David N. Fittinghoff

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We use the algorithmic method of generalized projections (GP's) to retrieve the intensity and phase of an ultrashort laser pulse from the experimental trace in frequency-resolved optical gating (FROG). Using simulations, we show that the use of GP's improves significantly the convergence properties of the algorithm over the basic FROG algorithm. In(More)
We show that frequency-resolved optical gating combined with spectral interferometry yields an extremely sensitive and general method for temporal characterization of nearly arbitrarily weak ultrashort pulses even when the reference pulses is not transform limited. We experimentally demonstrate measurement of the full time-dependent intensity and phase of a(More)
Frequency-resolved optical gating (FROG), a technique for measuring ultrashort laser pulses, involves producing a spectrogram of the pulse and then retrieving the pulse intensity and phase with an iterative algorithm. We study how several types of noise — multiplicative, additive, and quantization — affect pulse retrieval. We define a convergence criterion(More)
We demonstrate what is to our knowledge the first frequency-resolved optical gating (FROG) technique to measure ultrashort pulses from an unamplified Ti:sapphire laser oscillator without direction-of-time ambiguity. This technique utilizes surface third-harmonic generation as the nonlinear-optical effect and, surprisingly, is the most sensitive third-order(More)
Ultrashort-laser-pulse retrieval in frequency-resolved optical gating has previously required an iterative algorithm. Here, however, we show that a computational neural network can directly and rapidly recover the intensity and phase of a pulse.
Hydrodynamic instabilities can cause capsule defects and other perturbations to grow and degrade implosion performance in ignition experiments at the National Ignition Facility (NIF). Here, we show the first experimental demonstration that a strong unsupported first shock in indirect drive implosions at the NIF reduces ablation front instability growth(More)
Experiments have recently been conducted at the National Ignition Facility utilizing inertial confinement fusion capsule ablators that are 175 and 165  μm in thickness, 10% and 15% thinner, respectively, than the nominal thickness capsule used throughout the high foot and most of the National Ignition Campaign. These three-shock, high-adiabat, high-foot(More)
We report on the first layered deuterium-tritium (DT) capsule implosions indirectly driven by a "high-foot" laser pulse that were fielded in depleted uranium hohlraums at the National Ignition Facility. Recently, high-foot implosions have demonstrated improved resistance to ablation-front Rayleigh-Taylor instability induced mixing of ablator material into(More)
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