The existence of crossover resonances makes saturated-absorption (SA) spectra very complicated when external magnetic field B is applied. It is demonstrated for the first time, to the best of our knowledge, that the use of micrometric-thin cells (MTCs, L ≈ 40 μm) allows application of SA for quantitative studies of frequency splitting and shifts of the Rb atomic transitions in a wide range of external magnetic fields, from 0.2 up to 6 kG (20-600 mT). We compare the SA spectra obtained with the MTC with those obtained with other techniques and present applications for optical magnetometry with micrometer spatial resolution and a broadly tunable optical frequency lock.

By experimental exploration of the so-called λ-Zeeman technique based on Rb nano-cell use we reveal for the first time a strong modification of the probability of the 87 Rb, D2 line Fg = 1 → Fe = 0, 1, 2, 3 atomic transitions, including forbidden Fg = 1, mF = 0 → Fe = 1, mF = 0 and Fg = 1, mF = −1 → Fe = 3, mF = −1 transitions (these are forbidden transitions when B = 0) in a strong external magnetic field B in the range of 100 − 1100 G. For π-polarized exciting diode laser radiation (λ = 780 nm) these forbidden transitions at B > 150 G are among the strongest atomic transitions in the detected transmission spectra. Frequency shifts of the individual hyperfine transitions versus magnetic field are also presented: particularly, Fg = 1, mF = +1 → Fe = 1, mF = +1 atomic transition has a unique behavior, since its frequency remains practically unchanged when B varies from 100 to 1100 G. Developed theoretical model well describes the experiment.