2025/11/20 by Jia Zhang, Zhang, Jia, Xiaolei Guan Ruihang Chen +5
Physics and Astronomy · #Advanced Frequency and Time Standards #Atomic Physics (physics.atom-ph) #Cold Atom Physics and Bose-Einstein Condensates #FOS: Physical sciences #Optical properties and cooling technologies in crystalline materials
paper · pdf · doi:10.48550/arxiv.2511.16220
openalex publication_date 2025/11/20 · openalex created_date 2025/11/23 · openalex updated_date 2026/07/28
To date, the laser cooling of rubidium atoms has inevitably relied on 780 nm cooling light corresponding to the first excited state 5P3/2. Surprisingly, we demonstrate laser cooling directly utilizing 420 nm blue light for active optical clock, which corresponds to the high excited state 6P3/2 of Rb atom. Experimentally, we successfully apply the 420 nm diffuse laser cooling technique to prepare a cold 87Rb atomic cloud with a length of up to one meter, and measure the cold-atom absorption spectroscopy. The cold atom number is approximately 4.4×107. We systematically compare the cooling effects of 420 nm and 780 nm diffuse laser cooling, and verify the feasibility of blue light cooling using high excited state. This work directly employs blue light to cool and manipulate ground-state Rb atoms to the 6P excited state, providing a new and efficient approach for the cold-atom active optical clock. It is also expected to open up research directions and application prospects in frontier fields such as Rydberg atoms, ultracold quantum gases Bose-Einstein condensation, quantum information, and so on.