Chiral nanoemitter array: A launchpad for optical vortices

Abstract

A chiral arrangement of molecular nanoemitters is shown to support delocalised exciton states whose spontaneous decay can generate optical vortex radiation. In contrast to techniques in which phase modification is imposed upon conventional optical beams, this exciton method enables radiation with a helical wave-front to be produced directly. To achieve this end, a number of important polarisation and symmetry-based criteria need to be satisfied. It emerges that the phase structure of the optical field produced by degenerate excitons in a propeller-shaped array can exhibit precisely the sought character of an optical vortex -one with unit topological charge. Practical considerations for the further development of this technique are discussed, and potential new applications are identified.

Roadmap on structured light

“…For example, while the continued development of q-plates and SLMs paves the way for more precise tailoring of optical beam structures, the most welcome development would be a turnkey laser system for directly delivering beams with aprogrammable structure,ideally one with tailored fibre optic beam delivery. 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. Addressing the intriguing postulate that twisted beams might indirectly induce nuclear hyperpolarization for magnetic resonance applications is another quest that requires an especially clever integration of nuclear magnetic resonance and laser instrumentation [22].…”

Nanoarrays for the generation of complex optical wave-forms

“…The theoretical basis for the direct generation of an optical vortex beam is based on a structured array composed of a number of nanoemitters; [10][11][12] for the purposes of this paper, the number chosen is five. By adopting such an array with a geometric configuration shown in Figure 1, it is possible to exploit phase relationships between the quantum amplitudes associated with emission from differing positions.…”

Optical vortex mode generation by nanoarrays with a tailored geometry

“…17 If the base of the cylinder is rotated relative to the top, the connectors adopt a slanted configuration; taking a cross-section of this construct provides the essence of the dipole orientation required in the following, as illustrated in Figure 1. We focus on the general case of three or more (n) such emitters, centered upon a rotational symmetry axis of order n. 18 [Two nanoemitters may generate a planar phase discontinuity, but vortex emission is not possible for such a case.] 19 This configuration confers precisely equivalent electronic coupling between each adjacent pair, on the assumption that there is negligible interaction with potentially less highly symmetric surroundings.…”