Modelling spectra of hot alkali vapour in the saturation regime

Häupl, Daniel R; Higgins, Clare R; Pizzey, Danielle; Briscoe, Jack D; Wrathmall, Steven A; Hughes, Ifan G; Löw, Robert; Joly, Nicolas Y

Abstract

Laser spectroscopy of hot atomic vapours has been studied extensively. Theoretical models that predict the absolute value of the electric susceptibility are crucial for optimising the design of photonic devices that use hot vapours, and for extracting parameters, such as external fields, when these devices are used as sensors. To date, most of the models developed have been restricted to the weak-probe regime. However, fulfilling the weak-probe power constraint may not always be easy, desired or necessary. Here we present a model for simulating the spectra of alkali-metal vapours for a variety of experimental parameters, most distinctly at intensities beyond weak laser fields. The model incorporates optical pumping effects and transit-time broadening. We test the performance of the model by performing spectroscopy of 87Rb in a magnetic field of 0.6 T, where isolated atomic resonances can be addressed. We find very good agreement between the model and data for three different beam diameters and a variation of intensity of over five orders of magnitude. The non-overlapping absorption lines allow us to differentiate the saturation behaviour of open and closed transitions. While our model was only experimentally verified for the D2 line of rubidium, the software is also capable of simulating spectra of rubidium, sodium, potassium and caesium over both D lines.

Citation

Häupl, D. R., Higgins, C. R., Pizzey, D., Briscoe, J. D., Wrathmall, S. A., Hughes, I. G., Löw, R., & Joly, N. Y. (2025). Modelling spectra of hot alkali vapour in the saturation regime. New Journal of Physics, 27, Article 033003. https://doi.org/10.1088/1367-2630/adb77c

• Journal Article Type: Article
• Acceptance Date: Feb 18, 2025
• Online Publication Date: Feb 28, 2025
• Publication Date: Mar 1, 2025
• Deposit Date: Mar 10, 2025
• Publicly Available Date: Mar 10, 2025
• Journal: New Journal of Physics
• Electronic ISSN: 1367-2630
• Publisher: IOP Publishing
• Peer Reviewed: Peer Reviewed
• Volume: 27
• Article Number: 033003
• DOI: https://doi.org/10.1088/1367-2630/adb77c
• Keywords: Paschen–Back, atomic transitions, computer model, Lindblad master equation, saturation intensity, atomic spectroscopy
• Public URL: https://durham-repository.worktribe.com/output/3560343