Generation of continuously tunable fractional optical orbital angular momentum using internal conical diffraction

D. P. O'Dwyer, C. F. Phelan, Y. P. Rakovich, P. R. Eastham, J. G. Lunney, J. F. Donegan
2010 Optics Express  
When a left-circularly polarised Gaussian light beam, which has spin angular momentum (SAM) J sp = σħ = 1ħ per photon, is incident along one of the optic axes of a slab of biaxial crystal it undergoes internal conical diffraction and propagates as a hollow cone of light in the crystal. The emergent beam is a superposition of equal amplitude zero and first order Bessel like beams. The zero order beam is left-circularly polarised with zero orbital angular momentum (OAM) J orb = ℓħ = 0, while the
more » ... irst order beam is right-circularly polarized but carries OAM of J orb = 1ħ per photon. Thus, taken together the two beams have zero SAM and J orb = ½ħ per photon. In this paper we examine internal conical diffraction of an elliptically polarised beam, which has fractional SAM, and demonstrate an all-optical process for the generation light beams with fractional OAM up to ± 1ħ
doi:10.1364/oe.18.016480 pmid:20721035 fatcat:ghv5wkqpzbdvpdfvizte363sle