Angular momentum-carrying radially-polarised twisted light

TY - JOUR

T1 - Angular momentum-carrying radially-polarised twisted light

AU - Babiker, M.

AU - Koksal, K.

AU - Lembessis, V. E.

N1 - Funding Information: The authors wish to thank Professors S. Franke-Arnold, K.D. Dholakia, M. Mansuripur, E.J. Galvez, Q. Zhan, G. Milione and P. Banzer for useful correspondence. © 2023 Published by Elsevier B.V. This is an author-produced version of the published paper. Uploaded in accordance with the publisher’s self-archiving policy.

PY - 2023/6/15

Y1 - 2023/6/15

N2 - It is well-known that the fields of pure radially-polarised optical vortex modes do not possess the usual phase function eiℓϕ of typical twisted light and so they do not carry angular momentum. However, recent work has confirmed that radially-polarised modes with helical wave fronts have been created in the laboratory by several groups and they can now be readily generated using commercially available devices. They are endowed with the phase function eiℓϕ for arbitrary values of the winding number ℓ. Crucially, the original theoretical treatments disregard the longitudinal electric and magnetic field components. We show here that the longitudinal components must be included, not just for the consistency of the treatment, but because only this can lead to angular momentum. We show that for such created modes the cycle-averaged angular momentum is αħℓ where α=(Pw02)/(ħc2) is a dimensionless constant, with P the power in the mode and w0 the mode width at focus.

AB - It is well-known that the fields of pure radially-polarised optical vortex modes do not possess the usual phase function eiℓϕ of typical twisted light and so they do not carry angular momentum. However, recent work has confirmed that radially-polarised modes with helical wave fronts have been created in the laboratory by several groups and they can now be readily generated using commercially available devices. They are endowed with the phase function eiℓϕ for arbitrary values of the winding number ℓ. Crucially, the original theoretical treatments disregard the longitudinal electric and magnetic field components. We show here that the longitudinal components must be included, not just for the consistency of the treatment, but because only this can lead to angular momentum. We show that for such created modes the cycle-averaged angular momentum is αħℓ where α=(Pw02)/(ħc2) is a dimensionless constant, with P the power in the mode and w0 the mode width at focus.

KW - Angular momentum

KW - Radially-polarised

UR - http://www.scopus.com/inward/record.url?scp=85151282650&partnerID=8YFLogxK

U2 - 10.1016/j.optcom.2023.129469

DO - 10.1016/j.optcom.2023.129469

M3 - Article

AN - SCOPUS:85151282650

SN - 0030-4018

VL - 537

JO - Optics Communications

JF - Optics Communications

M1 - 129469

ER -