Second Harmonic Generation and the Orbital Angular Momentum of Light

Abstract

The orbital angular momentum of light is distinct from the angular momentum associated with the spin or polarisation state of the light. Thus linearly polarised modes can carry angular momentum. Laguerre-Gaussian laser modes have been identified as a class of modes that can possess such orbital angular momentum. Hermite-Gaussian modes may be converted to Laguerre-Gaussian modes, characterised by two integer indices l and p, by the use of a mode converter. The l index occurs in the azimuthal phase factor eil ϕ in the field distribution of Laguerre-Gaussian beams which possess an orbital angular momentum equivalent to lħ per photon 1.