Exact electrodynamics versus standard optics for a slab of cold dense gas

Abstract

We study light propagation through a slab of cold gas using both the standard electrodynamics of polarizable media and massive atom-by-atom simulations of the electrodynamics. The main finding is that the predictions from the two methods may differ qualitatively when the density of the atomic sample ρ and the wave number of resonant light k satisfy ρk −3 1. The reason is that the standard electrodynamics is a mean-field theory, whereas for sufficiently strong light-mediated dipole-dipole interactions the atomic sample becomes strongly correlated. The deviations from mean-field theory appear to scale with the parameter ρk −3 , and we demonstrate noticeable effects already at ρk −3 10 −2 . In dilute gases and in gases with an added inhomogeneous broadening the simulations show shifts of the resonance lines in qualitative agreement with the predicted Lorentz-Lorenz shift and "cooperative Lamb shift," but the quantitative agreement is unsatisfactory. Our interpretation is that the microscopic basis for the local-field corrections in electrodynamics is not fully understood.

Coupling Thermal Atomic Vapor to Slot Waveguides

“…The role of resonant dipole-dipole interactions between atoms is a topic of current debate [52,53], which indicates the need for improvements of the existing theories. An indepth understanding of this subject is not only relevant for a microscopic description of fundamental phenomena, such as light propagation in a medium, but also for atom-based applications like atomic clocks [54].…”

Strongly coupled cold atoms in bilayer dense lattices

“…) within the sample are generated deterministically such that light-mediated correlations are not initially built in the sample. Therefore, our simulation with fixed atomic positions differs from stochastic coupled-dipole numerical simulations [14,15,18,22,29] with random atomic positions. We assume that atoms in the lattice sites are in a steady-state and do not tunnel into the other sites, leading to the dipole moments of the atoms…”

“…Detailed derivations have been given in our previous works [16,22] and in the other groupʼs study [30] for different purposes. Equation (16) is obtained in the limit of large lateral size of the 2D planar lattice so that simulation result would be accurate for a sample with a large enough value of N a compared with a.…”

“…low-temperature) atoms with a sufficiently high number density due to potential applications in the areas of efficient light transport [2], quantum information processing [3], metamaterials [4], integrated optical devices [5], and nano-optics [6]. Recently realized experiments [7][8][9][10][11] for cold dense atoms motivate theoretical investigations [12][13][14][15][16][17][18][19][20][21][22][23][24] of light propagation at the microscopic level. Even if responses of a single two-level atom to the incident radiation have been fairly well known, optical behaviors of an aggregation of two-level atoms are far more elusive.…”

“…Light pressure and effects of photon recoils of the steady-state atoms are all neglected. Furthermore, low light intensity is considered so that the atomic lattices driven by the external light are well approximated as dipoles with fixed positions and described by the coupled-dipole equations [12][13][14][15][16][17]22]. We obtain local fields seen by dipoles at their positions by solving the coupled-dipole equations.…”