Self-Organization in Cold Atoms Mediated by Diffractive Coupling

Abstract

This article discusses self-organization in cold atoms via light-mediated interactions induced by feedback from a single retro-reflecting mirror. Diffractive dephasing between the pump beam and the spontaneous sidebands selects the lattice period. Spontaneous breaking of the rotational and translational symmetry occur in the 2D plane transverse to the pump. We elucidate how diffractive ripples couple sites on the self-induced atomic lattice. The nonlinear phase shift of the atomic cloud imprinted onto the optical beam is the parameter determining coupling strength. The interaction can be tailored to operate either on external degrees of freedom leading to atomic crystallization for thermal atoms and supersolids for a quantum degenerate gas, or on internal degrees of freedom like populations of the excited state or Zeeman sublevels. Using the light polarization degrees of freedom on the Poincaré sphere (helicity and polarization direction), specific irreducible tensor components of the atomic Zeeman states can be coupled leading to spontaneous magnetic ordering of states of dipolar and quadrupolar nature. The requirements for critical interaction strength are compared for the different situations. Connections and extensions to longitudinally pumped cavities, counterpropagating beam schemes and the CARL instability are discussed.

Atomic Compass: Detecting 3D Magnetic Field Alignment with Vector Vortex Light

“…In our experiment, we had to balance the low probe intensity required for the weak-coupling limit with the necessity for high contrast absorption images from our detectors. Therefore, although providing a concise insight, the perturbative regime required for equation (6) was not fully applicable to our conditions, and we may observe a spatial analogue of intensity broadening. A model based on the full optical Bloch equations, normalised to the data and fitting on the beam intensity, leads to excellent agreement.…”

“…Most investigations and applications of light-atom interaction are concerned with homogeneously polarized light, or scalar light. Light-atom interaction however, by its very nature, is a vectorial process, that depends explicitly on the alignment between an external magnetic field and the optical and atomic polarizations [1][2][3][4][5][6]. Over the last decades, the generation and use of vectorial light fields with spatially varying polarization profiles has matured into an active research area, with a plethora of applications in the optical domain [7][8][9][10][11], including communication [12], polarimetry [13] and super-resolution imaging [14].…”

Classical and Quantum Collective Recoil Lasing: A Tutorial

“…Optomechanics is now a large and highly active field of research which encompasses the interaction between light and matter (ranging from microscopic atoms to macroscopic membranes or moving mirrors), involving the mechanical effect of light on matter and the consequent backaction of the moving matter on the optical field. Optomechanical interactions have been used as the basis for new nonlinear optical phenomena (e.g., spontaneous self-structuring of cold gases and BEC [59]) and potential applications as ultrasensitive detectors of inertial forces or displacements [60,61].…”

Rotating and spiraling spatial dissipative solitons of light and cold atoms

“…Schemes involving cold atomic gases in longitudinally pumped cavities or single-mirror systems have been recently investigated theoretically and experimentally [7] and shown to achieve light-atom self-structuring where the relevant coupling involves optomechanical (dipole) forces [8][9][10][11], electronic [12,13], and magnetic transitions [14][15][16][17]. In particular, the collective nature of optomechanical self-structuring has provided insight into several aspects of cold and ultracold atom physics, such as collective atomic recoil lasing in ring cavities [18][19][20][21], crystallization [22][23][24], supersolidity with continuous symmetry breaking [25][26][27][28], photon-mediated interactions with tunable range [29], and structural transitions between crystalline configurations [30,31].…”