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 Rb-87 for transition 5S(1/2) -> 5P(3/2) -> 5D(3/2,5/2) 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 5P(3/2) and 5D(3/2),(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 Rb-87 to 5D(3/2) and 5D(5/2) 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.