Abstract
Non-diffraction beams can be obtained using a very small-width annular aperture that is placed in the back focal plane of a lens. However, since a rate of shielding of the annular aperture is very large, most incident waves are intercepted by the annular aperture. Therefore, the energy efficiency is very low. In this paper. the corn lens with a notch that generates a doughnut beam is loaded in front of the annular aperture to improve the energy efficiency. By numerical calculations, the relationships between the propagetion distance, the intensity of the non-diffraction beam and the rate of shielding of annuar aperture are examined.
