Tight focusing and blue shifting of millijoule femtosecond pulses from a conical axicon amplifier

Wood, W. M.; Focht, Glenn; Downer, M. C.

doi:10.1364/ol.13.000984

Cited by 83 publications

(16 citation statements)

References 19 publications

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“…(1). Because of the now reduced contrast between the guided and unguided portions of the pulse, the weak, ionization blueshifted photons [22] at the very front of the pulse are now visible.…”

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confidence: 99%

Self-Guiding of Ultrashort, Relativistically Intense Laser Pulses through Underdense Plasmas in the Blowout Regime

et al. 2009

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The self-guiding of relativistically intense but ultrashort laser pulses has been experimentally investigated as a function of laser power, plasma density, and plasma length in the blowout regime. The extent of self-guiding, observed by imaging the plasma exit, is shown to be limited by nonlinear pump depletion with observed self-guiding of over tens of Rayleigh lengths. Spectrally resolved images of the plasma exit show evidence consistent with self-guiding in the plasma wake. Minimal losses of the self-guided pulse resulted when the initial spot size was matched to the blowout radius.

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confidence: 99%

Self-Guiding of Ultrashort, Relativistically Intense Laser Pulses through Underdense Plasmas in the Blowout Regime

et al. 2009

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“…Polycrystalline Fe and Al targets were illuminated by 0.62 mm dye laser pulses with peak focused intensity I # 10 15 W͞cm 2 . Although our system could produce shorter, more intense pulses [18], optimum peak-to-pedestal contrast (10 5 at 60.9 ps and 10 3 at 60.23 ps)-and minimum target surface preexpansion-was achieved with the system operating at 120 fs and I # 10 15 W͞cm 2 [19]. I (and thus x osc ) was calibrated by standard pulse energy and spot size measurements and cross-checked by immersing the target surface in ϳ1 atm He gas, which caused a sharp reflectivity drop and breakdown spark when I $ I thresh 1.2 6 0.1 3 10 15 W͞cm 2 , the ionization threshold of He [20].…”

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Experimental Identification of “Vacuum Heating” at Femtosecond-Laser-Irradiated Metal Surfaces

et al. 1999

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Aluminum and iron targets were irradiated by intense (I # 10 15 W͞cm 2 ), 120 fs laser pulses with sufficiently high contrast such that the surface expanded no more than the peak electron quiver amplitude during excitation. Under these experimentally verified conditions, obliquely incident, p-polarized pulses uniquely experienced anomalous absorption, proportional to ͑Il 2 ͒ 0.64 , and as high as 20%. This extra absorption was distinguished from competing pump-induced linear mechanisms by fs-time-resolved reflectivity, and agreed quantitatively with essential features of Brunel's "vacuum heating," in which light is absorbed by drawing electrons into the vacuum and sending them back into the plasma with approximately the quiver velocity. [S0031-9007 (99)09116-4] PACS numbers: 52.50.Jm, 78.20.Ci, 78.47. + p Amplified, high contrast femtosecond laser pulses [1] have opened a new regime of laser-solid interactions in which intense light is deposited into a solid faster than the target surface can hydrodynamically expand [2]. While numerous experiments have used a single pulse to both excite and probe such sharply bound solid density fluids [3], they have not individually identified the many competing collisional and collisionless absorption mechanisms unique to this regime which an extensive theoretical literature [4-10] has enumerated. For example, Brunel [4] proposed over ten years ago that a moderately intense, p-polarized light pulse incident obliquely on an atomically abrupt metal surface could be strongly absorbed by pulling electrons into the vacuum during an optical cycle, then returning them to the surface with approximately the quiver velocity. Later simulations [5] predicted that, with a slight surface expansion of scale length L ϵ ͑≠ lnn e ͞≠z͒ 21 , the optical field would pull more electrons into the vacuum, and thus be even more strongly absorbed, as long as L did not significantly exceed the electron quiver amplitude x osc eE͞mv 2 . While this "vacuum heating" (VH) mechanism has been incorporated into laser-plasma codes [6], and may influence surface x-ray [11] and high harmonic [12] generation, and intense laser interaction with nanoclusters [13] and hollow capillaries [14]-and although a microscopically similar mechanism underlies high harmonic generation and above-threshold ionization in gases [15]-quantitative experimental identification of VH at metal surfaces is completely lacking.Two important barriers to such identification have been the production and verification of Brunel's condition L & x osc , and distinction of VH from competing linear mechanisms [7] such as inverse bremsstrahlung (IB), anomalous skin effect (ASE) [8], sheath inverse bremsstrahlung (SIB) [9], sheath transit absorption (STA) [10], and resonance absorption (RA) [16]. For example, 120 fs pulsed excitation at l 0.62 mm and peak intensity I 10 15 W͞cm 2 heats Al targets to a peak electron temperature of kT e ϳ 100 eV [3,7], resulting in a collision frequency n ϳ 5 3 10 15 s 21 [7]. For L 0, IB dominates under these conditions...

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“…Wilks et al [2] have also deduced an interesting additional consequence; the appearance of a time independent residual magnetic field with the characteristic wavelength equal to the vacuum wavelength of the passing radiation. Recent theory and experiment have conclusively demonstrated that a powerful short laser pulse propagating in a gas can experience a strong frequency blueshift caused entirely by the plasma generated by the pulse itself [4].…”

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confidence: 99%

Frequency up-conversion and trapping of ultrashort laser pulses in semiconductor plasmas

1999

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Tight focusing and blue shifting of millijoule femtosecond pulses from a conical axicon amplifier

Cited by 83 publications

References 19 publications

Self-Guiding of Ultrashort, Relativistically Intense Laser Pulses through Underdense Plasmas in the Blowout Regime

Self-Guiding of Ultrashort, Relativistically Intense Laser Pulses through Underdense Plasmas in the Blowout Regime

Experimental Identification of “Vacuum Heating” at Femtosecond-Laser-Irradiated Metal Surfaces

Frequency up-conversion and trapping of ultrashort laser pulses in semiconductor plasmas

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