ac polarizability and photoionization-cross-section measurements in an optical lattice

Spectroscopy of the 85Rb 4 D3/2 state for hyperfine-structure determination

“…Because the atomic sample is not magnetized, and because the MOT field near the MOT trapping region tends to be randomly oriented, when averaged over all atoms, the Zeeman shifts are symmetric and merely cause a line broadening of up to about 1 MHz, with no net line shift at our level of precision (∼100 kHz). It is noted that in previous work [38,40] on this setup there were also no observable effects from Zeeman shifts. At the highest 1476 nm power used, the strong and maximally AC-shifted |F = 3, m F = ±1⟩ → |F ′ ′ = 4, m F = 0⟩ line, which is less magnetic-field-broadened than most other magnetic sub-transitions, likely causes the relatively sharp feature at the very right of the spectrum in figure 2(a).…”

“…The main features of the setup's design and of the atom preparation method have been described in detail elsewhere [50]. In recent experiments performed with this setup [38,40], the atomic response to 1064 nm light has been the central subject of study. In the present measurements the role of the 1064 nm OL is limited to providing an atom column density that is high enough for the signal-to-noise ratio of the atomic absorption lines of interest to reach a level at which the measurements become practical.…”

“…As the upper-transition (1476 nm) laser is fixed in frequency, we scan the two-photon 5S 1/2 → 4D 3/2 transition by scanning the 795 nm laser via the frequency control afforded by the OPLL lock [38]. Hence, the intermediate-state detuning, ∆, defined to be 0 MHz at the field-free 5S 1/2 , F = 3 → 5P 1/2 , F ′ = 3 transition (see figure 1(b)), and the two-photon detuning of the 5S 1/2 → 4D 3/2 transition are scanned synchronously.…”

“…Notably, several proposals along these lines involve Rydberg-atom excitation in 1064 nm (or similar) laser traps. However, measurements on Rb 5D J states in 1064 nm dipole traps [37,38] have revealed large photo-ionization (PI) cross sections at this wavelength. Although PI of atoms laser-cooled and -trapped in a NIR-laser focus may be a convenient method to prepare a cold-ion source [39], PI presents an unwanted complication for the aforementioned Rydberg-physics applications, even at moderate 1064 nm laser power [38,40].…”

“…However, measurements on Rb 5D J states in 1064 nm dipole traps [37,38] have revealed large photo-ionization (PI) cross sections at this wavelength. Although PI of atoms laser-cooled and -trapped in a NIR-laser focus may be a convenient method to prepare a cold-ion source [39], PI presents an unwanted complication for the aforementioned Rydberg-physics applications, even at moderate 1064 nm laser power [38,40]. The Rb 4D J state, however, has an ionization wavelength of 698 nm, allowing the use of NIR laser traps in the above proposals without limitations due to PI.…”