The structure of sleeve beams generated by wide-aperture coaxial lasers has been numerically analyzed. The sleeve beams of sufficiently high intensity are used to brighten a medium and to ensure the waveguide propagation of sounding radiation inside the brightened channel. Numerical analysis was performed for the Yupiter laser. It is shown that its angular divergence is primarily determined by laws of geometric optics and the sleeve beam shape holds at any distance from the output aperture. The action of beam-forming optics of biconic axicon type and optical correction scheme based on a segmented mirror with controllable segments on the beam structure is examined. Results of numerical simulation have shown that the use of such a corrector allows the beam angular divergence to be decreased down to 10–3 rad.