From Huygens-Fresnel integral in cylindrical coordinates and by conveniently choosing the phase function from energy considerations, we demonstrate the possibility of approximately achieving and almost freely chosen longitudinal intensity profile along the optical axis for Free Space Optics (FSO) using a simple theory. These phase functions represent optical elements that could be coupled to the transmitter and, in the case of this work, it is shown that axicons and gradient-index (GRIN) axicons, which are commercially available and cost-effective, can be easily designed for applications in FSO systems to overcome diffraction and possible atmospheric attenuations, to increase the link distance or to diminish the power emitted. © 2006 IEEE.