Modulation transfer spectroscopy of the D1 transition of potassium: theory and experiment

• Published in: Journal of physics. B, Atomic, molecular, and optical physics Vol. 57; no. 7; pp. 75401 - 75410
• Main Authors: Innes, A D, Majumder, P, Noh, H R, Cornish, S L
• Format: Journal Article
• Language: English
• Published: IOP Publishing 12.04.2024
• Subjects: crossover; modulation transfer spectroscopy; potassium
• ISSN: 0953-4075; 1361-6455
• DOI: 10.1088/1361-6455/ad31af

Abstract We report on a study of modulation transfer spectroscopy of the 4 S 1 / 2 → 4 P 1 / 2 (D 1 ) transition of naturally abundant potassium in a room-temperature vapour cell. This transition is critical for laser cooling and optical pumping of potassium and our study is therefore motivated by the need for robust laser frequency stabilisation. Despite the absence of a closed transition, the small ground-state hyperfine splitting in potassium results in strong crossover features in the D 1 modulation transfer spectrum. To emphasise this we compare the D 1 and D 2 spectra of potassium with those of rubidium. Further, we compare our experimental results with a detailed theoretical simulation, examining different pump–probe polarisation configurations to identify the optimal signals for laser frequency stabilisation. We find good agreement between the experiment and the theory, especially for the lin ∥ lin polarisation configuration.