Spontaneous atomic crystallization via diffractive dephasing in optical cavities

Abstract

The design of an experiment on the spontaneous crystallization of a laser-cooled, but thermal atomic cloud into a hexagonally structured phase is discussed. Atomic interaction is mediated by the dipole potential of an optical lattice formed spontaneously in a multi-mode degenerate cavity from single-mode longitudinal pumping. The length scale of the structure is given by the diffractive dephasing between the spontaneous sidebands and the on-axis pump. A linear stability indicates that the transition can be observed in a cavity of moderate finesse compatible with having the cavity mirrors outside the vacuum cell. A new anti-reflection coated cell has been assembled for this purpose.

Self-Organization in Cold Atoms Mediated by Diffractive Coupling

“…This allows to control length scale and limit diffraction losses while keeping the modal properties of the plano-planar resonator. The calculations in [104] indicate that the relatively high losses introduced by the residual Fresnel reflection losses from the surface of four anti-reflected coated lenses might be just tolerable. Otherwise, one can use concentric or confocal configurations without intracavity lenses.…”

“…However, it is clear that the magnetic ordering poses much less stringent requirements on optical density than the electronic one. At Strathclyde, the apparatus was recently upgraded and it is planned to increase atom number by about a factor of 10 and the optical density by a factor of 2 [104].…”

“…For red detuning, both density and light intensity show hexagonally coordinated peaks, whereas for blue detuning the structures are complementary, i.e., honeycombs for the density and hexagonally coordinated peaks for the light intensity, as one might expect from the discussion of the single-mirror feedback system. The quantitative analysis in [52,104] indicates that threshold should be achievable in a cavity of only a moderate Finesse of 30 compatible with a cavity placed outside the vacuum chamber, if the anti-reflection coatings of the cell windows are of high quality. In [156], pumping with a vortex beam carrying orbital angular momentum is considered.…”

Self-Organization in Cold Atoms Mediated by Diffractive Coupling

“…honeycombs for the density and hexagonally coordinated peaks for the light intensity, as one might expect from the discussion of the single-mirror feedback system. The quantitative analysis in [52,104] indicates that threshold should be achievable in a cavity of only a moderate Finesse of 30 compatible with a cavity placed outside the vacuum chamber, if the anti-reflection coatings of the cell windows are of high quality. In [155] pumping with a vortex beam carrying orbital angular momentum is considered.…”