Controlling the handedness of directly excited Laguerre Gaussian modes in a solid-state laser

The first higher order Laguerre-Gaussian (LG₀₁) beam is characterised by a donut-shaped intensity profile and has a phase front that advances with a helical trajectory described by exp(±iφ-ikz), where φ is the azimuthal angle and z is the axial position. As a consequence, the LG₀₁ beam has an orbital angular momentum of ±ħ for each photon. These unique properties of LG₀₁ beams have attracted growing interest due to a wealth of promising applications in areas such as optical manipulation of particles, trapping and guiding of atoms and laser processing of materials. A number of different techniques for generating LG₀₁ beams have been devised over the years. The most popular techniques exploit external beam-shaping arrangements. However, these techniques are generally not suitable for high power operation due to power handling limitations.