The creation and annihilation of optical vortices using cascade conical diffraction O'Dwyer, D. P. ; Phelan, C. F. ; Rakovich, Y. P. ; Eastham, P. R. ; Lunney, J. G. ; Donegan, J. F. Abstract Publication: Optics Express Pub Date: January 2011 DOI: 10.1364/OE.19.002580 Bibcode: 2011OExpr..19.2580O