Angular momentum of focused beams: Beyond the paraxial approximation

Monteiro, Paula B.; Neto, Paulo A. Maia; Nussenzveig, H. M.

doi:10.1103/physreva.79.033830

Cited by 99 publications

(112 citation statements)

References 41 publications

(67 reference statements)

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“…In order to avoid any possible ambiguity that may arise from the AM density [30,31], I do not use this notion here. In fact, we have given in Eqs.…”

Section: Am Properties Of Non-paraxial Beamsmentioning

confidence: 99%

Spin and orbital angular momentum of a class of nonparaxial light beams having a globally defined polarization

2009

Phys. Rev. A

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It is shown that the momentum density of free electromagnetic field splits into two parts. One has no contribution to the net momentum due to the transversality condition. The other yields all the momentum. The angular momentum that is associated with the former part is spin, and the angular momentum that is associated with the latter part is orbital angular momentum. Expressions for the spin and orbital angular momentum are given in terms of the electric vector in reciprocal space. The spin and orbital angular momentum defined this way are used to investigate the angular momentum of nonparaxial beams that are described in a recently published paper [Phys. Rev. A 78, 063831 (2008)]. It is found that the orbital angular momentum depends, apart from an l-dependent term, on two global quantities, the polarization represented by a generalized Jones vector and a new characteristic represented by a unit vector I, though the spin depends only on the polarization. The polarization dependence of orbital angular momentum through the impact of I is obtained and discussed. Some applications of the result obtained here are also made. The fact that the spin originates from the momentum density that has no contribution to the net momentum is used to show that there does not exist the paradox on the spin of circularly polarized plane wave. The polarization dependence of both spin and orbital angular momentum is shown to be the origin of conversion from the spin of a paraxial Laguerre-Gaussian beam into the orbital angular momentum of the focused beam through a high numerical aperture.

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“…In order to avoid any possible ambiguity that may arise from the AM density [30,31], I do not use this notion here. In fact, we have given in Eqs.…”

Section: Am Properties Of Non-paraxial Beamsmentioning

confidence: 99%

Spin and orbital angular momentum of a class of nonparaxial light beams having a globally defined polarization

2009

Phys. Rev. A

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“…Regarding the magnitude of the fields near r = 0 Zurita-Sánchez et al [30] have shown that, for the strongly focused azimuthally- polarized beam they studied, the magnetic interaction overcomes the electric interaction near the phase singularity; recently, their findings have been corroborated by the theoretical study of Klimov et al [49] in the case of focused Laguerre-Gaussian beams. Finally, in their research on highly-focused TL beams, Monteiro et al [63], Iketaki et al [59] and Klimov et al [49] report that interesting effects only occur when ℓ = 1, 2 and σ = −1. The overall similarities are no coincidence, for the vector potential Eq.…”

Section: Figmentioning

confidence: 97%

Formulation of the twisted-light–matter interaction at the phase singularity: The twisted-light gauge

2015

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Twisted light is light carrying orbital angular momentum. The profile of such a beam is a ring-like structure with a node at the beam axis, where a phase singularity exists. Due to the strong spatial inhomogeneity the mathematical description of twisted-light-matter interaction is non-trivial, in particular close to the phase singularity, where the commonly used dipole-moment approximation cannot be applied. In this paper we show that, if the handedness of circular polarization and the orbital angular momentum of the twisted-light beam have the same sign, a Hamiltonian similar to the dipole-moment approximation can be derived. However, if the signs differ, in general the magnetic parts of the light beam become of significant importance and an interaction Hamiltonian which only accounts for electric fields is inappropriate. We discuss the consequences of these findings for twisted-light excitation of a semiconductor nanostructures, e.g., a quantum dot, placed at the phase singularity.

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“…The intrinsic photonic SOI effect can also happen in nonparaxial light, e.g., light scattering by small particles136–144 (Figure 5c), or light focusing by high numerical aperture (NA) lenses136,145–151 (Figure 5d), or a combination of the focusing and scattering processes in high NA imaging of small particles 136. The SAM‐IOAM interaction in this effect can generate spin‐dependent optical vortex and thus induce SOAM conversions 137,140,146,147,149,150,152–154.…”

Section: Photonic Spin–orbit Interactionsmentioning

confidence: 99%

Chiral Coupling of Valley Excitons and Light through Photonic Spin–Orbit Interactions

Chen

Fan

et al. 2019

Advanced Optical Materials

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Spintronics employs the spin of electrons to encode information. Akin to spintronics, valleytronics exploits the valley as pseudospin‐carrying controllable binary information. 2D transition metal dichalcogenides (TMDCs) have asymmetric +K and −K valleys. The valley pseudospins of these materials can be manipulated by selective pumping, giving rise to valley‐dependent circularly polarized photoluminescence. The photonic spin–orbit interactions (SOIs) in nanophotonic systems allow the transformation or coupling of optical spin angular momentum to orbital angular momentum of light. Hybridizing 2D TMDC electronic systems with nanophotonic systems can open up an avenue for merging TMDC valley polarization and photonic SOIs to uncover new mechanisms of on‐chip optical information processing and transport. This review focuses on the fundamentals and implications of TMDC valley polarization, photonic SOI effects, and their chiral coupling in hybrid TMDCs–nanophotonic systems. First, the deterministic valley‐dependent optical properties of TMDCs and recent efforts in achieving large valley polarization contrast are reviewed. Then, various SOI effects in nanophotonic systems and their physical mechanisms are summarized. At the end, recent demonstrations of chiral coupling between TMDC valley excitons and light through spin‐direction locking at hybrid interfaces are highlighted.

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Angular momentum of focused beams: Beyond the paraxial approximation

Cited by 99 publications

References 41 publications

Spin and orbital angular momentum of a class of nonparaxial light beams having a globally defined polarization

Spin and orbital angular momentum of a class of nonparaxial light beams having a globally defined polarization

Formulation of the twisted-light–matter interaction at the phase singularity: The twisted-light gauge

Chiral Coupling of Valley Excitons and Light through Photonic Spin–Orbit Interactions

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