Discontinuous phase elements for transverse mode selection in laser resonators

Discontinuous phase elements can be inserted into laser resonators so that the lasers will operate with only one desired high order transverse mode. T hese elements introduce sharp discontinuous phase changes so as to result i n minimal losses for a desired transverse mode but high losses to others. T he basic principles, along with experimental results with Nd:yttrium-alumin um-garnet and CO2 lasers, illustrating improved output powers with a high b eam quality of low divergence, are presented. (C) 1999 American Institute o f Physics. [S0003-6951(99)02610-8].