Spontaneous Emission of Vector Vortex Beams

Abstract

Harnessing the spontaneous emission of incoherent quantum emitters is one of the hallmarks of nano-optics. Yet, an enduring challenge remains-making them emit vector beams, which are complex forms of light associated with fruitful developments in fluorescence imaging, optical trapping and high-speed telecommunications. Vector beams are characterized by spatially varying polarization states whose construction requires coherence properties that are typically possessed by lasers-but not by photons produced by spontaneous emission. Here, we show a route to weave the spontaneous emission of an ensemble of colloidal quantum dots into vector beams. To this end, we use holographic nanostructures that impart the necessary spatial coherence, polarization and topological properties to the light originating from the emitters. We focus our demonstration on vector vortex beams, which are chiral vector beams carrying non-zero orbital angular momentum, and argue that our approach can be extended to other forms of vectorial light.

Shaping the spontaneous emission of extended incoherent sources into composite radial vector beams

“…We corroborate these observations with a scalar model originally developed to explain the formation of vector vortex beams in Ref. [19]. This model assumes that the PbS NCs excited by the focused laser spot act as a single point source from which a cylindrical wave is launched:…”

“…2(e)]. As elaborated elsewhere 19 , this beam is a vector vortex beam with a topological charge equal to the number of branches of the spiral. Away from the center, the back focal plane images reveal the formation of arcs whose orientation depends on the position of the point excitation.…”

“…We begin our study by extending some results of the literature to the three-branch spiral of Fig. 1(a)-a variant of the bull's eye geometry that we have already used in a previous article to demonstrate the spontaneous emission of vector vortex beams 19 . The radial period is 1235 nm, the height of the corrugations is 25 nm and the total footprint of the structure is a disk of 100 µm.…”

Making Quantum Emitters Emit Vector Vortex Beams

“…Due to the dispersive nature of our structure, the diameter of the ring changes with the wavelength filter, as discussed in Ref. [6] for vector vortex beams with higher topological charges (NB: the results presented in this paper are fully original). We have also established an analytical model that calculates the intensity and phase distribution of the far-field diffraction pattern in the scalar Fraunhofer approximation.…”

Single-shot characterization of vector beams by generalized measurements

“…Polarization is one of the key properties of light, affecting the propagation and scattering of optical beams and providing a convenient degree of freedom for classical and quantum communication. While laser beams typically have homogeneous polarization profiles, recent years have seen an increasing interest in light designed with spatially varying polarization structures, including vector vortex beams [1][2][3][4][5], Poincaré beams [6][7][8] and even skyrmionic beams [9,10]. These vector beams are characterized by non-separable correlations between their polarization and spatial degree of freedom [11,12], with intriguing applications for quantum [13][14][15][16] and quantum inspired protocols [17][18][19][20][21][22][23].…”