Dynamic Polarizability of the 85Rb 5D3/2-State in 1064 nm Light

Abstract

We report a measurement of the dynamic (ac) scalar polarizability of the 5D3/2 state in 85Rb atoms at a laser wavelength of 1064 nm. Contrary to a recent measurement in Phys. Rev. A 104, 063304 (2021), the experiments are performed in a low-intensity regime in which the ac shift is less than the 5D3/2 state’s hyperfine structure, as utilized in numerous experiments with cold, trapped atoms. The extracted ac polarizability is α5D3/2=−499±59 a.u., within the uncertainty of the aforementioned previous result. The calibration of the 1064 nm light intensity, performed by analyzing light shifts of the D1 line, is the main source of uncertainty. Our results are useful for applications of the Rb 5D3/2 state in metrology, quantum sensing, and fundamental-physics research on Rydberg atoms and molecules.

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).…”

“…As mentioned in section 1, the 4D J states in Rb offer similar features as the 5D J states, which is attractive for compact atomic-clock designs. Moreover, our calculations [38,40] of the 4D 3/2 state's AC polarizability, α, shown in figure 6 together with α for the ground 5S 1/2 state, reveal two instances at which α for both states match at NIR wavelengths. One is at 1036.3 nm (for 4D 3/2 , m J = 3/2), another-at 1061.8 nm (for 4D 3/2 , m J = 1/2).…”

“…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.…”

“…The 1476 nm laser is locked at a fixed frequency to a temperature-stabilized Fabry-Pérot etalon, is kept always on, and is linearly polarized along the cavity axis. Since the laser beams entering the OL cavity are linearly polarized as well [40], the two-photon excitation has a lin. ⊥ lin.…”

“…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.…”