Unidirectional evanescent-wave coupling from circularly polarized electric and magnetic dipoles: An angular spectrum approach

Picardi, Michela F.; Manjavacas, Alejandro; Zayats, Anatoly V.; Rodríguez-Fortuño, Francisco J.

doi:10.1103/physrevb.95.245416

Cited by 75 publications

(91 citation statements)

References 53 publications

(104 reference statements)

Supporting

Mentioning

Contrasting

Order By: Relevance

“…[51,52], will gain relevance in upcoming experimental and theoretical studies, similar to the spin-momentum locking of spinning electric dipoles [1][2][3]7]. Especially in the field of silicon-based nanophotonics [35][36][37], the spin-momentum locking of combined electric and magnetic dipoles represents a promising route towards signal routing and polarization multiplexing at the nanoscale.…”

Section: Discussionmentioning

confidence: 99%

Magnetic and Electric Transverse Spin Density of Spatially Confined Light

et al. 2018

View full text Add to dashboard Cite

When a beam of light is laterally confined, its field distribution can exhibit points where the local magnetic and electric field vectors spin in a plane containing the propagation direction of the electromagnetic wave. The phenomenon indicates the presence of a nonzero transverse spin density. Here, we experimentally investigate this transverse spin density of both magnetic and electric fields, occurring in highly confined structured fields of light. Our scheme relies on the utilization of a highrefractive-index nanoparticle as a local field probe, exhibiting magnetic and electric dipole resonances in the visible spectral range. Because of the directional emission of dipole moments that spin around an axis parallel to a nearby dielectric interface, such a probe particle is capable of locally sensing the magnetic and electric transverse spin density of a tightly focused beam impinging under normal incidence with respect to said interface. We exploit the achieved experimental results to emphasize the difference between magnetic and electric transverse spin densities.

show abstract

Section: Discussionmentioning

confidence: 99%

Magnetic and Electric Transverse Spin Density of Spatially Confined Light

et al. 2018

View full text Add to dashboard Cite

show abstract

“…The coupling of a dipole to a waveguide can be understood via Fermi's Golden Rule, where directional excitation of modes is interpreted as destructive interference between different dipolar components. The same phenomenon can be described using the angular spectrum representation of a source, also called spatial spectrum or momentum representation. The electric field of a source can be expanded in momentum space via its angular spectrum:

E false(x, y, z false) = -3pt \int -3pt \int E false(k_{x}, k_{y}, z false) e^{i (k_{x} x + k_{y} y)} d k_{x} d k_{y},

where x , y , z represent the spatial position, with z being an arbitrary direction perpendicular to the plane in which we performed a 2D Fourier transform, and

k_{x}

and

k_{y}

represent the transverse wave‐vector components.…”

Section: Source Angular Spectrummentioning

confidence: 99%

“…The angular spectra of dipolar sources can be obtained from Weyl's identity, and is typically expressed using dyadic Green functions . The spectra of dipoles can be re‐written in an exact vector form describing the entire angular spectrum, including far‐ and near‐fields as:

{boldE}^{\pm} false(k_{x}, k_{y} false) = \frac{i k^{2}}{8 π^{2} ε} [({boldv}^{\pm} \cdot {\overset{e}{true}}_{s}) {\hat{bolde}}_{s} + ({boldv}^{\pm} \cdot {\overset{e}{true}}_{p}^{\pm}) {\hat{bolde}}_{p}^{\pm}],

where

v^{\pm}

depends on the wave‐vector and on both the electric

boldp

and magnetic

boldm

dipole moments of the source:

{boldv}^{\pm} = \frac{1}{k_{z}} [boldp - (() {\overset{e}{true}}_{k}^{\pm} \times \frac{boldm}{c})],

where

{\overset{e}{true}}_{k}^{\pm} = {boldk}^{\pm} / k

and

{boldk}^{\pm} = false(k_{x}, k_{y}, \pm k_{z} false)

. When Equation is applied to a given dipole

boldp

and

boldm

, four spectra may be calculated and plotted, corresponding to

E_{p}^{+}

E_{s}^{+}

E_{p}^{-}

, and

E_{s}^{-}

.…”

Section: Calculating Dipolar Angular Spectramentioning

confidence: 99%

Amplitude and Phase Control of Guided Modes Excitation from a Single Dipole Source: Engineering Far‐ and Near‐Field Directionality

Picardi

Zayats

Rodríguez-Fortuño

2019

Laser & Photonics Reviews

View full text Add to dashboard Cite

The design of far‐field radiation diagrams from combined electric and magnetic dipolar sources has recently found applications in nanophotonic metasurfaces that realize tailored reflection and refraction. Such dipolar sources also exhibit important near‐field evanescent coupling properties with applications in polarimetry and quantum optics. Here, a rigorous theoretical framework is introduced for engineering the angular spectra encompassing both far‐ and near‐fields of electric and magnetic sources and a unified description of both free space and guided mode directional radiation is developed. The approach uses the full parametric space of six complex‐valued components of magnetic and electric dipoles in order to engineer constructive or destructive near‐field interference. Such dipolar sources can be realized with dielectric or plasmonic nanoparticles. It is shown how a single dipolar source can be designed to achieve the selective coupling to multiple waveguide modes and far‐field simultaneously with a desired amplitude, phase, and direction.

show abstract

“…In the phase matching argument above, we pointed out from an intuitive and hand-wavy argument that the phase fronts of a circularly polarized dipole sweep from left to right when looking below the dipole, explaining its directionality. Indeed, the angular spectrum of such dipole reveals the dominance of evanescent components with wave-vectors k pointing from left to right when looking from below the dipole [15], providing a solid quantitative foundation to our intuitive notion. Janus and Huygens dipoles exhibit similar imbalances in their angular spectra, fully explaining their behaviour and symmetries.…”

Section: We May Then Analyse This Field By Means Of Its Spatial Foumentioning

confidence: 99%

“…It is most powerful when the dipole is placed near smooth interfaces which conserve momentum and thus allow us to apply phase matching arguments. With it, we realize that the directionality of the dipole is a property of the dipole itself, universal for any waveguide [15]. It is based on a careful analysis of the fields produced by a dipole [16], whose exact analytical form has been known for as long as Maxwell's equations themselves.…”

Section: An G U L a R S P E C T R U M O F T H E Dipolar Fieldsmentioning

confidence: 99%