KEYWORDS: Crystals, Laser crystals, High power lasers, Pulsed laser operation, Laser systems engineering, Laser energy, Laser induced damage, Frequency conversion, Crystal optics, Fusion energy
In high power laser system, the 3ω laser fluence can up to 6J/cm2 with triple frequency conversion efficiency up to 75%. Two high fluence laser experiments have been done for proving high efficiency output and damage resistance of KDP crystal. The KDP crystals have different performance in these two experiments due to their characteristics nuances. For the third harmonic crystal in first experiments, centimeter damage occurred on this crystal after about 50 number laser shots, and more than ten thousands micrometer damage points occurred on this crystal. For the second KDP crystal after about 60 number laser shots, most damage size are micrometer, including bulk damage and damage on back surface, micrometer damage doesn’t exist because of its good quality. We classify these damages of crystals to different kinds, observe characteristics of these damages. Observation of laser damage on third-harmonic converter crystals have been done in this paper.
Laser-induced damage is still the key issue to restrict the development of high power laser system for inertial confinement fusion (ICF). Based on a high power laser prototype, laser-induced damage behaviors and performance of large aperture final optics were experimentally studied. And, the damage inducement and morphology were comprehensively analyzed. Probability density functions (PDF) for laser fluence of near field with different resolution were obtained to analyze the influence of optical field distribution on the optical damage. High fluence of the near field was revealed in PDF with higher resolution, and the missing strong modulation fractions in the measured near field was most probably damage the optical elements. The surface damage morphology was observed and the main damage mechanism was discussed. Several kinds of surface damage morphologies with individual characteristics were sorted. The ratio of width and depth and the main contributors of laser damage were discussed.
Laser damage performance of large aperture optical components has been study under fourth harmonic of 1053nm Nd:glass laser irradiation (263nm).The threshold of optical components is very low under 263nm laser irradiation ,due to conversion of beam to higher energy photons of the quadrupled frequency (4ω), and is relative to material characteristic. A preliminary test of laser induced damage in fused silica (SiO2) and CaF2under 263nm laser is reported in this article. Thresholds of these two materials are obtained. Laser damage threshold of SiO2 is found about 2 J/cm2 by 1-on-1 method using pulsed 263nm laser, lower than CaF2 whose threshold.
KEYWORDS: Sensors, Photodetectors, Silicon, Superposition, Interference (communication), Data acquisition, Environmental sensing, Temperature metrology, Prisms, Signal to noise ratio
To accurately measure the linearity of photodetectors in near-infrared waveband, based on the beam superposition method, a new design idea which use the tow-beam path and correlation methods was proposed. Using the 1053nm laser, and the Si photodetector as the experimental subject, a linearity measurement system of highly accurate photodetectors was designed. This system has over seven orders of magnitude dynamic range. The joint uncertainty is superior to 0.08%. Meanwhile, the linear factor of four different conditions which include the different size of incident beam spots, incident angles, positions and the environment temperature have been measured and analyzed. The experiment shows that the linearity of Si photodetector is ideal when the size of beam spots are bigger, the incident angles are smaller and the environment temperature is lower, moreover, the linearity of margin area is unsatisfactory.
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