{'fraction_non_alphanumeric': 0.02073365231259968, 'fraction_numerical': 0.003189792663476874, 'mean_word_length': 5.610526315789474, '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}}
“Two-Pass” Brillouin Scattering Geometry for the Investigation of Opto-Acoustic Properties of Thin Films

A new optical geometry for Brillouin scattering measurement of thin films is proposed. Making use of the two incident laser beams focused on the sample, simultaneous measurements of 90A scattering and back scattering were performed. The strong scattering peaks in the spectra enabled simultaneous measurements of hypersonic wave velocity and refractive index. Actually, the appearance of anisotropy in the polypropylene (PP) film was continuously observed as an increase of birefringence during the ultra-drawing process.