medium in which it propagates [30]. Ultimately, the electron density profile is generated and modified by field ionization, collisional ionization, radiative recombination, and three-body recombination, while the temperature evolves through inverse Bremsstrahlung absorption and ionization cooling.…”

mentioning

confidence: 99%

Photon Acceleration in a Flying Focus

et al. 2019

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A high-intensity laser pulse propagating through a medium triggers an ionization front that can accelerate and frequency-upshift the photons of a second pulse. The maximum upshift is ultimately limited by the accelerated photons outpacing the ionization front or the ionizing pulse refracting from the plasma. Here we apply the flying focus-a moving focal point resulting from a chirped laser pulse focused by a chromatic lens-to overcome these limitations. Theory and simulations demonstrate that the ionization front produced by a flying focus can frequency-upshift an ultrashort optical pulse to the extreme ultraviolet over a centimeter of propagation. An analytic model of the upshift predicts that this scheme could be scaled to a novel table-top source of spatially coherent x-rays.A growing number of scientific fields rely critically on high intensity, high-repetition rate sources of extreme ultraviolet (XUV) radiation (wavelengths < 120 nm). These sources provide highresolution imaging for high energy density physics and nanotechnology [1,2], fine-scale material ablation for nanomachining, spectrometry, and photolithography [3][4][5], and ultrafast pump/probe techniques for fundamental studies in atomic and molecular physics [6][7][8]. While XUV sources have historically been challenging to produce, methods including nonlinear frequency mixing [9], high harmonic generation [10,11], and XUV lasing or line emission in metal-vapor and noble-gas plasmas [5,12] have demonstrated promising results. Despite their successes, each of these methods introduces tradeoffs in terms of tunability, spatial coherence, divergence, or efficiency [5,[9][10][11][12]. Photon acceleration offers an alternative method for tunable XUV production that could lessen or even eliminate these tradeoffs.Photon acceleration refers to the frequency upshift of light in response to a refractive index that decreases in time [13,14]. In analogy to charged particle acceleration, the increase in photon energy, i.e. frequency, accompanies an increase in group velocity. In the context of an electromagnetic pulse, the leading phase fronts experience a higher index than adjacent, trailing phase fronts, which manifests as a local phase velocity that increases over the duration of the pulse.The trailing phase front, on account of its higher phase velocity, gradually catches up with the

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