Blue light emission of cold rubidium atoms via optical double resonance

Marcus Kienlen, Noah T. Holte, Hunter A. Dassonville +1 more

Marcus Kienlen

Arieh Grosman, Ilan Sher, Roy Zektzer +2 more

ABSTRACT Blue light emission from Rubidium (Rb) vapor cells is attractive for a myriad of applications, from quantum sensing and metrology to communication, quantum memories, and more. Typically, such emissions are observed from bulky free‐space glass cells. Here we experimentally demonstrate the generation of blue light from a chip‐scale optical waveguide integrated with rubidium vapor. The atomic ladder excitation using a combination of 780 and 776 nm light propagates through the Atomic Clad Waveguide (ACWG), directly interacting with Rubidium, emitting a photon at 420 nm and a matching photon at 5233 nm. The blue light emission is characterized and measured at elevated temperatures, up to 240°C. The results show a peculiar dependency of emission intensity as a function of temperature, wherein the emission intensity monotonically increases up to 200°C, followed by a pronounced roll‐off at higher temperatures. This is explained by a model that considers the reabsorption of emitted blue photons propagating along the optically thick Rubidium vapor. These results demonstrate a viable pathway for integrating nonlinear atomic vapor processes into chip‐scale quantum devices.

E Courtade, Marco Anderlini, D. Ciampini +5 more

By means of a simple theoretical model and experimental results, we analyse the two-photon ionization of cold rubidium atoms. We consider a two-step process in which ground state atoms are ionized by two blue (421 nm) photons, chosen to be quasi-resonant with the 5S → 6P transition. We show that for a good description of the process we have to take into account not only the three states coupled by the laser radiation, but also all the atomic states involved in the spontaneous emission cascade from the 6P to the 5S state, since optical pumping from 5S 1/2 ( F = 2) to the 5S 1/2 ( F = 1) states modifies the ionization efficiency when ionizing near resonance. The experimental and theoretical determination of ionization cross sections for excitations near resonance with the 6P 1/2 and the 6P 3/2 intermediate levels is presented.

A. Fioretti, Jérôme Lozeille, Carlo Andrea Massa +2 more

Pijush Kanti Mandal, Vaishali Naik, Vas Dev +2 more

In this work, we address the issue of the suitability of blue fluorescent light as a frequency offset reference during the ladder-level excitation 5S1/2→5P3/2→5D3/2 of Rb85 atoms. A simple pump–probe spectroscopy experiment is performed to generate non-degenerate blue light emission produced by the spontaneous decay route 5D3/2→6P3/2→5S1/2. By varying the relative intensity of the pump–probe combination, we can hover between regimes dominated by mechanisms such as double resonance optical pumping (DROP) and Autler–Townes splitting. The efficacy of the blue fluorescence (420 nm) as a frequency offset reference is pronounced under the DROP regime due to its narrow (∼natural) linewidth. To provide further insight into the stability performance, the pump laser connecting the 5P3/2→5D3/2 transition is stabilized to the peak of the blue light with the help of a probe stabilized to the saturation absorption signal of the 5S1/2→5P3/2 transition. For this purpose, we used the coherence-induced modulation transfer technique. The error frequency noise power spectra and the subsequent Allan variance calculation clearly show that probe fluctuations are transferred to the pump laser because of an existing two-photon coherent coupling.