Shape-preserving diffusion of a high-order mode

Abstract

The close relation between the processes of paraxial diffraction and coherent diffusion is reflected in the similarity between their shape-preserving solutions, notably the Gaussian modes. Differences between these solutions enter only for high-order modes. Here we experimentally study the behavior of shape-preserving high-order modes of coherent diffusion, known as "elegant" modes, and contrast them with the nonshape-preserving evolution of the corresponding "standard" modes of optical diffraction. Diffusion of the light field is obtained by mapping it onto the atomic coherence field of a diffusing vapor in a storage-of-light setup. The growth of the elegant mode fits well the theoretical expectations.

How to measure diffusional decoherence in multimode rubidium vapor memories?

“…Typically diffusional motion of atoms in a buffer gas limits the storage time [13,14], restricts the number of spatial modes retrieved [11] or broadens the EIT spectrum [15]. Knowledge of the exact diffusion coefficient is particularly important for designing experiments with diffraction cancellation [12,[16][17][18]. Further progress would be significantly facilitated if one possessed convenient, robust and repeatable method for precise diagnostic of decoherence in the actual cell of a particular setup.…”

Direct observation of atomic diffusion in warm rubidium ensembles

“…In all of the above examples, the diffusion rate was among primary performance-limiting factors. Its importance has been recognized and its effect on EIT [8][9][10][11] and on the gradient echo memory [12][13][14] has been studied both experimentally and theoretically.…”

Shape-preserving storage of elegant Ince-Gaussian modes in warm atomic vapor

“…The elegant Hermite-Gaussian (eHG) mode is a self-similar solution of the coherent diffusion equation [23] , which enables it to resist motion-induced diffusion and keep its shape invariant during storage in the warm atomic vapor [24] . As another representative elegant mode, the elegant Ince-Gaussian (eIG) mode has attracted much research interest since it has an extra adjustable parameter (e.g., the ellipticity ε) and exhibits a continuous transition from the elegant Laguerre-Gaussian (eLG) mode to eHG mode as ε goes from zero to infinity [25,26] .…”