A method is proposed to eliminate the central hole present in the annular beams emitted by lasers equipped with unstable resonators. The method is based on the use of conical reflectors, or axicons. The first axicon is converging with a 45° cone angle; the second axicon is diverging with a 45° cone angle. The converging axicon has a central hole of diameter equal to the diameter of the diverging axicon. It can be shown that the combination of these two axicons yields an output laser beam with a near field of hyperbolic shape and a far field where 89% of power is contained in the central lobe. Inadequate axial positioning of the axicons or inappropriate values of the cone angles result in a degradation of the optical quality of the far field; the tolerance to such errors is evaluated for typical CO₂ laser parameters.

Date Published: 28 March 1989
PDF: 5 pages
Proc. SPIE 1024, Beam Diagnostics and Beam Handling Systems, (28 March 1989); doi: 10.1117/12.950184

Published in SPIE Proceedings Vol. 1024:
Beam Diagnostics and Beam Handling Systems
Alberto Sona, Editor(s)