Preparation of one-dimensional chains and dense cold atomic clouds with a high numerical aperture four-lens system

We report the efficient and fast (∼2Hz) preparation of randomly loaded one-dimensional (1D) chains of individual Rb87 atoms and of dense atomic clouds trapped in optical tweezers using an upgraded experimental platform. This platform is designed for the study of atomic ensembles featuring either ordered or disordered distributions of the atomic positions. It is composed of two high-resolution optical systems perpendicular to each other, enhancing observation and manipulation capabilities. The setup includes a dynamically controllable telescope, which we use to vary the tweezer beam waist. A Λ-enhanced gray molasses on the D1 line enhances the loading of the traps from a magneto-optical trap. Using these tools, we prepare chains of up to ∼100 atoms separated by ∼1μm by retroreflecting the tweezer light, hence producing a 1D optical lattice with strong transverse confinement. Dense atomic clouds with peak densities up to n0∼1015 atoms/cm3 are obtained by compression of an initial cloud. This high density results in interatomic distances smaller than λ/(2π) for the D2 optical transitions, making it ideal to study light-induced interactions in dense samples.