Transverse mode selection in a monolithic microchip laser

We outline an approach to mode selection in a microchip laser through judicious shaping of the pump light to create a high modal overlap with the desired mode. We demonstrate the principle by creating a donut-shaped pump profile in the focal plane of a converging lens, and use this profile to longitudinally pump a monolithic microchip laser where the output is a Laguerre-Gaussian mode of radial index p = 0 and azimuthal index l = 1 (LG(01)), or vortex beam, of power similar to 12 mW with a slope efficiency of 17%. This approach of diffractive pump shaping in the Fourier domain is advantageous as it allows for high pump intensity even with low pumping powers, thus ensuring sufficient gain is achieved for laser oscillation. (C) 2011 Elsevier B.V. All rights reserved.