Efficient conversion of a radially polarized beam to a nearly Gaussian beam

We demonstrate an efficient method for transformation of a radially polarized Laguerre-Gaussian beam to a nearly Gaussian beam with much higher beam quality. The method is based on separation of the radially polarized mode into two degenerate modes and coherent addition of the modes after phase flattening. We transformed a high-power Nd:YAG radially polarized (0,1)(*) Laguerre-Gaussian beam with M(2)=2.52 and power of 30 W into a nearly Gaussian beam with M(2)=1.3. As a result, the brightness increased by a factor of approximately 2.5.