Multi-ring modes generation in Yb:YAG ceramic laser

A short-focus glass lens with strong spherical aberration was used for mode selection in the cw LD-end-pumped Yb:YAG ceramic laser. Sequence of low to very high order Laguerre–Gaussian (LG pl) modes with different combinations of radial, p and azimuthal, l indices ( p ⩽ 10, l ⩽ 28), with output beam diameters 2–13 mm and power up to 30 mW was obtained. Peaked and hollow multi-ring beams with near-diffraction free propagation of the central minimum or maximum over 40 m distance from the laser resonator were observed. Mechanisms of mode selection and possible applications of the proposed laser scheme are considered.