Nonlinear ring structures in forward scattering of resonant monochromatic laser radiation

Abstract

We present experimental and theoretical investigations of a Gaussian laser beam interacting with Zeeman-tuned J=1\ensuremath{\rightarrow}J=0 atomic systems. In our experiment a single-mode cw dye-laser beam traverses a neon discharge in a longitudinal magnetic field. The excited neon transitions used for these studies are 1${\mathit{s}}_{4}$(J=1,g=1.464)\ensuremath{\rightarrow}2${\mathit{p}}_{3}$(J=0) and 1${\mathit{s}}_{2}$(J=1,g=1.034)\ensuremath{\rightarrow}2${\mathit{p}}_{1}$(J=0). In the laser-induced forward-scattered light, dark and bright ring-shaped structures are observed. The ring structures are investigated as a function of the magnetic detuning of the m=\ifmmode\pm\else\textpm\fi{}1 sublevels and as a function of the laser-beam power. We find that the line shapes of the spectra, i.e., the forward-scattered light intensities as a function of the magnetic detuning, are sensitive to the transverse intensity distribution of the laser beam. Analytical expressions based on a semiclassical theory are derived and the calculated results on the ring structures and the spectra are compared with the experimental results. Good agreement between the calculated and the experimental results are obtained only when the transverse effects are taken into account.