Design of a production process to enhance optical performance of 3ω optics

Prasad, R.R.; Bruere, Justin R.; Halpin, John M.; Lucero, Phil; Mills, Steven; Bernacil, Michael; Hackel, Richard P.

doi:10.1117/12.523857

Cited by 13 publications

(6 citation statements)

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“…Management of this surface damage primarily involves controlling the exponential growth these sites will exhibit upon continued illumination [3]. One attractive technique to control or mitigate exponential growth of surface damage sites is via treatment with a CO 2 laser [4][5][6][7][8]. LLNL is currently pursuing two CO 2 laser-based mitigation approaches, evaporative and non-evaporative.…”

Section: Introductionmentioning

confidence: 99%

Results of applying a non-evaporative mitigation technique to laser-initiated surface damage on fused-silica

et al. 2010

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We present results from a study to determine an acceptable CO 2 laser-based non-evaporative mitigation protocol for use on surface damage sites in fused-silica optics. A promising protocol is identified and evaluated on a set of surface damage sites created under ICF-type laser conditions. Mitigation protocol acceptability criteria for damage re-initiation and growth, downstream intensification, and residual stress are discussed. In previous work [1], we found that a power ramp at the end of the protocol effectively minimizes the residual stress (<25 MPa) left in the substrate. However, the biggest difficulty in determining an acceptable protocol was balancing between low re-initiation and problematic downstream intensification. Typical growing surface damage sites mitigated with a candidate CO 2 laser-based mitigation protocol all survived 351 nm, 5 ns damage testing to fluences >12.5 J/cm 2 . The downstream intensification arising from the mitigated sites is evaluated, and all but one of the sites has 100% passing downstream damage expectation values. We demonstrate, for the first time, a successful non-evaporative 10.6 m CO 2 laser mitigation protocol applicable to fused-silica optics used on fusion-class lasers like the National Ignition Facility (NIF).

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Section: Introductionmentioning

confidence: 99%

Results of applying a non-evaporative mitigation technique to laser-initiated surface damage on fused-silica

et al. 2010

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“…However, such an operation is currently impractical given the high-grade finish that accompanies a new optic, and alternatives involving some acceptable modification of the damaged region must be pursued. Recently, CO 2 laser damage mitigation has been shown to repair and arrest the growth of damage sites created from 351nm pulses [1][2][3][4]. Because the region of the optical surface that was once damaged then becomes transformed into a region different from the original pristine material, limits must be placed on this transformation in terms of laser operation.…”

Section: Introductionmentioning

confidence: 99%

“…The operation of large aperture, high fluence laser systems such as the National Ignition Facility, depend on an effective remanufacturing or 'recycling' strategy to maximize the lifetime of high cost optics prone to damage [1][2][3][4]. In particular, the fused silica optics used as focusing elements are generally quite thick (~4cm), and must be produced from high-quality, inclusion-free SiO 2 , making these elements relatively expensive and of highest interest in terms of damage repair and recycling.…”

Section: Introductionmentioning

confidence: 99%

Downstream intensification effects associated with CO 2 laser mitigation of fused silica

et al. 2007

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Mitigation of 351nm laser-induced damage sites on fused silica exit surfaces by selective CO 2 treatment has been shown to effectively arrest the exponential growth responsible for limiting the lifetime of optics in high-fluence laser systems. However, the perturbation to the optical surface profile following the mitigation process introduces phase contrast to the beam, causing some amount of downstream intensification with the potential to damage downstream optics. Control of the laser treatment process and measurement of the associated phase modulation is essential to preventing downstream 'fratricide' in damage-mitigated optical systems. In this work we present measurements of the surface morphology, intensification patterns and damage associated with various CO 2 mitigation treatments on fused silica surfaces. Specifically, two components of intensification pattern, one on-axis and another off-axis can lead to damage of downstream optics and are related to rims around the ablation pit left from the mitigation process. It is shown that control of the rim structure around the edge of typical mitigation sites is crucial in preventing damage to downstream optics.

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“…It is clear that the three filters transmit almost an equal amount of light at around 810-850 nm. Thus 810 nm diodes were selected as the illumination source [1]. This imaging system acquires an image of the 43 cm x 43 cm optic and stores it as a 16-bit TIFF image in less than 1 minute.…”

Section: Optic Mountingmentioning

confidence: 99%

Design of an illumination technique to improve the identification of surface flaws on optics

et al. 2005

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An edge illumination technique has been designed using a monochromatic light source that improves the identification of surface flaws on optics. The system uses a high-resolution CCD camera to capture images of the optics. Conventional edge illumination methods using white light sources have been plagued by light leaking around the optics causing high background levels. The background combined with lower resolution cameras has made it difficult to determine size and intensity characteristics of the flaws. Thus photographs taken of the optics are difficult to analyze quantitatively and do not allow for the detection of small, faintly illuminated sites.Infrared diodes have been utilized to illuminate large-scale (43 cm x 43 cm) fused silica optics, and a two-dimensional array CCD camera has been used to collect the image data. Flaw sizes as small as ~10 µm have been detected. A set of frames has been built to support the infrared sources where one diode array per side is magnetically attached to the frame. The diodes inject light into the optic causing the sites to illuminate, which can be detected by the camera. A customized mounting design has been implemented to secure the frames to the stage, or base, for image acquisition. The design uses a dual bracket assembly to support the frames. With this design for optical illumination, quantitative data has been obtained of the surface flaws.A comparison of the peak intensity, total integrated intensity and size of the flaws measured in these images and the size of the flaws as measured using a microscope will be presented.

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Design of a production process to enhance optical performance of 3ω optics

Cited by 13 publications

References 0 publications

Results of applying a non-evaporative mitigation technique to laser-initiated surface damage on fused-silica

Results of applying a non-evaporative mitigation technique to laser-initiated surface damage on fused-silica

Downstream intensification effects associated with CO 2 laser mitigation of fused silica

Design of an illumination technique to improve the identification of surface flaws on optics

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