Abstract

We have demonstrated that the orbitai angular momentum of photons is conserved in spontaneous parametric down-conversion. Three different values of the orbital angular momentum (-h,0,h) were realized by astigmatic mode conversion from a Hermite-Gaussian mode. The angular momentum of the down converted photons were analysed by mode-filters consisting on computer-generated Holograms and single mode fibres. An interestig feature of the experiment is that photon states with phase singularities can be created from pump fields without singularites.

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