Spectral and far-field broadening due to stimulated rotational Raman scattering driven by the Nike krypton fluoride laser

Weaver, James L.; Lehmberg, R. H.; Obenschain, S. P.; Kehne, D.; Wolford, M. F.

doi:10.1364/ao.56.008618

Cited by 34 publications

(17 citation statements)

References 35 publications

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“…3 for 50m of 200mbar Xe is comparable to that seen in Ref. [2] for beam propagation through a 100m air path.…”

Section: Numerical Resultssupporting

confidence: 85%

“…The simulation parameters are listed in Table 1 and correspond to the incident beam in Ref. [2]. Fig.…”

Section: Numerical Resultsmentioning

confidence: 99%

“…Nonetheless, it will suffice to model the field envelope as E 0 × G(t, x, y), see Ref. [2]. A measurement of the initial beam profile or the far field profile can be incorporated for more accurate results.…”

Section: B Spatial and Temporal Incoherencementioning

confidence: 99%

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Spectral broadening of a KrF laser via propagation through Xe in the negative nonlinear index regime

Epstein

Lehmberg²,

Sprangle

2019

Phys. Rev. A

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In inertial confinement (ICF) experiments at the NIKE [1] laser facility, the high-power krypton fluoride (KrF) laser output beams propagate through long (∼75m) air paths to achieve angular multiplexing, which is required because the KrF medium does not store energy for a sufficiently long time. Recent experiments and simulations have shown that, via stimulated rotational Raman scattering (SRRS), this propagation can spectrally broaden the laser beam well beyond the ∼1 THz laser linewidth normally achieved by the induced spatial incoherence (ISI) technique used in NIKE [2]. These enhanced bandwidths may be enough to suppress the laser-plasma instabilities which limit the maximum intensity that can be incident on the ICF target. In this paper we investigate an alternative technique that achieves spectral broadening by self-phase modulation in Xe gas, which has a large, negative nonlinear refractive index ∼ 248 nm [3], and thus completely avoids transverse filamentation issues. The collective, nonlinear atomic response to the chaotic, non-steady state ISI light is modeled using a two-photon vector model, and the effect of near-resonant behavior on the spectral broadening is studied.

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“…3 for 50m of 200mbar Xe is comparable to that seen in Ref. [2] for beam propagation through a 100m air path.…”

Section: Numerical Resultssupporting

confidence: 85%

“…The simulation parameters are listed in Table 1 and correspond to the incident beam in Ref. [2]. Fig.…”

Section: Numerical Resultsmentioning

confidence: 99%

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Spectral broadening of a KrF laser via propagation through Xe in the negative nonlinear index regime

Epstein

Lehmberg²,

Sprangle

2019

Phys. Rev. A

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“…As an alternative, recent experiments have successfully demonstrated that stimulated rotational Raman scattering can increase the bandwidth of high-energy lasers. 5 This summary presents a numerical study of absolute instability thresholds for SRS and TPD using a broadband pump beam. The calculations suggest that the absolute thresholds can be increased significantly with +1% bandwidth at ICF-relevant conditions.…”

mentioning

confidence: 99%

Thresholds of absolute instabilities driven by a broadband laser

et al. 2019

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Absolute instability thresholds for stimulated Raman scattering (SRS) and two-plasmon decay (TPD) driven by a broadband laser pulse are evaluated numerically. The scalings of the calculated thresholds with the density scale length, temperature, and central wavelength are qualitatively similar to the existing analytical results. The threshold values, however, exhibit significant quantitative differences. Comparisons between the thresholds calculated for various broadband power spectra indicate a universal scaling of the threshold intensity with laser coherence time (τc). For SRS, Ithr∝τc−1/3, and for TPD, Ithr∝τc−1/2.

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“…This effect has recently been observed in the ultraviolet region on the Nike kryptonfluoride (KrF) laser at the U.S. Naval Research Laboratory (NRL) [46] with only a modest degradation of the final focal distribution and may provide a practical approach for bandwidth enhancement on other, existing, direct-drive laser facilities [36,40].…”

mentioning

confidence: 99%

Mitigation of cross-beam energy transfer in inertial-confinement-fusion plasmas with enhanced laser bandwidth

et al. 2018

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Cross-beam energy transfer (CBET) is a significant energy-loss mechanism in directly driven inertial-confinement-fusion (ICF) targets. One strategy for mitigating CBET is to increase the bandwidth of the laser light, thereby disrupting the resonant three-wave interactions that underlie this nonlinear scattering process. Here, we report on numerical simulations performed with the wave-based code lpse that show a significant reduction in CBET for bandwidths of 2-5 THz (corresponding to a normalized bandwidth of 0.2%-0.6% at a laser wavelength of 351nm) under realistic plasma conditions. Such bandwidths are beyond those available with current high-energy lasers used for ICF, but could be achieved using stimulated rotation Raman scattering in diatomic gases like nitrogen.

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Spectral and far-field broadening due to stimulated rotational Raman scattering driven by the Nike krypton fluoride laser

Cited by 34 publications

References 35 publications

Spectral broadening of a KrF laser via propagation through Xe in the negative nonlinear index regime

Spectral broadening of a KrF laser via propagation through Xe in the negative nonlinear index regime

Thresholds of absolute instabilities driven by a broadband laser

Mitigation of cross-beam energy transfer in inertial-confinement-fusion plasmas with enhanced laser bandwidth

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