2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/85349Doughnut shaped light beam has been generated from Gaussian mode ($TEM_{00}$) cw-Ti sapphire laser. After splitting the pump beam into two equal intensity components and introducing unequal convergence and phase delay while they are recombined it results in doughnut mode. Such a beam is tunable and have long propagation length. The evanescent field generated by 360 mW (at 780 nm wavelength) of such a beam creates optical field of 600 nm decay length with a 5.75 neV repulsive dipole potential. Thus cold Rb atoms (at 10{$μ$}K or less temperature) released from MOT can be reflected by the surface so that the atoms are collected ultimately at the bottom of the prism. By focussing such doughnut beam with 8 cm focal length converging lens, the dark radius reduces to 22{$μ$}. We also observe such beam to contain azimuthal phase as well as radial phase distribution.17 pages, 6 figuresOpticstext