Abstract

Optical coatings that show a gradually varying performance (reflectance, transmittance, etc.) along the coated surface are known as graded coatings. They are mainly used in the laser field as output couplers of unstable laser resonators [1,2,3]. The replacement of traditional laser mirrors, that have a high reflecting area delimited by sharp edges, with graded reflectance mirrors permits the achievement of diffraction-limited beams of high power or energy. The use of traditional hard-edge mirrors in unstable resonators gives output laser beams having a near-field profile with pronounced ripples due to the diffraction at the mirror edge and a far-field pattern with noticeable side lobes. These shortcomings can be avoided by using output couplers with a graded reflectance profile described by a predefined law, in most cases the reflectance against the radius is represented by a Gaussian or super-Gaussian equation.

© 1995 Optical Society of America