Generation of pure TEMp0 modes using a friendly intracavity laser beam shaping technique

A variant of the Fox & Li method performing intra-cavity laser beam shaping for resonators containing an arbitrary number of amplitude and phase diffractive optics is presented. As an illustration, the problem of forcing a laser to oscillate on a single high-order transverse mode has been considered. In particular, from numerical simulation, we deduce a simple model for generating such modes with a pi-phase plate inserted into a plano-concave cavity. This model has been tested experimentally within an active cavity with a diode-pumped Nd:YVO4 laser and an excellent agreement with numerical predictions has been found: a phase aperture located quite close to the concave mirror, and whose normalized radius κ is so that 2κ2 corresponds to a zero of the desired p-order Laguerre polynomial, was sufficient to generate single cylindrical TEMp0 modes (p = 1, 2, 3) as long as its radius is correctly chosen. The laser based on the optimized features was perfectly stable, whatever the order of the generated mode.