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

By Ebrahim Karimi, Sebastian A. Schulz, Israel De Leon, Hammam Qassim, Jeremy Upham, R. W. Boyd. Light: Science & Applications, 2014

779 citations recorded by the source corpus.

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 ±2ħ (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. Visible, circularly polarised light can be transformed into light-carrying orbital angular momentum by a plasmonic metasurface. That is the finding of Ebrahim Karimi and co-workers at the University of Ottawa in Canada and the University of Rochester in the United States. Light with orbital angular momentum (owing to a twisted phase front) is traditionally generated using specially designed optical elements such as spatial light modulator, cylindrical lens mode converters and q-plate. The researchers have now shown that a plasmonic metasurface comprising an array of nano-antennas can couple spin-to-orbital angular momentum at thickness much smaller than the wavelength of the light with an efficiency of around 3%. The conversion takes place due to the birefringence present in the nanostructure array. This approach could yield ultrathin generators of visible light with orbital angular momentum, for potential applications in spectroscopy, imaging, sensing and quantum information.

Subfields: Atomic and Molecular Physics, and Optics, Biomedical Engineering, Electronic, Optical and Magnetic Materials

View Paper: https://www.semanticscholar.org/paper/f63d3594b3754f48428c4fc887ee9a45a1456726

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Citations in the corpus

Optical communications using orbital angular momentum beams (2015, neutral): “A compact metasurface could be made into a phase plate by manipulating the spatial phase response caused by the structure [24,25].”
Roadmap on structured light (2016, background): “But even to explore the possibility of directly generating structured light, as for example from molecular arrays [19] or specifically tailored plasmonic metasurfaces [20, 21], already places high demands on current nanofabrication facilities.”
Electron vortices: Beams with orbital angular momentum (2017, methodology): “…as a method of generating useful electron vortices - however, conversely the q-filter may be used with l = ±1 vortex beam and appropriate apertures and OAM sorters to 26 obtain non-vortex spin-polarised electron probes for various applications (Grillo et al., 2013; Karimi et al., 2012, 2014).”
Twisted photons: new quantum perspectives in high dimensions (2017, neutral): “Due to limitation of space, we cannot cover breakthrough experiments in the area of high-dimensional quantum information memories [6, 7], in highdimensional quantum information processing with other physical systems [8–11], coherent transitions of atomic states driven by the OAM of photons [12] or n”