Ultra-thin plasmonic optical vortex plate based on phase discontinuities

Genevet, Patrice; Yu, Nanfang; Aieta, Francesco; Lin, Jiao; Kats, Mikhail A.; Blanchard, Romain; Scully, Marlan O.; Gaburro, Z.; Capasso, Federico

doi:10.1063/1.3673334

Cited by 478 publications

(315 citation statements)

References 18 publications

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“…[7][8][9][10][11][12][13][14] An array of such nanoantennas can form a metasurface to bend the light abnormally 7,8 in a fairly broad range of wavelengths and can create, for example, an optical vortex beam. 7,12 In addition, a metasurface arranged of plasmonic nano-antennas can be used as a very efficient coupler between propagating waves and surface waves. 10 These phase-shifting, plasmonic nano-antennas also can be used to build optical lenses with surprising properties.…”

Section: Introductionmentioning

confidence: 99%

Ultra-thin, planar, Babinet-inverted plasmonic metalenses

et al. 2013

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We experimentally demonstrate the focusing of visible light with ultra-thin, planar metasurfaces made of concentrically perforated, 30-nm-thick gold films. The perforated nano-voids-Babinet-inverted (complementary) nano-antennas-create discrete phase shifts and form a desired wavefront of cross-polarized, scattered light. The signal-to-noise ratio in our complementary nano-antenna design is at least one order of magnitude higher than in previous metallic nano-antenna designs. We first study our proof-of-concept 'metalens' with extremely strong focusing ability: focusing at a distance of only 2.5 mm is achieved experimentally with a 4-mm-diameter lens for light at a wavelength of 676 nm. We then extend our work with one of these 'metalenses' and achieve a wavelength-controllable focal length. Optical characterization of the lens confirms that switching the incident wavelength from 676 to 476 nm changes the focal length from 7 to 10 mm, which opens up new opportunities for tuning and spatially separating light at different wavelengths within small, micrometer-scale areas. All the proposed designs can be embedded on-chip or at the end of an optical fiber. The designs also all work for two orthogonal, linear polarizations of incident light.

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Section: Introductionmentioning

confidence: 99%

Ultra-thin, planar, Babinet-inverted plasmonic metalenses

et al. 2013

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“…Nano-fabrication advances have enabled the development of metamaterials capable of unconventionally controlling the flow of electromagnetic energy in the subwavelength domain. 12,13 Recent demonstrations of ultrathin lenses, axicons 14 and spiral phase plates 15 use arrays of nano-antennas with different shapes to control the phase of optical fields. 16 Particular arrangements of nanoparticles have also exhibited similar phase control.…”

Section: Introductionmentioning

confidence: 99%

Generating optical orbital angular momentum at visible wavelengths using a plasmonic metasurface

et al. 2014

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Light beams with a helical phase-front possess orbital angular momentum along their direction of propagation in addition to the spin angular momentum that describes their polarisation. Until recently, it was thought that these two 'rotational' motions of light were largely independent and could not be coupled during light-matter interactions. However, it is now known that interactions with carefully designed complex media can result in spin-to-orbit coupling, where a change of the spin angular momentum will modify the orbital angular momentum and vice versa. In this work, we propose and demonstrate that the birefringence of plasmonic nanostructures can be wielded to transform circularly polarised light into light carrying orbital angular momentum. A device operating at visible wavelengths is designed from a space-variant array of subwavelength plasmonic nano-antennas. Experiment confirms that circularly polarised light transmitted through the device is imbued with orbital angular momentum of 62" (with conversion efficiency of at least 1%). This technology paves the way towards ultrathin orbital angular momentum generators that could be integrated into applications for spectroscopy, nanoscale sensing and classical or quantum communications using integrated photonic devices. Keywords: light orbital angular momentum; light spin angular momentum; plasmonic metasurface INTRODUCTION Spin angular momentum (SAM) and orbital angular momentum (OAM) are associated with the polarisation and phase of the optical field, respectively. 1 A striking difference between these momenta is the range of allowed values. SAM can be 6" per photon, expressed as left or right circular polarisation, while OAM has an unbounded value of '" per photon, 2 ' being an integer. In an anisotropic and inhomogeneous medium, these otherwise independent momenta can be made to interact, changing both the polarisation and phase of the beam. 3 This change depends on the incident beam's polarisation and the medium's topology stemming from its inhomogeneity. This relationship can be described by the Pancharatnam-Berry (geometrical) phase, 4 and is what allows a beam to experience different optical paths associated with the trajectory of the polarisation evolution on the Poincaré sphere. 5 Recently, this phenomenon has enabled PancharatnamBerry phase optical elements: 6,7 devices that control the output beam's wavefront according to the polarisation of the input beam. These devices could easily be inserted into the beam path of existing spectroscopic, nano-imaging or communication systems, as they do not rely on diffraction, adding OAM-based functionality that has the potential to distinguish between molecules of different chirality, enhance optical circular dichroism 8 and encode multiple bits of information onto a single photon. 9 Existing Pancharatnam-Berry phase optical elements include qplates, 3 made of liquid crystals, and computer-generated subwavelength gratings, 6,10 made of micron-size dielectric features. These

