Abstract | A 633-nm He–Ne laser has been stabilized on a hyperfine component of an absorption line of natural iodine vapor by means of a servo system utilizing the zero crossing of the third harmonic of an applied modulation frequency. In its present form the laser has a 1000-sec stability of 1 × 10⁻¹¹ λ, and by virtue of the great reduction in background offset problems resulting from the third harmonic servo, a reproducibility without manual interference of 2 × 10⁻¹⁰ λ; improvement in both of these characteristics appears straightforward. The absolute wavelength measured against the Kr⁸⁶ standard is 632,991.398 ± 0.003 pm. |
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