7 February 2006 A system for measuring defect induced beam modulation on inertial confinement fusion-class laser optics
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A multi-wavelength laser based system has been constructed to measure defect induced beam modulation (diffraction) from ICF class laser optics. The Nd:YLF-based modulation measurement system (MMS) uses simple beam collimation and imaging to capture diffraction patterns from optical defects onto an 8-bit digital camera at 1053, 527 and 351 nm. The imaging system has a field of view of 4.5 x 2.8 mm2 and is capable of imaging any plane from 0 to 30 cm downstream from the defect. The system is calibrated using a 477 micron chromium dot on glass for which the downstream diffraction patterns were calculated numerically. Under nominal conditions the system can measure maximum peak modulations of approximately 7:1. An image division algorithm is used to calculate the peak modulation from the diffracted and empty field images after the baseline residual light background is subtracted from both. The peak modulation can then be plotted versus downstream position. The system includes a stage capable of holding optics up to 50 pounds with x and y translation of 40 cm and has been used to measure beam modulation due to solgel coating defects, surface digs on KDP crystals, lenslets in bulk fused silica and laser damage sites mitigated with CO2 lasers.
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Mike Runkel, Mike Runkel, Ruth Hawley-Fedder, Ruth Hawley-Fedder, Clay Widmayer, Clay Widmayer, Wade Williams, Wade Williams, Carolyn Weinzapfel, Carolyn Weinzapfel, Dave Roberts, Dave Roberts, } "A system for measuring defect induced beam modulation on inertial confinement fusion-class laser optics", Proc. SPIE 5991, Laser-Induced Damage in Optical Materials: 2005, 59912H (7 February 2006); doi: 10.1117/12.638824; https://doi.org/10.1117/12.638824

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