Random phase plates for beam smoothing on the Nova laser

Dixit, S. N.; Thomas, Ian M.; Woods, Bruce W.; Morgan, Amber J.; Henesian, Mark A.; Wegner, Paul J.; Powell, H. T.

doi:10.1364/ao.32.002543

Cited by 107 publications

(39 citation statements)

References 9 publications

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“…Two continuous phase plates [17] have been used for these studies to allow the intensity in these studies to range over several orders of magnitude. The high intensity phase plate has a vacuum focus diameter of 100 µm FWHM and provides an average intensity at best focus I 100 µm = E[J]×10 13 , where E is the incident laser-beam energy ranging from 100 to 400 J.…”

Section: B Interaction Beammentioning

confidence: 99%

Experimental basis for laser-plasma interactions in ignition hohlraums at the National Ignition Facility

et al. 2010

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A series of laser plasma interaction experiments at OMEGA (LLE, Rochester) using gas-filled hohlraums shed light on the behavior of stimulated Raman scattering and stimulated Brillouin scattering at various plasma conditions encountered in indirect drive ignition designs. We present detailed experimental results that quantify the density, temperature, and intensity thresholds for both of these instabilities. In addition to controlling plasma parameters, the National Ignition Campaign relies on optical beam smoothing techniques to mitigate backscatter. We show that polarization smoothing is effective at controlling backscatter. These results provide an experimental basis for forthcoming experiments on National Ignition Facility.

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Section: B Interaction Beammentioning

confidence: 99%

Experimental basis for laser-plasma interactions in ignition hohlraums at the National Ignition Facility

et al. 2010

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“…CPPs function in combination with a focusing element to define the size and shape of the beam at focus, the wavefront characteristics (uniformity) at the focal plane, and the intensity of the beam within the focal spot. To eliminate wavefront discontinuities or high contrast inherent in previous discrete (stepped) [4][5][6][7] plate designs, CPPs are made by imprinting a continuously varying phase profile onto an optical surface, Figure 1. This near-field topography is the key to enabling detailed control of the laser beam characteristics at the focal plane at high-power.…”

Section: Functionality Of Cpps In High-power Lasersmentioning

confidence: 99%

“…Lower efficiency forerunners of the CPP employed a resist masking and acid etching approach to imprint binary 4,5 (rectangular/hexagonal phase plate structure) and 16 level step patterns 6,7 (kinoform phase plate) onto fused silica surfaces similar to that used in the fabrication of integrated circuit boards. This approach was replaced by masking and resistive ion etching techniques that were capable of imprinting higher efficiency CPP patterns onto optics for use at the Laboratory for Laser Energetics 8,9 and the Laser MegaJoule facility 10 .…”

Section: Introductionmentioning

confidence: 99%

MRF applications: on the road to making large-aperture ultraviolet laser resistant continuous phase plates for high-power lasers

et al. 2006

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Over the past two years we have developed MRF tools and procedures to manufacture large-aperture (430 X 430 mm) continuous phase plates (CPPs) that are capable of operating in the infrared portion (1053 nm) of high-power laser systems. This is accomplished by polishing prescribed patterns of continuously varying topographical features onto finished plano optics using MRF imprinting techniques. We have been successful in making, testing, and using large-aperture CPPs whose topography possesses spatial periods as low as 4 mm and surface peak-to-valleys as high as 8.6 µm. Combining this application of MRF technology with advanced MRF finishing techniques that focus on ultraviolet laser damage resistance makes it potentially feasible to manufacture large-aperture CPPs that can operate in the ultraviolet (351 nm) without sustaining laser-induced damage. In this paper, we will discuss the CPP manufacturing process and the results of 351-nm/3-nsec equivalent laser performance experiments conducted on large-aperture CPPs manufactured using advanced MRF protocols.

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“…These techniques are called smoothing by spectral dispersion (SSD) [14][15] and polarization smoothing (PS) [16][17][18][19] was done by applying a 17 GHz oscillating RF field to an electro-optic crystal to modulate the phase of the seed laser pulse. The frequency-broadened pulse was dispersed with a diffraction grating, amplified by the Nova laser amplifiers, and then focused onto the target.…”

Section: A Nova Experimentsmentioning

confidence: 99%

Experimental investigation of short scalelength density fluctuations in laser-produced plasmas

et al. 2000

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The technique of near forward laser. scattering is used to infer characteristics of intrinsic and controlled density fluctuations in laser-produced plasmas. Intrinsic fluctuations are studied in long scalelength plasmas where the fluctuations exhibit scalesizes related to the size of the intensity variations in the plasma forming and interaction beams. Stimulated Brillouin forward scattering and filamentation appear to be the primary mechanism through which these fluctuations originate. The beam spray which results from these fluctuations is important to understand since it can affect symmetry in an inertial confinement fusion (ICF) experiment.Controlled fluctuations are studied in foam and exploding foil targets.Forward scattered light from foam targets shows evidence that the initial target inhomogeneities remain after the target is laser heated. Forward scattered light from an exploding foil plasma shows that a regular intensity pattern can be used to produce a spatially correllated density fluctuation pattern. These results provide data which can be used to benchmark numerical models of beam spray.

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Random phase plates for beam smoothing on the Nova laser

Cited by 107 publications

References 9 publications

Experimental basis for laser-plasma interactions in ignition hohlraums at the National Ignition Facility

Experimental basis for laser-plasma interactions in ignition hohlraums at the National Ignition Facility

MRF applications: on the road to making large-aperture ultraviolet laser resistant continuous phase plates for high-power lasers

Experimental investigation of short scalelength density fluctuations in laser-produced plasmas

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