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“…1,2 They are typically structured at the subwavelength scale with ultrathin metallic or dielectric micro/nanoparticles or with holes opened in metallic films. Metamaterials exhibit unprecedented degrees of freedom in the polarization and phase manipulation of light via the geometric structuring of their structural units, especially on the wavelength scale, [3][4][5][6][7][8][9] which leads to applications such as vortex beam generators, 3,7 metalenses 10,11 and optical holography. 12,13 These materials also offer considerable potential for the manipulation of the angular moment of light and the photonic spin Hall effect (SHE), thereby providing convenient opportunities for spin-polarized photonics and nanophotonics.…”

Section: Introductionmentioning

confidence: 99%

Giant photonic spin Hall effect in momentum space in a structured metamaterial with spatially varying birefringence

et al. 2015

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The photonic spin Hall effect (SHE) in the reflection and refraction at an interface is very weak because of the weak spin-orbit interaction. Here, we report the observation of a giant photonic SHE in a dielectric-based metamaterial. The metamaterial is structured to create a coordinate-dependent, geometric Pancharatnam-Berry phase that results in an SHE with a spin-dependent splitting in momentum space. It is unlike the SHE that occurs in real space in the reflection and refraction at an interface, which results from the momentum-dependent gradient of the geometric Rytov-Vladimirskii-Berry phase. We theorize a unified description of the photonic SHE based on the two types of geometric phase gradient, and we experimentally measure the giant spin-dependent shift of the beam centroid produced by the metamaterial at a visible wavelength. Our results suggest that the structured metamaterial offers a potential method of manipulating spin-polarized photons and the orbital angular momentum of light and thus enables applications in spin-controlled nanophotonics. Keywords: geometric phase; metamaterial; photonic spin Hall effect INTRODUCTION Metamaterials or metasurfaces are artificial materials that are engineered to produce nearly any imaginable optical properties that are not found in nature. 1,2 They are typically structured at the subwavelength scale with ultrathin metallic or dielectric micro/nanoparticles or with holes opened in metallic films. Metamaterials exhibit unprecedented degrees of freedom in the polarization and phase manipulation of light via the geometric structuring of their structural units, especially on the wavelength scale, 3-9 which leads to applications such as vortex beam generators, 3,7 metalenses 10,11 and optical holography. 12,13 These materials also offer considerable potential for the manipulation of the angular moment of light and the photonic spin Hall effect (SHE), thereby providing convenient opportunities for spin-polarized photonics and nanophotonics. [14][15][16][17] The photonic SHE describes the mutual influence of the photon spin (polarization) and the trajectory (orbital angular momentum) of light-beam propagation, i.e., the spin-orbit interaction (SOI), which results in two types of geometric phases: the Rytov-VladimirskiiBerry (RVB) phase and the Pancharatnam-Berry (PB) phase. [18][19][20][21][22] The RVB phase is associated with the evolution of the propagation direction of light. When a light beam reflects/refracts at a planar interface between different media, a SOI occurs, and the corresponding momentum-dependent RVB phase leads to a spin-dependent real-

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Ultra-thin plasmonic optical vortex plate based on phase discontinuities

Cited by 478 publications

References 18 publications

Ultra-thin, planar, Babinet-inverted plasmonic metalenses

Ultra-thin, planar, Babinet-inverted plasmonic metalenses

Generating optical orbital angular momentum at visible wavelengths using a plasmonic metasurface

Giant photonic spin Hall effect in momentum space in a structured metamaterial with spatially varying birefringence

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