The doughnut mode is of great importance in optical tweezers and spanners. Such mode is generated by transforming the Hermite-Gaussian mode of a laser-diode end-pumped Nd:YAG laser through a rotated cylindrical lens system. The field distribution and the intensity profile of the doughnut mode were calculated theoretically from the field of the input Hermite-Gaussian mode. The beam transformation was confirmed in the experiments.
Chunqing Gao, Chunqing Gao,
"New doughnut mode for optical tweezers and spanners", Proc. SPIE 4224, Biomedical Photonics and Optoelectronic Imaging, (11 October 2000); doi: 10.1117/12.403920; https://doi.org/10.1117/12.403920