Experimental control of optical helicity in nanophotonics

Tischler, Nora; Fernandez‐Corbaton, Ivan; Zambrana‐Puyalto, Xavier; Minovich, Alexander; Vidal, Xavier; Juan, Mathieu L.; Molina‐Terriza, Gabriel

doi:10.1038/lsa.2014.64

Cited by 44 publications

(61 citation statements)

References 23 publications

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“…like to emphasize that this simple relation between helicity and polarization is only valid because, as mentioned previously, we are describing the system in the paraxial regime 26 . When the paraxial approximation does not hold, the polarization of the field and helicity can no longer be so simply related 24 .…”

Section: Discussionmentioning

confidence: 95%

Angular momentum-induced circular dichroism in non-chiral nanostructures

2014

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Circular dichroism, that is, the differential absorption of a system to left and right circularly polarized light, is one of the only techniques capable of providing morphological information of certain samples. In biology, for instance, circular dichroism spectroscopy is widely used to study the structure of proteins. More recently, it has also been used to characterize metamaterials and plasmonic structures. Typically, circular dichorism can only be observed in chiral objects. Here we present experimental results showing that a non-chiral sample such as a subwavelength circular nanoaperture can produce giant circular dichroism when a vortex beam is used to excite it. These measurements can be understood by studying the symmetries of the sample and the total angular momentum that vortex beams carry. Our results show that circular dichroism can provide a wealth of information about the sample when combined with the control of the total angular momentum of the input field.

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Section: Discussionmentioning

confidence: 95%

Angular momentum-induced circular dichroism in non-chiral nanostructures

2014

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“…Finally, we note that the generation and measurement of pure helicity modes in the collimated regime at optical frequencies is straightforward and can be done with polarizers and quarter wave-plates [64,71], and that microscope objectives designed to meet the aplanatic approximation preserve helicity [64, App. C], which makes them suitable as focusing and collecting lenses in the proposed measurement scheme.…”

Section: A Double Resonantly Enhanced Circular Dichroism Setupmentioning

confidence: 99%

Objects of Maximum Electromagnetic Chirality

Fernandez‐Corbaton¹,

Fruhnert²,

Rockstuhl³

2016

Phys. Rev. X

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108

176

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We introduce a definition of the electromagnetic chirality of an object and show that it has an upper bound. Reciprocal objects attain the upper bound if and only if they are transparent for all the fields of one polarization handedness (helicity). Additionally, electromagnetic duality symmetry, i.e. helicity preservation upon interaction, turns out to be a necessary condition for reciprocal objects to attain the upper bound. We use these results to provide requirements for the design of such extremal objects. The requirements can be formulated as constraints on the polarizability tensors for dipolar objects or on the material constitutive relations for continuous media. We also outline two applications for objects of maximum electromagnetic chirality: A twofold resonantly enhanced and background free circular dichroism measurement setup, and angle independent helicity filtering glasses. Finally, we use the theoretically obtained requirements to guide the design of a specific structure, which we then analyze numerically and discuss its performance with respect to maximal electromagnetic chirality.

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“…It is also worth remarking that there is a considerable interest to artificial media and materials that restore the dual symmetry of vacuum on the level of macroscopic medium parameters (e.g., =µ) [19,107,108,214,[234][235][236]. The conservation of the optical helicity associated with such symmetry (see Section 8.8 below) provides a new insight into the light propagation and scattering dynamics.…”

Section: Macroscopic Maxwell's Equationsmentioning

confidence: 99%

Spacetime algebra as a powerful tool for electromagnetism

2015

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We present a comprehensive introduction to spacetime algebra that emphasizes its practicality and power as a tool for the study of electromagnetism. We carefully develop this natural (Clifford) algebra of the Minkowski spacetime geometry, with a particular focus on its intrinsic (and often overlooked) complex structure. Notably, the scalar imaginary that appears throughout the electromagnetic theory properly corresponds to the unit 4-volume of spacetime itself, and thus has physical meaning. The electric and magnetic fields are combined into a single complex and frame-independent bivector field, which generalizes the Riemann-Silberstein complex vector that has recently resurfaced in studies of the single photon wavefunction. The complex structure of spacetime also underpins the emergence of electromagnetic waves, circular polarizations, the normal variables for canonical quantization, the distinction between electric and magnetic charge, complex spinor representations of Lorentz transformations, and the dual (electric-magnetic field exchange) symmetry that produces helicity conservation in vacuum fields. This latter symmetry manifests as an arbitrary global phase of the complex field, motivating the use of a complex vector potential, along with an associated transverse and gauge-invariant bivector potential, as well as complex (bivector and scalar) Hertz potentials. Our detailed treatment aims to encourage the use of spacetime algebra as a readily available and mature extension to existing vector calculus and tensor methods that can greatly simplify the analysis of fundamentally relativistic objects like the electromagnetic field.Comment: 119 pages, 20 tables, 7 figures. v3: to appear in Physics Report

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Experimental control of optical helicity in nanophotonics

Cited by 44 publications

References 23 publications

Angular momentum-induced circular dichroism in non-chiral nanostructures

Angular momentum-induced circular dichroism in non-chiral nanostructures

Objects of Maximum Electromagnetic Chirality

Spacetime algebra as a powerful tool for electromagnetism

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