Asymmetric topological pumping in nonparaxial photonics

Topological photonics was initially inspired by the quantum-optical analogy between the Schrödinger equation for an electron wavefunction and the paraxial equation for a light beam. Here, we reveal an unexpected phenomenon in topological pumping observed in arrays of nonparaxial optical waveguides where the quantum-optical analogy becomes invalid. We predict theoretically and demonstrate experimentally an asymmetric topological pumping when the injected field transfers from one side of the waveguide array to the other side whereas the reverse process is unexpectedly forbidden. Our finding could open an avenue for exploring topological photonics that enables nontrivial topological phenomena and designs in photonics driven by nonparaxiality.

Controllable shifting, steering, and expanding of light beam based on multi-layer liquid-crystal cells

Shaping and steering of light beams is essential in many modern applications, ranging from optical tweezers, camera lenses, vision correction to 3D displays. However, current realisations require increasingly greater tunability and aim for lesser specificity for use in diverse applications. Here, we demonstrate tunable light beam control based on multi-layer liquid-crystal cells and external electric field, capable of extended beam shifting, steering, and expanding, using a combination of theory and full numerical modelling, both for liquid crystal orientations and the transmitted light. Specifically, by exploiting three different function-specific and tunable birefringent nematic layers, we show an effective liquid-crystal beam control device, capable of precise control of outgoing light propagation, with possible application in projectors or automotive headlamps.

LIGHT CAPTURING WITHIN THE DEFECT LOCATED IN LINEAR ONE-DIMENSIONAL PHOTONIC LATTICE

Numerically investigated the light beam propagation through one-dimensional photonic lattice possessing one linear defect. It is shown how capturing of light depends on lattice characteristics as well as the width and wavelength of input light beam. Results may be useful for all-optical control of transmission of waves in interferometry.

Improving the safety of train lighting devices in curves

The article presents a system for correcting the direction of the light beam of a rolling stock searchlight in curved sections of the track. The dependence of the angle of deviation of the axis of the light beam of the searchlight on the angle of inclination of the trolley is determined. The principle of correction of the light beam of a rolling stock searchlight using a matrix LED searchlight is described.