Chirality is one of the most prominent and intriguing aspects of nature, from spiral galaxies down to aminoacids. Despite the wide range of living and non-living, natural and artificial chiral systems at different scales, the origin of chirality-induced phenomena is often puzzling. Here we assess the onset of chiral optomechanics, exploiting the control of the interaction between chiral entities. We perform an experimental and theoretical investigation of the simultaneous optical trapping and rotation of spherulite-like chiral microparticles. Due to their shell structure (Bragg dielectric resonator), the microparticles function as omnidirectional chiral mirrors yielding highly polarization-dependent optomechanical effects. The coupling of linear and angular momentum, mediated by the optical polarization and the microparticles chiral reflectance, allows for fine tuning of chirality-induced optical forces and torques. This offers tools for optomechanics, optical sorting and sensing and optofluidics.

Low-scattering and highly efficient orientational gratings are obtained, exploiting polarization holography to modulate the in-plane anchoring axis at both surfaces of a planar nematic cell. Polarization-sensitive azo-dye-doped polyimide films are used as aligning layers. For proper values of cell thickness and spatial periodicity of the gratings, the director configuration in the nematic bulk is a perfect replica of the polarization gratings recorded on the aligning layers. High first-order diffraction efficiency, up to 98%, is observed in thin grating regime. External ac voltage allows to adjust the efficiency over the whole range for arbitrary cell thickness.

Two-dimensional (2D) gratings made up of an array of differently twisted nematic structures are obtained by crossed assembling of 1D polarization holograms recorded at the photoaligning substrates. The rotating linear polarization pattern, produced by the interference of two opposite circularly polarized beams, is recorded on the azo-dye doped polyimide aligning layers. The 2D gratings diffract light in different directions with different polarization states, that can be optically controlled. Orthogonal circularly and linearly polarized diffraction orders are simultaneously obtained irradiating the grating with a linearly polarized beam. An external ac voltage allows to completely control the diffracted energy distribution.

Photoinduced supramolecular chiral structures in amorphous and nonchiral azo copolymer are demonstrated using circularly polarized light. The polymeric film undergoes a light-guided inhomogeneous supramolecular modification, both in the transverse and longitudinal directions. The photoinduced structure strongly affects the polarization state of the light propagating in it. Conversion from circular toward linear polarization occurs, and optical activity of the material arises. The direction of the optical rotation (clockwise or anticlockwise) can be controlled by means of the handedness of the inducing CPL. The resulting chiral structures, circular and spiral, exhibits interesting possibility to manipulate the light polarization, showing long-time stability and full reconfigurability.