Optical-optical double resonance spectroscopy of Rb 5D3/2,5/2 in magnetic fields

We have investigated the optical-optical double resonance (OODR) spectroscopy of 87Rb for transition 5S1/2 → 5P3/2 → 5D3/2,5/2 in magnetic fields. Unlike the electromagnetically induced transparency (EIT) spectroscopy of the transition to high Rydberg states (Opt Express, 25(2017)33575), the spectral observation to this low excited state remains much discrepancy compared to the theory simulation as the strong coupling between 5P3/2 and 5D3/2,5/2 leads to a state-dependent spectral broadening due to double resonance optical pumping (DROP) effect. Instead, the OODR method employs a weak optical coupling between these two states, serving as probe, where the spectral broadening can be ignored. We experimentally record the Zeeman-splitting spectrum of 87Rb to 5D3/2 and 5D5/2 in magnetic fields by OODR and the observed spectra are well in accordance with the theoretical calculation. It shows OODR is more suitable to investigate the high resolution spectroscopy of the excited state when the relaxation in DROP can't be neglected. [Display omitted] •We have found the complex state-dependent double resonance optical pumping (DROP) induced spectral broadening in Zeeman spectrum of Rb atom from the ground state 5S1/2 via the intermediate state 5P3/2 then to the excited state 5D3/2,5/2, which makes the spectrum difficult to explain for the strong coupling between the two upper states.•An optical-optical double resonance (OODR) spectroscopic method is employed to remove or reduce this spectral broadening by weak optical coupling between the upper two states 5P3/2 and 5D3/2,5/2 instead.•The Zeeman spectrum by OODR can be well explained by the theoretical calculation, which proves that the OODR method is more suitable to investigate the high resolution spectroscopy of the excited state when the state-dependent spectral broadening in double resonance optical pumping can't be neglected.