Scalar doughnut mode beam is directly generated from an internal-cavity He-Ne laser. A spot-defect is created on a rear mirror to suppress a Gaussian mode. Intensity, phase and polarization distributions of the doughnut-mode are measured.
© 2012 OSA
S. Vyas, Y. Kozawa, and S. Sato, "Generation of Robust Doughnut Mode Beam from Internal Mirror He-Ne Laser," in Frontiers in Optics 2012/Laser Science XXVIII, OSA Technical Digest (online) (Optical Society of America, 2012), paper LW5I.6.