Abstract
We present an in-depth analysis of the resonant intermixing between optical orbital and spin angular momentum of Laguerre-Gaussian (LG) beams, mediated by chiral clusters made of silicon nanospheres. In particular, we establish a relationship between the spin and orbital quantum numbers characterizing the LG beam and the order q of the rotation symmetry group 𝒞q of the cluster of nanospheres for which resonantly enhanced coupling between the two components of the optical angular momentum is observed. Thus, similar to the case of diffraction grating-mediated transfer of linear momentum between optical beams, we demonstrate that clusters of nanospheres that are invariant to specific rotation transformations can efficiently transfer optical angular momentum between LG beams with different quantum numbers. We also discuss the conditions in which the resonant interaction between LG beams and a chiral cluster of nanospheres leads to the generation of superchiral light.
Highlights
Over the last decade, we have witnessed a tremendous growth of research interest in spin-orbit interactions (SOI) of light [1,2,3,4], both because of the implications of SOI related phenomena to our understanding of fundamental principles of optics and basic properties of light, as well as their potential technological applications to nanophotonics, microfluidics, optical microscopy, optical communications, and quantum information processing
We have demonstrated that nanophotonic structures made of all-dielectric resonators can be efficiently employed in creating optical fields with specific characteristics of their optical angular momentum
Our theoretical analysis has revealed that by using silicon nanospheres arranged in clusters that are invariant to specific rotation transformations one can resonantly enhance or suppress the transfer of optical angular momentum from incident plane waves or more complex optical beams, such as Laguerre-Gaussian beams, to scattered fields with specific values of the orbital and spin angular momentum
Summary
We have witnessed a tremendous growth of research interest in spin-orbit interactions (SOI) of light [1,2,3,4], both because of the implications of SOI related phenomena to our understanding of fundamental principles of optics and basic properties of light, as well as their potential technological applications to nanophotonics, microfluidics, optical microscopy, optical communications, and quantum information processing. The research in the physics of SOI has been greatly facilitated by the availability of optical beams with well-defined angular momentum, which in the paraxial approximation can be naturally decomposed in an orbital and spin part. One such salient example is Laguerre–Gaussian, LGpl, beams whose intensity profile in the transverse plane shows a concentric ring-like structure with p + 1 maxima and azimuthal phase dependence eilφ , p and l being the radial and azimuthal indices, respectively. In the last section, we summarize the main conclusions of our work
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