An optical system for producing a structured optical beam, the system comprising: a convex lens having a spherical or cylindrical entry surface, the 5 lens comprising a material having a refractive index of at least 1.6, an electromagnetic radiation source configured to provide a substantially coherent beam of electromagnetic radiation, wherein the source is arranged to illuminate the convex lens over a selected illumination fraction of the spherical or cylindrical entry surface and with 10 a corresponding selected focus of the illuminating beam such that the beam traverses a sufficient refractive volume of the convex lens to produce aberrations in the beam emerging from the convex lens such that it comprises a structured optical beam. The system and method allows for generating a structured beam which has the potential to propagate over the large distances while maintaining a 15 well-defined cross-section intensity distribution.