Generation of vortex beams from lasers with controlled Hermite- and Ince-Gaussian modes.

We report selective excitations of higher-order Hermite-Gaussian and Ince-Gaussian (IG) modes in a laser-diode-pumped microchip solidstate laser and controlled generation of corresponding higher-order and multiple optical vortex beams of different shapes using an astigmatic mode converter (AMC). Simply changing the pump-beam diameter, shape, and lateral off-axis position of the tight pump beam focus on the laser crystal within a microchip semispherical cavity can produce the desired optical vortex beams in a well controlled manner. Pattern changes featuring different IG and HG modes obtained by rotating the AMC are also demonstrated. Numerical simulation shows that the vortex structure is changed by controlled off-axis laser diode pumping, which could lead toward precise optical manipulation of small particles.