{'fraction_non_alphanumeric': 0.029, 'fraction_numerical': 0.035, 'mean_word_length': 4.381720430107527, 'pattern_counts': {'":': 0, '<': 1, '<?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}}
Comparison of two wavelength reference laser systems at λ ≈ 515 nm, stabilized by different methods

The results of a comparison of two of the BIPM iodine-stabilized Ar+ laser systems at λ ≈ 515 nm are presented. One of these laser systems uses the traditional third-harmonic locking technique while the other is realized using high-frequency modulation techniques. The frequency stability found in terms of the relative Allan standard deviation was 1,3 × 10-12 τ-1/2 for τ < 100 s, with a minimum of 1,5 × 10-13 at about 100 s. This limit is believed to be set by imperfections in the servo electronics for the laser using the third harmonic technique. The frequency difference between the two lasers was measured for the a3 component of the P(13) 43-0 transition over a period of twelve days. The mean frequency difference was found to be 0,1 kHz with a sample standard deviation of 1 kHz. The influence on the laser frequency of the modulation index, iodine pressure and laser power are discussed.