Abstract:
We obtain explicit equations for the distance at which the Airy beam, limited in initial plane (from the side where amplitude drops slowly), propagates along the parabolic trajectory without changing its amplitude (i.e. almost diffraction-free). Analogical distance for diffraction-free Bessel beam is proportional to the radius of the circular diaphragm which limits the beam and inversely proportional to the tangent of the slope of the conical wave which generates the Bessel beam. This distance is wavelength-independent. For the Airy beam this distance is proportional to the square root of the module coordinate of the diaphragm edge and inversely proportional to the wavelength of light.