Optical vortices from closed-loop subwavelength slits

International audienceWe report on the singular shaping of light using closed-loop subwavelength slits whose shape is homeomorphic to the circle. Various sets of optical phase singularities can be generated depending on the given closed path whose geometry tailors the spin-orbit interaction for the light that passes through the curved slit. Here three families of closed-loop curves are considered--polygons, hypocycloids, and epicycloids

Comment on "Low-Power Laser Deformation of an Air-Liquid Interface"

International audienceRecently, the observation of low-power laser deformation of an air-water horizontal interface under total internal reflection (TIR) was argued [1]. This effect was claimed to be independent of the incident light-beam power andthe interfacial tension and explained by a model that (i) accounts for the existence of a nonzero in-plane component of the optical radiation pressure exerted on the air-water interface, which was ascribed to the Goos-Hänchen spatial shift—a characteristic feature of TIR—and (ii) does not account for the force balance at the air-water interface. This Comment aims at correcting these two points

Taming the swirl of self-structured liquid crystal q-plates

International audienceSpontaneously formed liquid crystal topological defects under external fields offer a nature-assisted route to the creation of geometric phase optical vortex generators (q-plates). Here we report on the consequences of the unavoidable swirled transverse spatial distribution of the optical axis of such optical elements on the beam shaping and we propose a swirl-compensation scheme based on the arithmetic of geometric phase optical elements

Pure and achromatic spin-orbit shaping of light from Fresnel reflection off space-variant anisotropic media

International audienceWe propose an approach to achieve achromatic pure geometric phase shaping of light from anisotropic media by exploiting the fundamental laws of electromagnetic waves. Its practical implementation requires a cover layer made of a dispersive isotropic medium. The approach applies to any anisotropic material and any geometric phase spatial distribution and preserves the geometric phase reversal upon the reversal of the incident polarization handedness. An experimental demonstration is made over the whole visible range but can be extended to any wavelength range without conceptual issues

Dielectric geometric phase optical elements from femtosecond direct laser writing

We propose to use femtosecond direct laser writing technique to realize dielectric optical elements from photo-resist materials for the generation of structured light from purely geometrical phase transformations. This is illustrated by the fabrication and characterization of spin-to-orbital optical angular momentum couplers generating optical vortices of topological charge from 1 to 20. In addition, the technique is scalable and allows obtaining microscopic to macroscopic flat optics. These results thus demonstrate that direct 3D photopolymerization technology qualifies for the realization of spin-controlled geometric phase optical elements.Comment: 6 figure

Self-induced liquid crystal q-plate by photoelectric interface activation

International audienceHere, we report on the experimental demonstration that highly efficient self-induced spin-orbit optical vortex generation can be achieved by using standard liquid crystal materials and surface treatment agents. This is done by revisiting the recent attempt by Zolot’ko and coworkers to produce self-induced liquid crystal vortex plates using the dc electric field [I. A. Budagovsky, S. A. Shvetsov, and A. S. Zolot’ko, Mol. Cryst. Liq. Cryst. 637, 47 (2016)] that remains, so far, limited to moderate efficiencies. The phenomenon is the result of the self-back-action of light arising from the spontaneous creation of a liquid crystal topological defect. These results demonstrate photo-electric interface activation as a candidate towards the development of a self-adapted spinorbit photonic toolbox, thus enabling agile management of the orbital angular momentum of light

Light-driven liquid crystalline nonlinear oscillator under optical periodic forcing

An all-optically driven strategy to govern a liquid crystalline collective molecular nonlinear oscillator is discussed. It does not require external feedbacks of any kind while the oscillator and a time-depending perturbation both are sustained by incident light. Various dynamical regimes such as frequency -locked, quasiperiodic, forced and chaotic are observed in agreement with a theoretical approach developed in the limit of the plane wave approximation.Comment: 5 pages, 6 figures, submitted to Phys. Rev.

All-optical switching and multistability in photonic structures with liquid crystal defects

We demonstrate that one-dimensional photonic crystals with pure nematic liquid-crystal defects can operate as all-optical switching devices based on optical orientational nonlinearities of liquid crystals. We show that such a periodic structure is responsible for a modulated threshold of the optical Fr\'eedericksz transition in the spectral domain, and this leads to all-optical switching and light-induced multistability. This effect has no quasi-statics electric field analogue, and it results from nonlinear coupling between light and a defect mode.Comment: 4 pages, 3 figure