{'fraction_non_alphanumeric': 0.019592476489028215, 'fraction_numerical': 0.006269592476489028, 'mean_word_length': 5.139423076923077, 'pattern_counts': {'":': 0, '<': 0, '<?xml version=': 0, '>': 0, 'https://': 0, 'lorem ipsum': 0, 'www.': 0, 'xml': 0}, 'pii_count': 0, 'substrings_counts': 0, 'word_list_counts': {'cursed_substrings.json': 0, 'profanity_word_list.json': 0, 'sexual_word_list.json': 0, 'zh_pornsignals.json': 0}}
Measurement In Visible Light Of Wavefront Errors Produced By Dielectric-Enhanced Infrared Reflectors: Some Calculations

Modern high energy laser mirrors require very high reflectances (greater than 99.9%) for operation. Simple metallic coatings cannot give a high enough reflectance, so further dielectric layers must be added to enhance the reflectance. Such mirrors may be several meters in diameter and strongly curved, making uniform coatings difficult to deposit. The reflectance is not critically dependent on the thicknesses of the layers, but a 1% thickness error for a typical 6-layer design gives a wavefront phase error of .01X. Worse, this error is a function of wavelength; the wavefronts may be very different in visible light than at the infrared design wave-length. Due to a nonlinear relation between coating thickness and the optical phase change on reflection, the wavefront in the visible may look very little like the coating thickness distribution that produces it. A technique for determining coating thickness distributions for an IR coating from interferograms taken at 2 or more visible wavelengths has been developed. The usefulness of the method has been studied by a series of calculations, and the means of obtaining good accuracy are described.