Sub-wavelength structured optical potentials for cold atoms
We recently demonstrated conservative optical lattices with subwavelength spatial structure. (PRL 120 083601 (2018)) The potential is based on the nonlinear optical response of three-level atoms in laser-dressed dark states. Such non-linear response is not constrained by the diffraction limit of the light generating the potential. The lattice consists of a one-dimensional array of ultranarrow barriers with widths less than 10 nm, well below the wavelength of the lattice light, physically realizing a Kronig-Penney potential. The laser dressed dark states are surprisingly long-lived: even on resonance, the observed lifetimes of atoms trapped in the lattice are up to 44 ms, nearly 100,000 times the excited state lifetime. The lifetime could be further improved with more laser intensity. The potential is readily generalizable to higher dimensions and different geometries, allowing, for example, nearly perfect box traps, narrow tunnel junctions for atomtronics applications, and dynamically generated lattices with subwavelength spacings. See https://journals.aps.org/prl/abstract/10.1103/PhysRevLett.120.083601 (editor's pick), and here for APS Physics viewpoint news coverage.